public PollySqlConnection(string connectionString, IAsyncPolicy[] asyncPolicies, ISyncPolicy[] syncPolicies)
{
_connectionString = connectionString;
_asyncPolicies = asyncPolicies;
_syncPolicies = syncPolicies;
if (asyncPolicies == null)
{
throw new ArgumentNullException($"{nameof(asyncPolicies)} must have at least one async policy provided");
}
if (asyncPolicies.Length == 1)
{
_singleAsyncPolicy = asyncPolicies[0];
}
else
{
_asyncPolicyWrapper = Policy.WrapAsync(asyncPolicies);
}
if (syncPolicies == null)
{
throw new ArgumentNullException($"{nameof(syncPolicies)} must have at least one sync policy provided");
}
if (syncPolicies.Length == 1)
{
_singleSyncPolicy = syncPolicies[0];
}
else
{
_syncPolicyWrapper = Policy.Wrap(syncPolicies);
}
_connection = new SqlConnection(connectionString);
}
private async Task <FaceDetectResult[]> MakeFaceIdentifyRequest(FaceIdentifyRequest req, string apiKey, Guid requestId, PolicyWrap <HttpResponseMessage> policy)
{
string strResult = string.Empty;
StringBuilder faceids = new StringBuilder();
req.FaceIds.ToList().ForEach(s => faceids.Append(s + " "));
_log.Info($"Making identify request faceids: {faceids} requestId: {requestId} apiKey:{apiKey} ticks: {DateTime.Now.Ticks}");
FaceDetectResult[] result = null;
// Get the API URL and the API key from settings.
var uri = ConfigurationManager.AppSettings["faceIdentifyApiUrl"];
// Configure the HttpClient request headers.
_client.DefaultRequestHeaders.Clear();
_client.DefaultRequestHeaders.Accept.Clear();
_client.DefaultRequestHeaders.Add("Ocp-Apim-Subscription-Key", apiKey);
//_client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
try
{
// Execute the REST API call, implementing our resiliency strategy.
HttpResponseMessage response = await policy.ExecuteAsync(() => _client.PostAsync(uri, FaceHelper.GetIdentifyHttpContent(req)));
// Get the JSON response.
strResult = await response.Content.ReadAsStringAsync();
result = await response.Content.ReadAsAsync <FaceDetectResult[]>();
_log.Info($"identify completed: {strResult} requestId: {requestId} apiKey:{apiKey} ticks: {DateTime.Now.Ticks}");
}
catch (BrokenCircuitException bce)
{
_log.Error($"Could not contact the Face API service due to the following error: {bce.Message} requestId: {requestId} apiKey:{apiKey} ticks: {DateTime.Now.Ticks}", bce);
}
catch (Exception e)
{
_log.Error($"Critical error-MakeFaceIdentifyRequest: {e.Message} requestId: {requestId} apiKey:{apiKey} string result:{strResult} ticks: {DateTime.Now.Ticks}", e);
}
return(result);
}
/// <summary>
/// Register instance in DI.
/// </summary>
/// <typeparam name="TClient">Interface implemented by a type.</typeparam>
/// <typeparam name="TImplementation">A type implements TClient interface.</typeparam>
/// <param name="services">instance of IServiceCollection.</param>
/// <param name="policy">circuit breaker policy.</param>
public static void RegisterInstace <TClient, TImplementation>(this IServiceCollection services, PolicyWrap <HttpResponseMessage> policy)
where TClient : class
where TImplementation : class, TClient
{
PolicyBuilder policyBuilder = new PolicyBuilder();
services.AddHttpClient <TClient, TImplementation>()
.AddPolicyHandler(t => { return(policy); })
.CorrelateRequests("X-Correlation-ID")
.ConfigurePrimaryHttpMessageHandler(() => new HttpClientHandler()
{
AllowAutoRedirect = false,
AutomaticDecompression = DecompressionMethods.Deflate | DecompressionMethods.GZip
});
}
public override async Task ExecuteAsync(CancellationToken cancellationToken, IProgress <DemoProgress> progress)
{
if (cancellationToken == null)
{
throw new ArgumentNullException(nameof(cancellationToken));
}
if (progress == null)
{
throw new ArgumentNullException(nameof(progress));
}
// Let's call a web api service to make repeated requests to a server.
// The service is programmed to fail after 3 requests in 5 seconds.
eventualSuccesses = 0;
retries = 0;
eventualFailuresDueToTimeout = 0;
eventualFailuresForOtherReasons = 0;
progress.Report(ProgressWithMessage(typeof(AsyncDemo09_Wrap_Fallback_Timeout_WaitAndRetry).Name));
progress.Report(ProgressWithMessage("======"));
progress.Report(ProgressWithMessage(String.Empty));
Stopwatch watch = null;
// Define our timeout policy: time out after 2 seconds. We will use the pessimistic timeout strategy, which forces a timeout - even when the underlying delegate doesn't support it.
var timeoutPolicy = Policy
.TimeoutAsync(TimeSpan.FromSeconds(2), TimeoutStrategy.Pessimistic);
// Define our waitAndRetry policy: keep retrying with 4 second gaps. This is (intentionally) too long: to demonstrate that the timeout policy will time out on this before waiting for the retry.
var waitAndRetryPolicy = Policy
.Handle <Exception>() // Exception filtering! We don't retry if the inner circuit-breaker judges the underlying system is out of commission!
.WaitAndRetryForeverAsync(
attempt => TimeSpan.FromSeconds(4),
(exception, calculatedWaitDuration) =>
{
progress.Report(ProgressWithMessage(".Log,then retry: " + exception.Message, Color.Yellow));
retries++;
});
// Define a fallback policy: provide a nice substitute message to the user, if we found the call was rejected due to the timeout policy.
FallbackPolicy <String> fallbackForTimeout = Policy <String>
.Handle <TimeoutRejectedException>()
.FallbackAsync(
fallbackValue: /* Demonstrates fallback value syntax */ "Please try again later [Fallback for timeout]",
onFallbackAsync: async b =>
{
await Task.FromResult(true);
watch.Stop();
progress.Report(ProgressWithMessage("Fallback catches failed with: " + b.Exception.Message + " (after " + watch.ElapsedMilliseconds + "ms)", Color.Red));
eventualFailuresDueToTimeout++;
}
);
// Define a fallback policy: provide a substitute string to the user, for any exception.
FallbackPolicy <String> fallbackForAnyException = Policy <String>
.Handle <Exception>()
.FallbackAsync(
fallbackAction: /* Demonstrates fallback action/func syntax */ async ct =>
{
await Task.FromResult(true);
/* do something else async if desired */
return("Please try again later [Fallback for any exception]");
},
onFallbackAsync: async e =>
{
await Task.FromResult(true);
watch.Stop();
progress.Report(ProgressWithMessage("Fallback catches eventually failed with: " + e.Exception.Message + " (after " + watch.ElapsedMilliseconds + "ms)", Color.Red));
eventualFailuresForOtherReasons++;
}
);
// Compared to previous demo08: here we use *instance* wrap syntax, to wrap all in one go.
PolicyWrap <String> policyWrap = fallbackForAnyException.WrapAsync(fallbackForTimeout).WrapAsync(timeoutPolicy).WrapAsync(waitAndRetryPolicy);
using (var client = new HttpClient())
{
totalRequests = 0;
bool internalCancel = false;
while (!internalCancel && !cancellationToken.IsCancellationRequested)
{
totalRequests++;
watch = new Stopwatch();
watch.Start();
try
{
// Manage the call according to the whole policy wrap
string response = await policyWrap.ExecuteAsync(ct =>
client.GetStringAsync(Configuration.WEB_API_ROOT + "/api/values/" + totalRequests), cancellationToken);
watch.Stop();
progress.Report(ProgressWithMessage("Response: " + response + "(after " + watch.ElapsedMilliseconds + "ms)", Color.Green));
eventualSuccesses++;
}
catch (Exception e) // try-catch not needed, now that we have a Fallback.Handle<Exception>. It's only been left in to *demonstrate* it should never get hit.
{
throw new InvalidOperationException("Should never arrive here. Use of fallbackForAnyException should have provided nice fallback value for any exceptions.", e);
}
// Wait half second
await Task.Delay(TimeSpan.FromSeconds(0.5), cancellationToken);
internalCancel = TerminateDemosByKeyPress && Console.KeyAvailable;
}
}
}
public static async Task ExecuteAsync(CancellationToken cancellationToken)
{
Console.WriteLine(typeof(AsyncDemo07_WaitAndRetryNestingCircuitBreakerUsingPolicyWrap).Name);
Console.WriteLine("=======");
// Let's call a web api service to make repeated requests to a server.
// The service is programmed to fail after 3 requests in 5 seconds.
var client = new HttpClient();
int eventualSuccesses = 0;
int retries = 0;
int eventualFailuresDueToCircuitBreaking = 0;
int eventualFailuresForOtherReasons = 0;
// Define our waitAndRetry policy: keep retrying with 200ms gaps.
var waitAndRetryPolicy = Policy
.Handle <Exception>(e => !(e is BrokenCircuitException)) // Exception filtering! We don't retry if the inner circuit-breaker judges the underlying system is out of commission!
.WaitAndRetryForeverAsync(
attempt => TimeSpan.FromMilliseconds(200),
(exception, calculatedWaitDuration) =>
{
// This is your new exception handler!
// Tell the user what they've won!
ConsoleHelper.WriteLineInColor(".Log,then retry: " + exception.Message, ConsoleColor.Yellow);
retries++;
});
// Define our CircuitBreaker policy: Break if the action fails 4 times in a row.
var circuitBreakerPolicy = Policy
.Handle <Exception>()
.CircuitBreakerAsync(
exceptionsAllowedBeforeBreaking: 4,
durationOfBreak: TimeSpan.FromSeconds(3),
onBreak: (ex, breakDelay) =>
{
ConsoleHelper.WriteLineInColor(".Breaker logging: Breaking the circuit for " + breakDelay.TotalMilliseconds + "ms!", ConsoleColor.Magenta);
ConsoleHelper.WriteLineInColor("..due to: " + ex.Message, ConsoleColor.Magenta);
},
onReset: () => ConsoleHelper.WriteLineInColor(".Breaker logging: Call ok! Closed the circuit again!", ConsoleColor.Magenta),
onHalfOpen: () => ConsoleHelper.WriteLineInColor(".Breaker logging: Half-open: Next call is a trial!", ConsoleColor.Magenta)
);
// New for demo07: combine the waitAndRetryPolicy and circuitBreakerPolicy into a PolicyWrap.
PolicyWrap policyWrap = Policy.WrapAsync(waitAndRetryPolicy, circuitBreakerPolicy);
int i = 0;
// Do the following until a key is pressed
while (!Console.KeyAvailable && !cancellationToken.IsCancellationRequested)
{
i++;
Stopwatch watch = new Stopwatch();
watch.Start();
try
{
// Retry the following call according to the policy wrap
string msg = await policyWrap.ExecuteAsync <String>(ct =>
{
// This code is executed through both policies in the wrap: WaitAndRetry outer, then CircuitBreaker inner. Demo 06 shows a broken-out version of what this is equivalent to.
return(client.GetStringAsync(Configuration.WEB_API_ROOT + "/api/values/" + i));
}, cancellationToken);
watch.Stop();
// Display the response message on the console
ConsoleHelper.WriteInColor("Response : " + msg, ConsoleColor.Green);
ConsoleHelper.WriteLineInColor(" (after " + watch.ElapsedMilliseconds + "ms)", ConsoleColor.Green);
eventualSuccesses++;
}
catch (BrokenCircuitException b)
{
watch.Stop();
ConsoleHelper.WriteInColor("Request " + i + " failed with: " + b.GetType().Name, ConsoleColor.Red);
ConsoleHelper.WriteLineInColor(" (after " + watch.ElapsedMilliseconds + "ms)", ConsoleColor.Red);
eventualFailuresDueToCircuitBreaking++;
}
catch (Exception e)
{
watch.Stop();
ConsoleHelper.WriteInColor("Request " + i + " eventually failed with: " + e.Message, ConsoleColor.Red);
ConsoleHelper.WriteLineInColor(" (after " + watch.ElapsedMilliseconds + "ms)", ConsoleColor.Red);
eventualFailuresForOtherReasons++;
}
// Wait half second
await Task.Delay(TimeSpan.FromSeconds(0.5), cancellationToken);
}
Console.WriteLine("");
Console.WriteLine("Total requests made : " + i);
Console.WriteLine("Requests which eventually succeeded : " + eventualSuccesses);
Console.WriteLine("Retries made to help achieve success : " + retries);
Console.WriteLine("Requests failed early by broken circuit : " + eventualFailuresDueToCircuitBreaking);
Console.WriteLine("Requests which failed after longer delay: " + eventualFailuresForOtherReasons);
}
public RpdClient(RpdNetworkConfig config)
{
this.config = config;
this.client = new RestClient(config.BaseUrl);
this.policy = RestPolicy.DefaultPolicy(config.RetryAttempts, config.TimeOut);
}
public static async Task <HttpResponseMessage> Run([HttpTrigger(AuthorizationLevel.Function, "get", "post", Route = null)] HttpRequestMessage req, TraceWriter log)
{
Guid requestID = Guid.NewGuid();
try
{
log.Info($"LoadPersonGroup was triggered request id {requestID}");
string largepersongroupid = req.GetQueryNameValuePairs()
.FirstOrDefault(q => string.Compare(q.Key, "groupid", true) == 0)
.Value;
if (largepersongroupid == null)
{
// Get request body
dynamic data = await req.Content.ReadAsAsync <object>();
largepersongroupid = data?.groupid;
}
if (largepersongroupid != null)
{
string apis = ConfigurationManager.AppSettings["apis"];
string[] apiArr = apis.Split(',');
if (apiArr.Length > 0)
{
_loadPersonClient = _loadPersonClient ?? new HttpClient();
PolicyWrap <HttpResponseMessage> resilientPolicy = FaceHelper.DefineAndRetrieveResiliencyStrategy(log);
int i;
//setting the map of api to database in database 1
IDatabase cache = Connection.GetDatabase(1);
for (i = 1; i <= apiArr.Length; i++)
{
cache.StringSet(apiArr[i - 1], i + 1);
}
var personResult = new ListPersonGroup(log, _loadPersonClient);
for (i = 1; i <= apiArr.Length; i++)
{
bool isComplete = false;
string lastPerson = string.Empty;
Task <InternalPersonDetails[]> task;
List <InternalPersonDetails> personList = new List <InternalPersonDetails>();
cache = Connection.GetDatabase(i + 1);
while (!isComplete)
{
task = personResult.GetListPersonGroup(lastPerson, apiArr[i - 1], largepersongroupid, requestID, resilientPolicy);
task.Wait();
if (task.Result.Length < 1000)
{
isComplete = true;
}
if (task.Result.Length > 0)
{
lastPerson = task.Result[task.Result.Length - 1].PersonId.ToString();
personList.AddRange(task.Result.ToList());
}
int loop = task.Result.Length / 100;
var tmplist = task.Result.ToList();
int k = 0, len = 0;
for (k = 0; k < loop; k++)
{
var tmpinnerlist = tmplist.GetRange(k * 100, 100);
len += tmpinnerlist.Count;
cache.StringSet(tmpinnerlist.Select(s =>
new KeyValuePair <RedisKey, RedisValue>(largepersongroupid + "-" + s.PersonId, s.Name)).ToArray(), When.Always);
}
if (tmplist.Count - len > 0)
{
var tmpinnerlist = tmplist.GetRange(k * 100, tmplist.Count - len);
cache.StringSet(tmpinnerlist.Select(s =>
new KeyValuePair <RedisKey, RedisValue>(largepersongroupid + "-" + s.PersonId, s.Name)).ToArray(), When.Always);
}
}
}
return(req.CreateResponse(HttpStatusCode.OK, "Redis loaded successfully"));
}
else
{
string msg = "List of Api setting is empty";
log.Error($"Error-LoadPersonGroup: {msg} requestId: {requestID} ticks: {DateTime.Now.Ticks}");
return(req.CreateResponse(HttpStatusCode.BadRequest, "List of Api setting is empty"));
}
}
else
{
string msg = "Please pass a large person group id on the query string or in the request body";
log.Error($"Error-LoadPersonGroup: {msg} requestId: {requestID} ticks: {DateTime.Now.Ticks}");
return(req.CreateResponse(HttpStatusCode.BadRequest, msg));
}
}
catch (Exception e)
{
log.Error($"Exception-LoadPersonGroup: {e.Message} requestId: {requestID} ticks: {DateTime.Now.Ticks}", e);
return(req.CreateResponse(HttpStatusCode.BadRequest, e.Message));
}
}
public async Task <InternalPersonDetails[]> GetListPersonGroup(string startPerson, string apiKey, string largegroupid, Guid requestId, PolicyWrap <HttpResponseMessage> policy)
{
return(await MakeListPersonGroupRequest(startPerson, apiKey, largegroupid, requestId, policy));
}
public static List <TestUser> GetUsers()
{
//Retry untill other side return users successfull,
//After 3 tries, just return John Doe...
//Fallback policy -> create John Doe
PolicyWrap <List <TestUser> > policy = CreateWaitPolicy();
var users = GetTimeRegistrationDemoUsers();
users.Wait(50000);
var testUsers = users.Result.Users.Select(x =>
new TestUser
{
SubjectId = x.Id.ToString(),
Username = x.FirstName,
Password = x.LastName,
Claims = new List <Claim>
{
new Claim("name", x.FirstName + " " + x.LastName),
new Claim("role", x.Roles.FirstOrDefault().Id)
}
}
).ToList();
return(testUsers);
//return new List<TestUser>
//{
// new TestUser
// {
// SubjectId = "50",
// Username = "******",
// Password = "******",
// Claims = new List<Claim>
// {
// new Claim("name", "jef"),
// new Claim("role","Employee")
// }
// },
// new TestUser
// {
// SubjectId = "1",
// Username = "******",
// Password = "******",
// Claims = new List<Claim>
// {
// new Claim("name", "alice"),
// new Claim("website", "https://alice.com"),
// new Claim("role","Administrators")
// }
// },
// new TestUser
// {
// SubjectId = "2",
// Username = "******",
// Password = "******",
// Claims = new List<Claim>
// {
// new Claim("name", "bob"),
// new Claim("website", "https://bob.com"),
// new Claim("role","Managers")
// }
// }
//};
}
public void AddPolicy(string origin, PolicyWrap policy)
{
}
public T Execute<T>(Func<T> operation, Func<T> openStateOperation)
{
// Define our waitAndRetry policy: keep retrying with n ms gaps.
RetryPolicy waitAndRetryPolicy = Policy
.Handle<Exception>(e => !(e is BrokenCircuitException)) // Exception filtering! We don't retry if the inner circuit-breaker judges the underlying system is out of commission!
.WaitAndRetryForever(
attempt => TimeSpan.FromMilliseconds(SiteSettings.Instance.SleepDurationsMilliseconds),
(exception, calculatedWaitDuration) =>
{
_log.Error(".Log, then retry: ", exception);
});
// Define our CircuitBreaker policy: Break if the action fails n times in a row.
CircuitBreakerPolicy circuitBreakerPolicy = Policy
.Handle<Exception>()
.CircuitBreaker(
exceptionsAllowedBeforeBreaking: SiteSettings.Instance.ExceptionsAllowedBeforeBreaking,
durationOfBreak: TimeSpan.FromSeconds(1),
onBreak: (ex, breakDelay) =>
{
_log.Error($".Breaker logging: Breaking the circuit for {breakDelay.TotalMilliseconds} + ms!");
_log.Error($"..due to: {ex.Message}");
},
onReset: () =>
{
_log.Error(".Breaker logging: Call ok! Closed the circuit again!");
},
onHalfOpen: () =>
{
_log.Error(".Breaker logging: Half-open: Next call is a trial!");
}
);
// Define a fallback policy: provide a secondary services or substitute result to the user, for any exception.
FallbackPolicy<T> fallbackForAnyException = Policy<T>
.Handle<Exception>()
.Fallback(
fallbackAction: openStateOperation,
onFallback: e =>
{
_log.Error($"Fallback catches eventually failed with: {e.Exception.Message}");
}
);
// We combine the waitAndRetryPolicy and circuitBreakerPolicy into a PolicyWrap, using the *static* Policy.Wrap syntax.
PolicyWrap myResilienceStrategy = Policy.Wrap(waitAndRetryPolicy, circuitBreakerPolicy);
// We wrap the two fallback policies onto the front of the existing wrap too. And the fact that the PolicyWrap myResilienceStrategy from above is just another Policy, which can be onward-wrapped too.
// With this pattern, you can build an overall resilience strategy programmatically, reusing some common parts (eg PolicyWrap myResilienceStrategy) but varying other parts (eg Fallback) individually for different calls.
PolicyWrap<T> policyWrap = fallbackForAnyException.Wrap(myResilienceStrategy);
try
{
// Manage the call according to the whole policy wrap.
var response =
policyWrap.Execute(operation);
return response;
}
catch (Exception e) // try-catch not needed, now that we have a Fallback.Handle<Exception>. It's only been left in to *demonstrate* it should never get hit.
{
_log.Error("Should never arrive here. Use of fallbackForAnyException should have provided nice fallback value for any exceptions.", e);
return default(T);
}
}
public override void Execute(CancellationToken cancellationToken, IProgress <DemoProgress> progress)
{
if (cancellationToken == null)
{
throw new ArgumentNullException(nameof(cancellationToken));
}
if (progress == null)
{
throw new ArgumentNullException(nameof(progress));
}
// Let's call a web api service to make repeated requests to a server.
// The service is programmed to fail after 3 requests in 5 seconds.
eventualSuccesses = 0;
retries = 0;
eventualFailuresDueToTimeout = 0;
eventualFailuresForOtherReasons = 0;
progress.Report(ProgressWithMessage(typeof(Demo09_Wrap_Fallback_Timeout_WaitAndRetry).Name));
progress.Report(ProgressWithMessage("======"));
progress.Report(ProgressWithMessage(String.Empty));
Stopwatch watch = null;
// Define our timeout policy: time out after 2 seconds. We will use the pessimistic timeout strategy, which forces a timeout - even when the underlying delegate doesn't support it.
var timeoutPolicy = Policy
.Timeout(TimeSpan.FromSeconds(2), TimeoutStrategy.Pessimistic,
// This use of onTimeout demonstrates the point about capturing walked-away-from Tasks with TimeoutStrategy.Pessimistic discussed in the Polly wiki, here: https://github.com/App-vNext/Polly/wiki/Timeout#pessimistic-timeout-1
onTimeout: (ctx, span, abandonedTask) =>
{
{
abandonedTask.ContinueWith(t =>
{
// ContinueWith important!: the abandoned task may very well still be executing, when the caller times out on waiting for it!
if (t.IsFaulted)
{
progress.Report(ProgressWithMessage(".The task previously walked-away-from now terminated with exception: " + t.Exception.Message,
Color.Yellow));
}
else if (t.IsCanceled)
{
// (If the executed delegates do not honour cancellation, this IsCanceled branch may never be hit. It can be good practice however to include, in case a Policy configured with TimeoutStrategy.Pessimistic is used to execute a delegate honouring cancellation.)
progress.Report(ProgressWithMessage(".The task previously walked-away-from now was canceled.", Color.Yellow));
}
else
{
// extra logic (if desired) for tasks which complete, despite the caller having 'walked away' earlier due to timeout.
progress.Report(ProgressWithMessage(".The task previously walked-away-from now eventually completed.", Color.Yellow));
}
});
}
}
);
// Define our waitAndRetry policy: keep retrying with 4 second gaps. This is (intentionally) too long: to demonstrate that the timeout policy will time out on this before waiting for the retry.
RetryPolicy waitAndRetryPolicy = Policy
.Handle <Exception>()
.WaitAndRetryForever(
attempt => TimeSpan.FromSeconds(4),
(exception, calculatedWaitDuration) =>
{
progress.Report(ProgressWithMessage(".Log,then retry: " + exception.Message, Color.Yellow));
retries++;
});
// Define a fallback policy: provide a nice substitute message to the user, if we found the call was rejected due to the timeout policy.
FallbackPolicy <String> fallbackForTimeout = Policy <String>
.Handle <TimeoutRejectedException>()
.Fallback(
fallbackValue: /* Demonstrates fallback value syntax */ "Please try again later [Fallback for timeout]",
onFallback: b =>
{
watch.Stop();
progress.Report(ProgressWithMessage("Fallback catches failed with: " + b.Exception.Message + " (after " + watch.ElapsedMilliseconds + "ms)", Color.Red));
eventualFailuresDueToTimeout++;
}
);
// Define a fallback policy: provide a substitute string to the user, for any exception.
FallbackPolicy <String> fallbackForAnyException = Policy <String>
.Handle <Exception>()
.Fallback(
fallbackAction: /* Demonstrates fallback action/func syntax */ () => { return("Please try again later [Fallback for any exception]"); },
onFallback: e =>
{
watch.Stop();
progress.Report(ProgressWithMessage("Fallback catches eventually failed with: " + e.Exception.Message + " (after " + watch.ElapsedMilliseconds + "ms)", Color.Red));
eventualFailuresForOtherReasons++;
}
);
// Compared to previous demo08: here we use *instance* wrap syntax, to wrap all in one go.
PolicyWrap <String> policyWrap = fallbackForAnyException.Wrap(fallbackForTimeout).Wrap(timeoutPolicy).Wrap(waitAndRetryPolicy);
using (var client = new WebClient())
{
bool internalCancel = false;
totalRequests = 0;
while (!internalCancel && !cancellationToken.IsCancellationRequested)
{
totalRequests++;
watch = new Stopwatch();
watch.Start();
try
{
// Manage the call according to the whole policy wrap.
string response = policyWrap.Execute(ct => client.DownloadString(Configuration.WEB_API_ROOT + "/api/values/" + totalRequests), cancellationToken);
watch.Stop();
progress.Report(ProgressWithMessage("Response: " + response + "(after " + watch.ElapsedMilliseconds + "ms)", Color.Green));
eventualSuccesses++;
}
catch (Exception e) // try-catch not needed, now that we have a Fallback.Handle<Exception>. It's only been left in to *demonstrate* it should never get hit.
{
throw new InvalidOperationException("Should never arrive here. Use of fallbackForAnyException should have provided nice fallback value for any exceptions.", e);
}
// Wait half second
Thread.Sleep(500);
internalCancel = TerminateDemosByKeyPress && Console.KeyAvailable;
}
}
}
private async Task <FaceDetectResult[]> MakeFaceDetectRequest(byte[] imageBytes, string apiKey, Guid requestId, PolicyWrap <HttpResponseMessage> policy)
{
_log.Info($"Making detect request requestId: {requestId} apiKey:{apiKey} ticks: {DateTime.Now.Ticks}");
string strResult = string.Empty;
FaceDetectResult[] result = null;
// Request parameters.
const string requestParameters = "returnFaceId=true&returnFaceLandmarks=false";
// Get the API URL and the API key from settings.
var uriBase = ConfigurationManager.AppSettings["faceDetectApiUrl"];
// Configure the HttpClient request headers.
_client.DefaultRequestHeaders.Clear();
_client.DefaultRequestHeaders.Accept.Clear();
_client.DefaultRequestHeaders.Add("Ocp-Apim-Subscription-Key", apiKey);
//_client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
// Assemble the URI for the REST API Call.
var uri = uriBase + "?" + requestParameters;
try
{
// Execute the REST API call, implementing our resiliency strategy.
HttpResponseMessage response = await policy.ExecuteAsync(() => _client.PostAsync(uri, FaceHelper.GetImageHttpContent(imageBytes)));
// Get the JSON response.
strResult = await response.Content.ReadAsStringAsync();
result = await response.Content.ReadAsAsync <FaceDetectResult[]>();
_log.Info($"detect completed: {strResult} requestId: {requestId} apiKey:{apiKey} ticks: {DateTime.Now.Ticks}");
}
catch (BrokenCircuitException bce)
{
_log.Error($"Could not contact the Face API service due to the following error: {bce.Message} requestId: {requestId} apiKey:{apiKey} ticks: {DateTime.Now.Ticks}", bce);
}
catch (Exception e)
{
_log.Error($"Critical error-MakeFaceDetectRequest: {e.Message} requestId: {requestId} apiKey:{apiKey} string result:{strResult} ticks: {DateTime.Now.Ticks}", e);
}
return(result);
}
public async Task <FaceDetectResult[]> DetectFaces(byte[] imageBytes, string apiKey, Guid requestId, PolicyWrap <HttpResponseMessage> policy)
{
return(await MakeFaceDetectRequest(imageBytes, apiKey, requestId, policy));
}
public CustomersAPIService(HttpClient client, Policy[] resiliencePolicies)
{
_client = client;
_policy = Policy.WrapAsync(resiliencePolicies);
}
public static IRestResponse ExecuteWithPolicy(this IRestClient client, IRestRequest request, PolicyWrap policy)
{
// capture the exception so we can push it though the standard response flow.
PolicyResult <IRestResponse> val = policy.ExecuteAndCapture(() => client.Execute(request));
IRestResponse restResponse = val.Result;
if (restResponse == null)
{
restResponse = new RestResponse
{
Request = request,
ErrorException = val.FinalException
};
}
return(restResponse);
}
static void Main(string[] args)
{
Console.WriteLine("Hello World!");
Log.Logger = new LoggerConfiguration()
.WriteTo.Console()
.WriteTo.File("log-.txt", rollingInterval: RollingInterval.Day)
.CreateLogger();
_circuitBreakerPolicy = Policy.Handle <HttpRequestException>()
.CircuitBreaker(
// number of exceptions before breaking circuit
5,
// time circuit opened before retry
TimeSpan.FromMinutes(1),
(exception, duration) =>
{
// on circuit opened
Log.Information("Circuit breaker opened");
},
() =>
{
// on circuit closed
Log.Information("Circuit breaker reset");
});
_retryPolicy = Policy.Handle <HttpRequestException>()
.WaitAndRetry(
// number of retries
4,
// exponential backofff
retryAttempt => TimeSpan.FromSeconds(retryAttempt),
// on retry
(exception, timeSpan, retryCount, context) =>
{
var msg = $"Retry {retryCount} implemented with Polly's RetryPolicy " +
$"of {context.PolicyKey} " +
$"at {context.ExecutionKey}";
Log.Warning(msg);
});
// Define a fallback policy: provide a nice substitute message to the user, if we found the circuit was broken.
FallbackPolicy <UserPayload> fallbackForCircuitBreaker = Policy <UserPayload>
.Handle <BrokenCircuitException>()
.Fallback(
fallbackValue: new UserPayload {
Users = null, ErrorMessage = "Please try again later [Fallback for broken circuit]"
},
onFallback: b =>
{
Log.Information("Fallback catches failed with: " + b.Exception.Message, ConsoleColor.Red);
}
);
// Define a fallback policy: provide a substitute string to the user, for any exception.
FallbackPolicy <UserPayload> fallbackForAnyException = Policy <UserPayload>
.Handle <Exception>()
.Fallback(
fallbackAction: /* Demonstrates fallback action/func syntax */ () => { return(new UserPayload {
Users = null, ErrorMessage = "Please try again later [Fallback for any exception]"
}); },
onFallback: e =>
{
Log.Information("Fallback catches failed with: " + e.Exception.Message, ConsoleColor.DarkMagenta);
}
);
PolicyWrap myResilienceStrategy = Policy.Wrap(_retryPolicy, _circuitBreakerPolicy);
PolicyWrap <UserPayload> policyWrap = fallbackForAnyException.Wrap(fallbackForCircuitBreaker.Wrap(myResilienceStrategy));
LoopCalls(policyWrap);
}
public ResilientHttpClient(ILogger logger)
{
this.logger = logger;
policyWrapper = Policy.WrapAsync(CreatePolicies());
}
private async Task <InternalPersonDetails[]> MakeListPersonGroupRequest(string startPerson, string apiKey, string largegroupid, Guid requestId, PolicyWrap <HttpResponseMessage> policy)
{
string strResult = string.Empty;
_log.Info($"Making ListPerson GET request requestId: {requestId} apiKey:{apiKey} start person {startPerson} ticks: {DateTime.Now.Ticks}");
InternalPersonDetails[] result = null;
// Request parameters.
string requestParameters = largegroupid + "/persons";
// Get the API URL and the API key from settings.
var uriBase = ConfigurationManager.AppSettings["facePersonApiUrl"];
// Configure the HttpClient request headers.
_client.DefaultRequestHeaders.Clear();
_client.DefaultRequestHeaders.Accept.Clear();
_client.DefaultRequestHeaders.Add("Ocp-Apim-Subscription-Key", apiKey);
// Assemble the URI for the REST API Call.
var uri = uriBase + "/" + requestParameters;
if (startPerson != string.Empty)
{
uri += "?start=" + startPerson;
}
try
{
// Execute the REST API call, implementing our resiliency strategy.
HttpResponseMessage response = await policy.ExecuteAsync(() => _client.GetAsync(uri));
// Get the JSON response.
strResult = await response.Content.ReadAsStringAsync();
result = await response.Content.ReadAsAsync <InternalPersonDetails[]>();
_log.Info($"ListPersonGroup completed: requestId: {requestId} apiKey:{apiKey} ticks: {DateTime.Now.Ticks}");
}
catch (BrokenCircuitException bce)
{
_log.Error($"Could not contact the Face API service due to the following error: {bce.Message} requestId: {requestId} apiKey:{apiKey} ticks: {DateTime.Now.Ticks}", bce);
}
catch (Exception e)
{
_log.Error($"Critical error-MakeListPersonGroupRequest: {e.Message} requestId: {requestId} apiKey:{apiKey} string result:{strResult} ticks: {DateTime.Now.Ticks}", e);
}
return(result);
}
public ResilientHttpClient(Policy[] policies, ILogger logger)
{
this.logger = logger;
// Add Policies to be applied
policyWrapper = Policy.WrapAsync(policies);
}
public static async Task <bool> RunDetect(Guid requestID, string apis, string name, string source,
Stream incomingPicture, string sourceContainerName, string resultContainerName, IAsyncCollector <object> outputItem, TraceWriter log, string videoName = null)
{
string apikey = string.Empty;
try
{
string[] apiArr = apis.Split(',');
int randomApi = FaceHelper.Instance.Next(0, apiArr.Length);
apikey = apiArr[randomApi];
log.Info($"RunDetect request id: {requestID} apiKey: {apikey} ticks: {DateTime.Now.Ticks}");
Tuple <HttpClient, PolicyWrap <HttpResponseMessage> > tuple = FaceHelper.HttpClientList.GetOrAdd(apikey, new Tuple <HttpClient, PolicyWrap <HttpResponseMessage> >(
new HttpClient(),
FaceHelper.DefineAndRetrieveResiliencyStrategy(log)));
HttpClient client = tuple.Item1;
PolicyWrap <HttpResponseMessage> policy = tuple.Item2;
IDatabase cache = FaceHelper.Connection.GetDatabase(int.Parse(FaceHelper.Connection.GetDatabase(1).StringGet(apikey)));
//the large group id it's based on the mac address we get - each MAC address can work with different face api group
string largegroupid = ConfigurationManager.AppSettings[source];
if (videoName == null)
{
log.Info($"Detecting {name} requestId: {requestID} apiKey: {apikey} ticks: {DateTime.Now.Ticks}");
}
else
{
log.Info($"Detecting thumbnail {name} from {videoName} requestId: {requestID} apiKey: {apikey} ticks: {DateTime.Now.Ticks}");
}
byte[] pictureImage;
// Convert the incoming image stream to a byte array.
using (var br = new BinaryReader(incomingPicture))
{
pictureImage = br.ReadBytes((int)incomingPicture.Length);
}
var detectionResult = await new FaceDetect(log, client).DetectFaces(pictureImage, apikey, requestID, policy);
if ((detectionResult != null) && (detectionResult.Length > 0))
{
//prepare identify request
int maxCandidate = int.Parse(ConfigurationManager.AppSettings["maxNumOfCandidatesReturned"]);
double threshold = double.Parse(ConfigurationManager.AppSettings["confidenceThreshold"]);
var identifyResquest = new FaceIdentifyRequest()
{
ConfidenceThreshold = threshold,
MaxNumOfCandidatesReturned = maxCandidate,
LargePersonGroupId = largegroupid,
FaceIds = detectionResult.Select(s => s.FaceId).ToArray()
};
var identifyResult = await new FaceIdentify(log, client).IdentifyFaces(identifyResquest, apikey, requestID, policy);
if ((identifyResult == null) || (identifyResult.Length == 0))
{
log.Info($"No identification result requestId: {requestID}, apiKey:{apikey} ticks: {DateTime.Now.Ticks}");
}
var personResult = new PersonDetails(log, client);
//merging results and find person name
for (int i = 0; i < detectionResult.Length; i++)
{
if (videoName == null)
{
detectionResult[i].FaceBlobName = string.Concat(detectionResult[i].FaceId, "_", name);
}
else
{
detectionResult[i].FaceBlobName = videoName + "/" + name;
}
if ((identifyResult != null) && (identifyResult.Length > 0))
{
detectionResult[i].Candidates = identifyResult[i].Candidates;
for (int j = 0; j < detectionResult[i].Candidates.Length; j++)
{
string personid = detectionResult[i].Candidates[j].PersonId.ToString();
string personName = cache.StringGet(largegroupid + "-" + personid);
if (string.IsNullOrEmpty(personName) == true)
{
log.Info($"Missing cache requestId: {requestID} apiKey: {apikey} personId: {personid} ticks: {DateTime.Now.Ticks}");
var tPerson = await personResult.GetPersonName(personid, apikey, largegroupid, requestID, policy);
personName = tPerson.Name;
cache.StringSet(largegroupid + "-" + personid, personName, null, When.Always);
}
detectionResult[i].Candidates[j].PersonName = new InternalPersonDetails()
{
PersonId = detectionResult[i].Candidates[j].PersonId,
Name = personName
};
}
}
}
}
else
{
log.Info($"No dectection result requestId: {requestID}, apiKey:{apikey} ticks: {DateTime.Now.Ticks}");
//in case of video, we want to create a link to the face detected by AMS (Azure Media Services) although face api didn't recognize it
if (videoName != null)
{
detectionResult = new FaceDetectResult[1] {
new FaceDetectResult()
{
FaceBlobName = videoName + "/" + name
}
}
}
;
}
string blobname = videoName ?? name;
var actionResult = new FaceIdentifyResult()
{
BlobName = blobname,
ContainerName = sourceContainerName,
ResultContainerName = resultContainerName,
BlobLength = incomingPicture.Length,
CreatedDateTime = DateTime.UtcNow,
RequestId = requestID,
ApiKey = apikey,
LargeGroupId = largegroupid,
Source = source,
DetectResultList = detectionResult
};
string strResult = JsonConvert.SerializeObject(actionResult);
await outputItem.AddAsync(strResult);
}
catch (Exception ex)
{
log.Error($"Exception Message: {ex.Message}, requestId: {requestID}, apiKey:{apikey} ticks: {DateTime.Now.Ticks}", ex);
return(false);
}
return(true);
}
public PollyServiceClient()
{
_client = new HttpClient();
_gatewayUri = _primaryUri;
var circuitBreakerPolicy = Policy
.Handle <Exception>()
.CircuitBreakerAsync(
exceptionsAllowedBeforeBreaking: 4,
durationOfBreak: TimeSpan.FromSeconds(3),
onBreak: (ex, breakDelay) =>
{
//Called when circuit first open
//Setting the backupUri so calls now go to backup gateway
_gatewayUri = _backupUri;
},
onReset: () =>
{
//Called when circuit is closed again.
//Primary gateway is responding again, setting to primaryUri.
_gatewayUri = _primaryUri;
},
onHalfOpen: () =>
{
//Called when the policy is going to check the original call to see if there are no exceptions.
//Send the call to the primary gateway to see if it's operational again.
_gatewayUri = _primaryUri;;
}
);
var waitAndRetryPolicy = Policy
.Handle <Exception>(e => !(e is BrokenCircuitException)) // Exception filtering! We don't retry if the inner circuit-breaker judges the underlying system is out of commission!
.WaitAndRetryForeverAsync(
attempt => TimeSpan.FromMilliseconds(200),
(exception, calculatedWaitDuration) =>
{
//Handle the exception here.
});
FallbackPolicy <String> fallbackForCircuitBreaker = Policy <String>
.Handle <BrokenCircuitException>()
.FallbackAsync(
fallbackAction: /* Demonstrates fallback action/func syntax */ async ct =>
{
await Task.FromResult(true);
//This is called after the circuit breaker is tripped
//and the gatewayUri is changed to point to the backup
//gateway. This call runs on the backup gateway.
return(await ClientWrapper());
},
onFallbackAsync: async e =>
{
await Task.FromResult(true);
}
);
//Something really bad has happened.
FallbackPolicy <String> fallbackForAnyException = Policy <String>
.Handle <Exception>()
.FallbackAsync(
fallbackAction: /* Demonstrates fallback action/func syntax */ async ct =>
{
await Task.FromResult(true);
return("Another exception occurred.");
},
onFallbackAsync: async e =>
{
await Task.FromResult(true);
}
);
PolicyWrap myResilienceStrategy = Policy.Wrap(waitAndRetryPolicy, circuitBreakerPolicy);
_policyWrap = fallbackForAnyException.WrapAsync(fallbackForCircuitBreaker.WrapAsync(myResilienceStrategy));
}
public override async Task ExecuteAsync(CancellationToken cancellationToken, IProgress <DemoProgress> progress)
{
if (cancellationToken == null)
{
throw new ArgumentNullException(nameof(cancellationToken));
}
if (progress == null)
{
throw new ArgumentNullException(nameof(progress));
}
// Let's call a web api service to make repeated requests to a server.
// The service is programmed to fail after 3 requests in 5 seconds.
eventualSuccesses = 0;
retries = 0;
eventualFailuresDueToCircuitBreaking = 0;
eventualFailuresForOtherReasons = 0;
progress.Report(ProgressWithMessage(typeof(AsyncDemo08_Wrap_Fallback_WaitAndRetry_CircuitBreaker).Name));
progress.Report(ProgressWithMessage("======"));
progress.Report(ProgressWithMessage(String.Empty));
Stopwatch watch = null;
// Define our waitAndRetry policy: keep retrying with 200ms gaps.
var waitAndRetryPolicy = Policy
.Handle <Exception>(e => !(e is BrokenCircuitException)) // Exception filtering! We don't retry if the inner circuit-breaker judges the underlying system is out of commission!
.WaitAndRetryForeverAsync(
attempt => TimeSpan.FromMilliseconds(200),
(exception, calculatedWaitDuration) =>
{
progress.Report(ProgressWithMessage(".Log,then retry: " + exception.Message, Color.Yellow));
retries++;
});
// Define our CircuitBreaker policy: Break if the action fails 4 times in a row.
var circuitBreakerPolicy = Policy
.Handle <Exception>()
.CircuitBreakerAsync(
exceptionsAllowedBeforeBreaking: 4,
durationOfBreak: TimeSpan.FromSeconds(3),
onBreak: (ex, breakDelay) =>
{
progress.Report(ProgressWithMessage(".Breaker logging: Breaking the circuit for " + breakDelay.TotalMilliseconds + "ms!", Color.Magenta));
progress.Report(ProgressWithMessage("..due to: " + ex.Message, Color.Magenta));
},
onReset: () => progress.Report(ProgressWithMessage(".Breaker logging: Call ok! Closed the circuit again!", Color.Magenta)),
onHalfOpen: () => progress.Report(ProgressWithMessage(".Breaker logging: Half-open: Next call is a trial!", Color.Magenta))
);
// Define a fallback policy: provide a nice substitute message to the user, if we found the circuit was broken.
FallbackPolicy <String> fallbackForCircuitBreaker = Policy <String>
.Handle <BrokenCircuitException>()
.FallbackAsync(
fallbackValue: /* Demonstrates fallback value syntax */ "Please try again later [message substituted by fallback policy]",
onFallbackAsync: async b =>
{
await Task.FromResult(true);
watch.Stop();
progress.Report(ProgressWithMessage("Fallback catches failed with: " + b.Exception.Message
+ " (after " + watch.ElapsedMilliseconds + "ms)", Color.Red));
eventualFailuresDueToCircuitBreaking++;
}
);
// Define a fallback policy: provide a substitute string to the user, for any exception.
FallbackPolicy <String> fallbackForAnyException = Policy <String>
.Handle <Exception>()
.FallbackAsync(
fallbackAction: /* Demonstrates fallback action/func syntax */ async ct =>
{
await Task.FromResult(true);
/* do something else async if desired */
return("Please try again later [Fallback for any exception]");
},
onFallbackAsync: async e =>
{
await Task.FromResult(true);
watch.Stop();
progress.Report(ProgressWithMessage("Fallback catches eventually failed with: " + e.Exception.Message
+ " (after " + watch.ElapsedMilliseconds + "ms)", Color.Red));
eventualFailuresForOtherReasons++;
}
);
// As demo07: we combine the waitAndRetryPolicy and circuitBreakerPolicy into a PolicyWrap, using the *static* Policy.Wrap syntax.
PolicyWrap myResilienceStrategy = Policy.WrapAsync(waitAndRetryPolicy, circuitBreakerPolicy);
// Added in demo08: we wrap the two fallback policies onto the front of the existing wrap too. Demonstrates the *instance* wrap syntax. And the fact that the PolicyWrap myResilienceStrategy from above is just another Policy, which can be onward-wrapped too.
// With this pattern, you can build an overall resilience strategy programmatically, reusing some common parts (eg PolicyWrap myResilienceStrategy) but varying other parts (eg Fallback) individually for different calls.
PolicyWrap <String> policyWrap = fallbackForAnyException.WrapAsync(fallbackForCircuitBreaker.WrapAsync(myResilienceStrategy));
// For info: Equivalent to: PolicyWrap<String> policyWrap = Policy.WrapAsync(fallbackForAnyException, fallbackForCircuitBreaker, waitAndRetryPolicy, circuitBreakerPolicy);
totalRequests = 0;
using (var client = new HttpClient())
{
bool internalCancel = false;
// Do the following until a key is pressed
while (!internalCancel && !cancellationToken.IsCancellationRequested)
{
totalRequests++;
watch = new Stopwatch();
watch.Start();
try
{
// Manage the call according to the whole policy wrap
string response = await policyWrap.ExecuteAsync(ct =>
client.GetStringAsync(Configuration.WEB_API_ROOT + "/api/values/" + totalRequests), cancellationToken);
watch.Stop();
// Display the response message on the console
progress.Report(ProgressWithMessage("Response : " + response + " (after " + watch.ElapsedMilliseconds + "ms)", Color.Green));
eventualSuccesses++;
}
catch (Exception e) // try-catch not needed, now that we have a Fallback.Handle<Exception>. It's only been left in to *demonstrate* it should never get hit.
{
throw new InvalidOperationException("Should never arrive here. Use of fallbackForAnyException should have provided nice fallback value for any exceptions.", e);
}
// Wait half second
await Task.Delay(TimeSpan.FromSeconds(0.5), cancellationToken);
internalCancel = TerminateDemosByKeyPress && Console.KeyAvailable;
}
}
}
/// <summary>
/// Initializes a new instance of the <see cref="T:EasyCaching.HybridCache.HybridCachingProvider"/> class.
/// </summary>
/// <param name="name">Name.</param>
/// <param name="optionsAccs">Options accs.</param>
/// <param name="factory">Providers factory</param>
/// <param name="bus">Bus.</param>
/// <param name="loggerFactory">Logger factory.</param>
public HybridCachingProvider(
string name
, HybridCachingOptions optionsAccs
, IEasyCachingProviderFactory factory
, IEasyCachingBus bus = null
, ILoggerFactory loggerFactory = null
)
{
ArgumentCheck.NotNull(factory, nameof(factory));
this._name = name;
this._options = optionsAccs;
ArgumentCheck.NotNullOrWhiteSpace(_options.TopicName, nameof(_options.TopicName));
this._logger = loggerFactory?.CreateLogger <HybridCachingProvider>();
// Here use the order to distinguish traditional provider
var local = factory.GetCachingProvider(_options.LocalCacheProviderName);
if (local.IsDistributedCache)
{
throw new NotFoundCachingProviderException("Can not found any local caching providers.");
}
else
{
this._localCache = local;
}
// Here use the order to distinguish traditional provider
var distributed = factory.GetCachingProvider(_options.DistributedCacheProviderName);
if (!distributed.IsDistributedCache)
{
throw new NotFoundCachingProviderException("Can not found any distributed caching providers.");
}
else
{
this._distributedCache = distributed;
}
this._bus = bus ?? NullEasyCachingBus.Instance;
this._bus.Subscribe(_options.TopicName, OnMessage);
this._cacheId = Guid.NewGuid().ToString("N");
// policy
retryAsyncPolicy = Policy.Handle <Exception>()
.WaitAndRetryAsync(this._options.BusRetryCount, retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt - 1)));
retryPolicy = Policy.Handle <Exception>()
.WaitAndRetry(this._options.BusRetryCount, retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt - 1)));
fallbackPolicy = Policy.Handle <Exception>().Fallback(() => { });
fallbackAsyncPolicy = Policy.Handle <Exception>().FallbackAsync(ct =>
{
return(Task.CompletedTask);
});
_busSyncWrap = Policy.Wrap(fallbackPolicy, retryPolicy);
_busAsyncWrap = Policy.WrapAsync(fallbackAsyncPolicy, retryAsyncPolicy);
}
public static void Execute()
{
Console.WriteLine(MethodBase.GetCurrentMethod().DeclaringType.Name);
Console.WriteLine("=======");
// Let's call a web api service to make repeated requests to a server.
// The service is programmed to fail after 3 requests in 5 seconds.
var client = new WebClient();
int eventualSuccesses = 0;
int retries = 0;
int eventualFailuresDueToCircuitBreaking = 0;
int eventualFailuresForOtherReasons = 0;
Stopwatch watch = null;
// Define our waitAndRetry policy: keep retrying with 200ms gaps.
RetryPolicy waitAndRetryPolicy = Policy
.Handle <Exception>(e => !(e is BrokenCircuitException)) // Exception filtering! We don't retry if the inner circuit-breaker judges the underlying system is out of commission!
.WaitAndRetryForever(
attempt => TimeSpan.FromMilliseconds(200),
(exception, calculatedWaitDuration) =>
{
ConsoleHelper.WriteLineInColor(".Log,then retry: " + exception.Message, ConsoleColor.Yellow);
retries++;
});
// Define our CircuitBreaker policy: Break if the action fails 4 times in a row.
CircuitBreakerPolicy circuitBreakerPolicy = Policy
.Handle <Exception>()
.CircuitBreaker(
exceptionsAllowedBeforeBreaking: 4,
durationOfBreak: TimeSpan.FromSeconds(3),
onBreak: (ex, breakDelay) =>
{
ConsoleHelper.WriteLineInColor(".Breaker logging: Breaking the circuit for " + breakDelay.TotalMilliseconds + "ms!", ConsoleColor.Magenta);
ConsoleHelper.WriteLineInColor("..due to: " + ex.Message, ConsoleColor.Magenta);
},
onReset: () => ConsoleHelper.WriteLineInColor(".Breaker logging: Call ok! Closed the circuit again!", ConsoleColor.Magenta),
onHalfOpen: () => ConsoleHelper.WriteLineInColor(".Breaker logging: Half-open: Next call is a trial!", ConsoleColor.Magenta)
);
// Define a fallback policy: provide a nice substitute message to the user, if we found the circuit was broken.
FallbackPolicy <String> fallbackForCircuitBreaker = Policy <String>
.Handle <BrokenCircuitException>()
.Fallback(
fallbackValue: /* Demonstrates fallback value syntax */ "Please try again later [Fallback for broken circuit]",
onFallback: b =>
{
watch.Stop();
ConsoleHelper.WriteInColor("Fallback catches failed with: " + b.Exception.Message, ConsoleColor.Red);
ConsoleHelper.WriteLineInColor(" (after " + watch.ElapsedMilliseconds + "ms)", ConsoleColor.Red);
eventualFailuresDueToCircuitBreaking++;
}
);
// Define a fallback policy: provide a substitute string to the user, for any exception.
FallbackPolicy <String> fallbackForAnyException = Policy <String>
.Handle <Exception>()
.Fallback(
fallbackAction: /* Demonstrates fallback action/func syntax */ () => { return("Please try again later [Fallback for any exception]"); },
onFallback: e =>
{
watch.Stop();
ConsoleHelper.WriteInColor("Fallback catches eventually failed with: " + e.Exception.Message, ConsoleColor.Red);
ConsoleHelper.WriteLineInColor(" (after " + watch.ElapsedMilliseconds + "ms)", ConsoleColor.Red);
eventualFailuresForOtherReasons++;
}
);
// As demo07: we combine the waitAndRetryPolicy and circuitBreakerPolicy into a PolicyWrap, using the *static* Policy.Wrap syntax.
PolicyWrap myResilienceStrategy = Policy.Wrap(waitAndRetryPolicy, circuitBreakerPolicy);
// Added in demo08: we wrap the two fallback policies onto the front of the existing wrap too. Demonstrates the *instance* wrap syntax. And the fact that the PolicyWrap myResilienceStrategy from above is just another Policy, which can be onward-wrapped too.
// With this pattern, you can build an overall resilience strategy programmatically, reusing some common parts (eg PolicyWrap myResilienceStrategy) but varying other parts (eg Fallback) individually for different calls.
PolicyWrap <String> policyWrap = fallbackForAnyException.Wrap(fallbackForCircuitBreaker.Wrap(myResilienceStrategy));
// For info: Equivalent to: PolicyWrap<String> policyWrap = Policy.Wrap(fallbackForAnyException, fallbackForCircuitBreaker, waitAndRetryPolicy, circuitBreakerPolicy);
int i = 0;
// Do the following until a key is pressed
while (!Console.KeyAvailable)
{
i++;
watch = new Stopwatch();
watch.Start();
try
{
// Manage the call according to the whole policy wrap.
string msg = policyWrap.Execute(() => client.DownloadString(Configuration.WEB_API_ROOT + "/api/values/" + i));
watch.Stop();
// Display the response message on the console
ConsoleHelper.WriteInColor("Response : " + msg, ConsoleColor.Green);
ConsoleHelper.WriteLineInColor(" (after " + watch.ElapsedMilliseconds + "ms)", ConsoleColor.Green);
eventualSuccesses++;
}
catch (Exception e) // try-catch not needed, now that we have a Fallback.Handle<Exception>. It's only been left in to *demonstrate* it should never get hit.
{
throw new InvalidOperationException("Should never arrive here. Use of fallbackForAnyException should have provided nice fallback value for any exceptions.", e);
}
// Wait half second
Thread.Sleep(500);
}
Console.WriteLine("");
Console.WriteLine("Total requests made : " + i);
Console.WriteLine("Requests which eventually succeeded : " + eventualSuccesses);
Console.WriteLine("Retries made to help achieve success : " + retries);
Console.WriteLine("Requests failed early by broken circuit : " + eventualFailuresDueToCircuitBreaking);
Console.WriteLine("Requests which failed after longer delay: " + eventualFailuresForOtherReasons);
}
public async Task <InternalPersonDetails> GetPersonName(string personId, string apiKey, string largegroupid, Guid requestId, PolicyWrap <HttpResponseMessage> policy)
{
return(await MakePersonNameRequest(personId, apiKey, largegroupid, requestId, policy));
}
public static void Execute()
{
Console.WriteLine(MethodBase.GetCurrentMethod().DeclaringType.Name);
Console.WriteLine("=======");
// Let's call a web api service to make repeated requests to a server.
// The service is programmed to fail after 3 requests in 5 seconds.
var client = new WebClient();
int eventualSuccesses = 0;
int retries = 0;
int eventualFailuresDueToCircuitBreaking = 0;
int eventualFailuresForOtherReasons = 0;
// define wait and retry policy
var waitAndRetryPolicy = Policy.Handle <Exception>(e => !(e is BrokenCircuitException)) // Exception filtering. We don't retry if the inner circuit-breaker judges the underlying system is out of commission!
.WaitAndRetryForever(
sleepDurationProvider: attempt => TimeSpan.FromMilliseconds(200), // wait 200ms between each try
onRetry: (exception, calculatedWaitDuration) =>
{
// this is the new exception handler
ConsoleHelper.WriteLineInColor("[" + DateTime.Now.ToString("hh:mm:ss.fff") + "]" + ".Log,then retry: " + exception.Message, ConsoleColor.Yellow);
retries++;
});
// define circuit breaker policy. Break if the action fails 4 times in a row
var circuitBreakerPolicy = Policy.Handle <Exception>().CircuitBreaker(
exceptionsAllowedBeforeBreaking: 4,
durationOfBreak: TimeSpan.FromSeconds(3),
onBreak: (ex, breakDelay) =>
{
ConsoleHelper.WriteLineInColor("[" + DateTime.Now.ToString("hh:mm:ss.fff") + "]" + ".Breaker logging: Breaking the circuit for " + breakDelay.TotalMilliseconds + " ms!", ConsoleColor.Magenta);
ConsoleHelper.WriteLineInColor("[" + DateTime.Now.ToString("hh:mm:ss") + "]" + "..due to: " + ex.Message, ConsoleColor.Magenta);
},
onReset: () => ConsoleHelper.WriteLineInColor("[" + DateTime.Now.ToString("hh:mm:ss.fff") + "]" + ".Breaker logging: Call ok! Closed the circuit again!", ConsoleColor.Magenta),
onHalfOpen: () => ConsoleHelper.WriteLineInColor("[" + DateTime.Now.ToString("hh:mm:ss.fff") + "]" + ".Breaker logging: Half-open: Next call is a trial!", ConsoleColor.Magenta)
);
PolicyWrap policyWrap = Policy.Wrap(waitAndRetryPolicy, circuitBreakerPolicy);
int i = 0;
// Do the following until a key is pressed
while (!Console.KeyAvailable)
{
i++;
Stopwatch watch = new Stopwatch();
watch.Start();
try
{
// Retry the following call according to the policy wrap
string msg = policyWrap.Execute <String>(() =>
{
return(client.DownloadString(Configuration.WEB_API_ROOT + "/api/values/" + i));
});
watch.Stop();
// Display the response message on the console
ConsoleHelper.WriteLineInColor("[" + DateTime.Now.ToString("hh:mm:ss.fff") + "]" + "Response : " + msg, ConsoleColor.Green);
ConsoleHelper.WriteLineInColor("[" + DateTime.Now.ToString("hh:mm:ss.fff") + "]" + " (after " + watch.ElapsedMilliseconds + "ms)", ConsoleColor.Green);
eventualSuccesses++;
}
catch (BrokenCircuitException b)
{
watch.Stop();
ConsoleHelper.WriteInColor("[" + DateTime.Now.ToString("hh:mm:ss.fff") + "]" + "Request " + i + " failed with: " + b.GetType().Name, ConsoleColor.Red);
ConsoleHelper.WriteLineInColor(" (after " + watch.ElapsedMilliseconds + "ms)", ConsoleColor.Red);
eventualFailuresDueToCircuitBreaking++;
}
catch (Exception e)
{
watch.Stop();
ConsoleHelper.WriteLineInColor("[" + DateTime.Now.ToString("hh:mm:ss.fff") + "]" + "Request " + i + " eventually failed with: " + e.Message, ConsoleColor.Red);
ConsoleHelper.WriteLineInColor(" (after " + watch.ElapsedMilliseconds + "ms)", ConsoleColor.Red);
eventualFailuresForOtherReasons++;
}
// Wait half second
Thread.Sleep(500);
}
Console.WriteLine("");
Console.WriteLine("Total requests made : " + i);
Console.WriteLine("Requests which eventually succeeded : " + eventualSuccesses);
Console.WriteLine("Retries made to help achieve success: " + retries);
Console.WriteLine("Requests failed early by broken circuit : " + eventualFailuresDueToCircuitBreaking);
Console.WriteLine("Requests which failed after longer delay: " + eventualFailuresForOtherReasons);
}
public override async Task ExecuteAsync(CancellationToken cancellationToken, IProgress <DemoProgress> progress)
{
if (cancellationToken == null)
{
throw new ArgumentNullException(nameof(cancellationToken));
}
if (progress == null)
{
throw new ArgumentNullException(nameof(progress));
}
// Let's call a web api service to make repeated requests to a server.
// The service is programmed to fail after 3 requests in 5 seconds.
eventualSuccesses = 0;
retries = 0;
eventualFailuresDueToCircuitBreaking = 0;
eventualFailuresForOtherReasons = 0;
progress.Report(ProgressWithMessage(typeof(AsyncDemo07_WaitAndRetryNestingCircuitBreakerUsingPolicyWrap).Name));
progress.Report(ProgressWithMessage("======"));
progress.Report(ProgressWithMessage(String.Empty));
// Define our waitAndRetry policy: keep retrying with 200ms gaps.
var waitAndRetryPolicy = Policy
.Handle <Exception>(e => !(e is BrokenCircuitException)) // Exception filtering! We don't retry if the inner circuit-breaker judges the underlying system is out of commission!
.WaitAndRetryForeverAsync(
attempt => TimeSpan.FromMilliseconds(200),
(exception, calculatedWaitDuration) =>
{
// This is your new exception handler!
// Tell the user what they've won!
progress.Report(ProgressWithMessage(".Log,then retry: " + exception.Message, Color.Yellow));
retries++;
});
// Define our CircuitBreaker policy: Break if the action fails 4 times in a row.
var circuitBreakerPolicy = Policy
.Handle <Exception>()
.CircuitBreakerAsync(
exceptionsAllowedBeforeBreaking: 4,
durationOfBreak: TimeSpan.FromSeconds(3),
onBreak: (ex, breakDelay) =>
{
progress.Report(ProgressWithMessage(".Breaker logging: Breaking the circuit for " + breakDelay.TotalMilliseconds + "ms!", Color.Magenta));
progress.Report(ProgressWithMessage("..due to: " + ex.Message, Color.Magenta));
},
onReset: () => progress.Report(ProgressWithMessage(".Breaker logging: Call ok! Closed the circuit again!", Color.Magenta)),
onHalfOpen: () => progress.Report(ProgressWithMessage(".Breaker logging: Half-open: Next call is a trial!", Color.Magenta))
);
// New for demo07: combine the waitAndRetryPolicy and circuitBreakerPolicy into a PolicyWrap.
PolicyWrap policyWrap = Policy.WrapAsync(waitAndRetryPolicy, circuitBreakerPolicy);
using (var client = new HttpClient())
{
totalRequests = 0;
bool internalCancel = false;
// Do the following until a key is pressed
while (!internalCancel && !cancellationToken.IsCancellationRequested)
{
totalRequests++;
Stopwatch watch = new Stopwatch();
watch.Start();
try
{
// Retry the following call according to the policy wrap
string response = await policyWrap.ExecuteAsync <String>(ct =>
{
// This code is executed through both policies in the wrap: WaitAndRetry outer, then CircuitBreaker inner. Demo 06 shows a broken-out version of what this is equivalent to.
return(client.GetStringAsync(Configuration.WEB_API_ROOT + "/api/values/" + totalRequests));
}, cancellationToken);
watch.Stop();
// Display the response message on the console
progress.Report(ProgressWithMessage("Response : " + response
+ " (after " + watch.ElapsedMilliseconds + "ms)", Color.Green));
eventualSuccesses++;
}
catch (BrokenCircuitException b)
{
watch.Stop();
progress.Report(ProgressWithMessage("Request " + totalRequests + " failed with: " + b.GetType().Name
+ " (after " + watch.ElapsedMilliseconds + "ms)", Color.Red));
eventualFailuresDueToCircuitBreaking++;
}
catch (Exception e)
{
watch.Stop();
progress.Report(ProgressWithMessage("Request " + totalRequests + " eventually failed with: " + e.Message
+ " (after " + watch.ElapsedMilliseconds + "ms)", Color.Red));
eventualFailuresForOtherReasons++;
}
// Wait half second
await Task.Delay(TimeSpan.FromSeconds(0.5), cancellationToken);
internalCancel = TerminateDemosByKeyPress && Console.KeyAvailable;
}
}
}
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
services.AddOptions();
services.AddApiVersioning(
o =>
{
o.AssumeDefaultVersionWhenUnspecified = true;
o.DefaultApiVersion = new ApiVersion(1, 0);
});
var azureStorageSettings = GetSettings <AzureStorageSettings>();
var notificationServiceSettings = GetSettings <NotificationServiceSettings>();
var faultToleranceSettings = GetSettings <FaultToleranceSettings>();
services.AddSingleton <IMetricsClient>(context =>
{
var metricsClientFactory = new MetricsClientFactory(context.GetRequiredService <ILoggerFactory>(),
TimeSpan.FromSeconds(15));
return(metricsClientFactory.CreateMetricsClient <LoggerMetricsClient>());
});
TimeoutPolicy timeoutPolicy = Policy.Timeout(faultToleranceSettings.TimeoutLength, TimeoutStrategy.Pessimistic);
CircuitBreakerPolicy circuitBreakerPolicy = Policy
.Handle <Exception>()
.CircuitBreaker(
exceptionsAllowedBeforeBreaking: faultToleranceSettings.ExceptionsAllowedBeforeBreaking,
durationOfBreak: TimeSpan.FromMinutes(faultToleranceSettings.DurationOfBreakInMinutes)
);
PolicyWrap policyWrap = Policy.Wrap(circuitBreakerPolicy, timeoutPolicy);
services.AddSingleton <ISyncPolicy>(policyWrap);
QueueClient queueClient = new QueueClient(notificationServiceSettings.ServiceBusConnectionString,
notificationServiceSettings.QueueName);
ServiceBusNotificationServiceClient notificationService = new ServiceBusNotificationServiceClient(queueClient);
services.AddSingleton <INotificationService>(context =>
new NotificationServiceMetricsDecorator(
new NotificationServiceFaultToleranceDecorator(
notificationService,
context.GetRequiredService <ISyncPolicy>()),
context.GetRequiredService <IMetricsClient>()));
AzureCloudTable profileCloudTable = new AzureCloudTable(azureStorageSettings.ConnectionString, azureStorageSettings.ProfilesTableName);
AzureTableProfileStore profileStore = new AzureTableProfileStore(profileCloudTable);
services.AddSingleton <IProfileStore>(context =>
new ProfileStoreMetricsDecorator(
new ProfileStoreFaultToleranceDecorator(
profileStore,
context.GetRequiredService <ISyncPolicy>()),
context.GetRequiredService <IMetricsClient>()));
AzureCloudTable messagesCloudTable = new AzureCloudTable(azureStorageSettings.ConnectionString, azureStorageSettings.MessagesTableName);
AzureTableMessagesStore messagesStore = new AzureTableMessagesStore(messagesCloudTable);
services.AddSingleton <IMessagesStore>(context =>
new MessagesStoreMetricsDecorator(
new MessagesStoreFaultToleranceDecorator(
messagesStore,
context.GetRequiredService <ISyncPolicy>()),
context.GetRequiredService <IMetricsClient>()));
AzureCloudTable conversationsCloudTable = new AzureCloudTable(azureStorageSettings.ConnectionString, azureStorageSettings.UsersTableName);
AzureTableConversationsStore conversationsStore = new AzureTableConversationsStore(conversationsCloudTable, messagesStore);
services.AddSingleton <IConversationsStore>(context =>
new ConversationStoreMetricsDecorator(
new ConversationsStoreFaultToleranceDecorator(
conversationsStore,
context.GetRequiredService <ISyncPolicy>()),
context.GetRequiredService <IMetricsClient>()));
services.AddSingleton <IConversationService>(context =>
new ConversationServiceMetricsDecorator(
new ConversationService(
context.GetRequiredService <IConversationsStore>(),
context.GetRequiredService <ILogger <ConversationService> >(),
context.GetRequiredService <INotificationService>()),
context.GetRequiredService <IMetricsClient>()));
services.AddLogging();
services.AddMvc();
}
public static void Execute()
{
Console.WriteLine(MethodBase.GetCurrentMethod().DeclaringType.Name);
Console.WriteLine("=======");
// Let's call a web api service to make repeated requests to a server.
// The service is programmed to fail after 3 requests in 5 seconds.
var client = new WebClient();
int eventualSuccesses = 0;
int retries = 0;
int eventualFailuresDueToTimeout = 0;
int eventualFailuresForOtherReasons = 0;
Stopwatch watch = null;
// Define our timeout policy: time out after 2 seconds. We will use the pessimistic timeout strategy, which forces a timeout - even when the underlying delegate doesn't support it.
var timeoutPolicy = Policy
.Timeout(TimeSpan.FromSeconds(2), TimeoutStrategy.Pessimistic);
// Define our waitAndRetry policy: keep retrying with 4 second gaps. This is (intentionally) too long: to demonstrate that the timeout policy will time out on this before waiting for the retry.
RetryPolicy waitAndRetryPolicy = Policy
.Handle <Exception>()
.WaitAndRetryForever(
attempt => TimeSpan.FromSeconds(4),
(exception, calculatedWaitDuration) =>
{
ConsoleHelper.WriteLineInColor(".Log,then retry: " + exception.Message, ConsoleColor.Yellow);
retries++;
});
// Define a fallback policy: provide a nice substitute message to the user, if we found the call was rejected due to the timeout policy.
FallbackPolicy <String> fallbackForTimeout = Policy <String>
.Handle <TimeoutRejectedException>()
.Fallback(
fallbackValue: /* Demonstrates fallback value syntax */ "Please try again later [Fallback for timeout]",
onFallback: b =>
{
watch.Stop();
ConsoleHelper.WriteInColor("Fallback catches failed with: " + b.Exception.Message, ConsoleColor.Red);
ConsoleHelper.WriteLineInColor(" (after " + watch.ElapsedMilliseconds + "ms)", ConsoleColor.Red);
eventualFailuresDueToTimeout++;
}
);
// Define a fallback policy: provide a substitute string to the user, for any exception.
FallbackPolicy <String> fallbackForAnyException = Policy <String>
.Handle <Exception>()
.Fallback(
fallbackAction: /* Demonstrates fallback action/func syntax */ () => { return("Please try again later [Fallback for any exception]"); },
onFallback: e =>
{
watch.Stop();
ConsoleHelper.WriteInColor("Fallback catches eventually failed with: " + e.Exception.Message, ConsoleColor.Red);
ConsoleHelper.WriteLineInColor(" (after " + watch.ElapsedMilliseconds + "ms)", ConsoleColor.Red);
eventualFailuresForOtherReasons++;
}
);
// Compared to previous demo08: here we use *instance* wrap syntax, to wrap all in one go.
PolicyWrap <String> policyWrap = fallbackForAnyException.Wrap(fallbackForTimeout).Wrap(timeoutPolicy).Wrap(waitAndRetryPolicy).Wrap(waitAndRetryPolicy);
int i = 0;
while (!Console.KeyAvailable)
{
i++;
watch = new Stopwatch();
watch.Start();
try
{
// Manage the call according to the whole policy wrap.
string msg = policyWrap.Execute(() => client.DownloadString(Configuration.WEB_API_ROOT + "/api/values/" + i));
watch.Stop();
// Display the response message on the console
ConsoleHelper.WriteInColor("Response : " + msg, ConsoleColor.Green);
ConsoleHelper.WriteLineInColor(" (after " + watch.ElapsedMilliseconds + "ms)", ConsoleColor.Green);
eventualSuccesses++;
}
catch (Exception e) // try-catch not needed, now that we have a Fallback.Handle<Exception>. It's only been left in to *demonstrate* it should never get hit.
{
throw new InvalidOperationException("Should never arrive here. Use of fallbackForAnyException should have provided nice fallback value for any exceptions.", e);
}
// Wait half second
Thread.Sleep(500);
}
Console.WriteLine("");
Console.WriteLine("Total requests made : " + i);
Console.WriteLine("Requests which eventually succeeded : " + eventualSuccesses);
Console.WriteLine("Retries made to help achieve success : " + retries);
Console.WriteLine("Requests timed out by timeout policy : " + eventualFailuresDueToTimeout);
Console.WriteLine("Requests which failed after longer delay: " + eventualFailuresForOtherReasons);
}
