public static async Task ExecuteAsync(CancellationToken cancellationToken)
{
Console.WriteLine(typeof(AsyncDemo03_WaitAndRetryNTimes_WithEnoughRetries).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 eventualFailures = 0;
// Define our policy:
var policy = Policy.Handle <Exception>().WaitAndRetryAsync(
retryCount: 15, // Retry up to 15 times! - should be enough that we eventually succeed.
sleepDurationProvider: attempt => TimeSpan.FromMilliseconds(200), // Wait 200ms between each try.
onRetry: (exception, calculatedWaitDuration) => // Capture some info for logging!
{
// This is your new exception handler!
// Tell the user what they've won!
ConsoleHelper.WriteLineInColor("Policy logging: " + exception.Message, ConsoleColor.Yellow);
retries++;
});
int i = 0;
// Do the following until a key is pressed
while (!Console.KeyAvailable && !cancellationToken.IsCancellationRequested)
{
i++;
try
{
// Retry the following call according to the policy - 15 times.
await policy.ExecuteAsync(async token =>
{
// This code is executed within the Policy
// Make a request and get a response
string msg = await client.GetStringAsync(Configuration.WEB_API_ROOT + "/api/values/" + i);
// Display the response message on the console
ConsoleHelper.WriteLineInColor("Response : " + msg, ConsoleColor.Green);
eventualSuccesses++;
}, cancellationToken);
}
catch (Exception e)
{
ConsoleHelper.WriteLineInColor("Request " + i + " eventually failed with: " + e.Message, ConsoleColor.Red);
eventualFailures++;
}
// Wait half second before the next request.
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 which eventually failed : " + eventualFailures);
}
public static async Task Execute(CancellationToken cancellationToken)
{
Console.WriteLine(typeof(AsyncDemo06_WaitAndRetryNestingCircuitBreaker).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)
);
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 - 3 times.
await waitAndRetryPolicy.ExecuteAsync(async token =>
{
// This code is executed within the waitAndRetryPolicy
string msg = await circuitBreakerPolicy.ExecuteAsync <String>(() => // Note how we can also Execute() a Func<TResult> and pass back the value.
{
// This code is executed within the circuitBreakerPolicy
// Make a request and get a response
return(client.GetStringAsync(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++;
}, cancellationToken);
}
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);
}