internal static void UpdateCachedResponse(CacheKey cacheKey,
HttpResponseMessage cachedResponse,
HttpResponseMessage serverResponse,
ICacheStore store)
{
TraceWriter.WriteLine("CachingHandler.UpdateCachedResponse - response: " + serverResponse.Headers,
TraceLevel.Verbose);
// update only if server had a cachecontrol.
// TODO: merge CacheControl headers instead of replace
if ((serverResponse.Headers.CacheControl != null) && !serverResponse.Headers.CacheControl.NoCache)
// added to cover issue #139
{
TraceWriter.WriteLine(
"CachingHandler.UpdateCachedResponse - CacheControl: " + serverResponse.Headers.CacheControl,
TraceLevel.Verbose);
cachedResponse.Headers.CacheControl = serverResponse.Headers.CacheControl;
}
else
{
TraceWriter.WriteLine(
"CachingHandler.UpdateCachedResponse - CacheControl missing from server. Applying sliding expiration. Date => " +
DateTimeOffset.UtcNow, TraceLevel.Verbose);
}
cachedResponse.Headers.Date = DateTimeOffset.UtcNow; // very important
store.AddOrUpdate(cacheKey, cachedResponse);
}
private void Trace(string message)
{
if (string.IsNullOrEmpty(message))
{
return;
}
TraceWriter?.WriteLine(message);
}
private static void CheckForCacheCowHeader(HttpResponseMessage responseMessage)
{
var header = responseMessage.Headers.GetCacheCowHeader();
if (header != null)
{
TraceWriter.WriteLine("!!WARNING!! response stored with CacheCowHeader!!", TraceLevel.Warning);
}
}
public Task<HttpResponseMessage> DeserializeToResponseAsync(Stream stream)
{
var response = new HttpResponseMessage();
response.Content = new StreamContent(stream);
response.Content.Headers.Add("Content-Type", "application/http;msgtype=response");
TraceWriter.WriteLine("before ReadAsHttpResponseMessageAsync",
TraceLevel.Verbose);
return response.Content.ReadAsHttpResponseMessageAsync();
}
public static HttpResponseMessage AddCacheCowHeader(this HttpResponseMessage response,
CacheCowHeader header)
{
var previousCacheCowHeader = response.Headers.GetCacheCowHeader();
if (previousCacheCowHeader != null)
{
TraceWriter.WriteLine("WARNING: Already had this header: {0} NOw setting this: {1}", TraceLevel.Warning, previousCacheCowHeader, header);
response.Headers.Remove(CacheCowHeader.Name);
}
response.Headers.Add(CacheCowHeader.Name, header.ToString());
return(response);
}
public void AddOrUpdate(CacheKey key, HttpResponseMessage response)
{
var fileName = key.EnsureFolderAndGetFileName(_dataRoot);
if (File.Exists(fileName))
{
TraceWriter.WriteLine("Must remove file", TraceLevel.Verbose);
TryRemove(key);
}
var ms = new MemoryStream();
_serializer.SerializeAsync(TaskHelpers.FromResult(response), ms).Wait();
ms.Position = 0;
using (var fs = GetFile(fileName, FileMode.Create))
{
TraceWriter.WriteLine("Before serialise", TraceLevel.Verbose);
ms.CopyTo(fs);
TraceWriter.WriteLine("After serialise", TraceLevel.Verbose);
}
var info = new FileInfo(fileName);
// Update database
_database.Cache
.Insert(new CacheItem
{
Domain = key.Domain,
Hash = Convert.ToBase64String(key.Hash),
LastAccessed = DateTime.Now,
LastUpdated = (response.Content != null) && response.Content.Headers.LastModified.HasValue
? response.Content.Headers.LastModified.Value.UtcDateTime
: DateTime.Now
,
Size = info.Length
});
TraceWriter.WriteLine("After db update", TraceLevel.Verbose);
// tell quota manager
_quotaManager.ItemAdded(new CacheItemMetadata
{
Domain = key.Domain,
Key = key.Hash,
LastAccessed = DateTime.Now,
Size = info.Length
});
}
public async Task <HttpResponseMessage> DeserializeToResponseAsync(Stream stream)
{
var response = new HttpResponseMessage();
response.Content = new StreamContent(stream);
response.Content.Headers.Add("Content-Type", "application/http;msgtype=response");
TraceWriter.WriteLine("before ReadAsHttpResponseMessageAsync",
TraceLevel.Verbose);
var responseMessage = await response.Content.ReadAsHttpResponseMessageAsync();
if (responseMessage.Content != null && _bufferContent)
{
await responseMessage.Content.LoadIntoBufferAsync();
}
return(responseMessage);
}
internal static void UpdateCachedResponse(CacheKey cacheKey,
HttpResponseMessage cachedResponse,
HttpResponseMessage serverResponse,
ICacheStore store)
{
TraceWriter.WriteLine("CachingHandler.UpdateCachedResponse - response: " + serverResponse.Headers.ToString(), TraceLevel.Verbose);
// update only if server had a cachecontrol.
// TODO: merge CacheControl headers instead of replace
if (serverResponse.Headers.CacheControl != null && (!serverResponse.Headers.CacheControl.NoCache)) // added to cover issue #139
{
TraceWriter.WriteLine("CachingHandler.UpdateCachedResponse - CacheControl: " + serverResponse.Headers.CacheControl.ToString(), TraceLevel.Verbose);
cachedResponse.Headers.CacheControl = serverResponse.Headers.CacheControl;
cachedResponse.Headers.Date = DateTimeOffset.UtcNow; // very important
store.AddOrUpdate(cacheKey, cachedResponse);
}
}
public Task SerializeAsync(Task<HttpResponseMessage> response, Stream stream)
{
return response.Then(r =>
{
if (r.Content != null)
{
TraceWriter.WriteLine("SerializeAsync - before load",
TraceLevel.Verbose);
return r.Content.LoadIntoBufferAsync()
.Then(() =>
{
TraceWriter.WriteLine("SerializeAsync - after load", TraceLevel.Verbose);
var httpMessageContent = new HttpMessageContent(r);
// All in-memory and CPU-bound so no need to async
return httpMessageContent.ReadAsByteArrayAsync();
})
.Then(buffer =>
{
TraceWriter.WriteLine("SerializeAsync - after ReadAsByteArrayAsync", TraceLevel.Verbose);
return Task.Factory.FromAsync(stream.BeginWrite, stream.EndWrite,
buffer, 0, buffer.Length, null, TaskCreationOptions.AttachedToParent);
}
);
;
}
else
{
TraceWriter.WriteLine("Content NULL - before load",
TraceLevel.Verbose);
var httpMessageContent = new HttpMessageContent(r);
// All in-memory and CPU-bound so no need to async
var buffer = httpMessageContent.ReadAsByteArrayAsync().Result;
return Task.Factory.FromAsync(stream.BeginWrite, stream.EndWrite,
buffer, 0, buffer.Length, null, TaskCreationOptions.AttachedToParent);
}
}
);
}
private bool TryRemove(CacheItemMetadata metadata, bool tellQuotaManager)
{
var fileName = metadata.EnsureFolderAndGetFileName(_dataRoot);
if (File.Exists(fileName))
{
File.Delete(fileName);
TraceWriter.WriteLine("After delete file {0}", TraceLevel.Verbose, fileName);
_database.Cache.DeleteByHash(Convert.ToBase64String(metadata.Key));
TraceWriter.WriteLine("After db update. File name: {0}", TraceLevel.Verbose, fileName);
if (tellQuotaManager)
{
_quotaManager.ItemRemoved(metadata);
}
return(true);
}
return(false);
}
public bool TryGetValue(CacheKey key, out HttpResponseMessage response)
{
response = null;
string fileName = key.EnsureFolderAndGetFileName(_dataRoot);
if (File.Exists(fileName))
{
var ms = new MemoryStream();
using (var fs = GetFile(fileName, FileMode.Open))
{
TraceWriter.WriteLine("TryGetValue - before DeserializeToResponseAsync", TraceLevel.Verbose);
fs.CopyTo(ms);
ms.Position = 0;
}
response = _serializer.DeserializeToResponseAsync(ms).Result;
TraceWriter.WriteLine("TryGetValue - After DeserializeToResponseAsync", TraceLevel.Verbose);
if (response.Content != null)
{
var task = response.Content.LoadIntoBufferAsync();
task.Wait();
TraceWriter.WriteLine("TryGetValue - After wait", TraceLevel.Verbose);
}
_database.Cache
.UpdateByHash(new
{
Hash = Convert.ToBase64String(key.Hash),
LastAccessed = DateTime.Now
});
TraceWriter.WriteLine("After updating Last Accessed", TraceLevel.Verbose);
}
return(response != null);
}
internal async static Task UpdateCachedResponseAsync(CacheKey cacheKey,
HttpResponseMessage cachedResponse,
HttpResponseMessage serverResponse,
ICacheStore store)
{
TraceWriter.WriteLine("CachingHandler.UpdateCachedResponseAsync - response: " + serverResponse.Headers.ToString(), TraceLevel.Verbose);
// update only if server had a cachecontrol.
// TODO: merge CacheControl headers instead of replace
if (serverResponse.Headers.CacheControl != null && (!serverResponse.Headers.CacheControl.NoCache)) // added to cover issue #139
{
TraceWriter.WriteLine("CachingHandler.UpdateCachedResponseAsync - CacheControl: " + serverResponse.Headers.CacheControl.ToString(), TraceLevel.Verbose);
cachedResponse.Headers.CacheControl = serverResponse.Headers.CacheControl;
}
else
{
TraceWriter.WriteLine("CachingHandler.UpdateCachedResponseAsync - CacheControl missing from server. Applying sliding expiration. Date => " + DateTimeOffset.UtcNow, TraceLevel.Verbose);
}
cachedResponse.Headers.Date = DateTimeOffset.UtcNow; // very important
CheckForCacheCowHeader(cachedResponse);
await store.AddOrUpdateAsync(cacheKey, cachedResponse);
}
public async Task SerializeAsync(HttpResponseMessage response, Stream stream)
{
if (response.Content != null)
{
TraceWriter.WriteLine("SerializeAsync - before load",
TraceLevel.Verbose);
if (_bufferContent)
{
await response.Content.LoadIntoBufferAsync();
}
TraceWriter.WriteLine("SerializeAsync - after load", TraceLevel.Verbose);
}
else
{
TraceWriter.WriteLine("Content NULL - before load",
TraceLevel.Verbose);
}
var httpMessageContent = new HttpMessageContent(response);
var buffer = await httpMessageContent.ReadAsByteArrayAsync();
TraceWriter.WriteLine("SerializeAsync - after ReadAsByteArrayAsync", TraceLevel.Verbose);
stream.Write(buffer, 0, buffer.Length);
}
private void TraceLine(object o)
{
WriteIndentation();
TraceWriter.WriteLine(o);
}
protected void TraceInformation(string message)
{
TraceWriter.WriteLine(message);
}
protected void TraceInformation(string format, params object[] args)
{
TraceWriter.WriteLine(format, args);
}
public CachingHandler(ICacheStore cacheStore, IVaryHeaderStore varyHeaderStore)
{
_cacheStore = cacheStore;
UseConditionalPutPatchDelete = true;
MustRevalidateByDefault = true;
VaryHeaderStore = varyHeaderStore;
DefaultVaryHeaders = new string[] { "Accept" };
ResponseValidator = (response) =>
{
// 13.4
//Unless specifically constrained by a cache-control (section 14.9) directive, a caching system MAY always store
// a successful response (see section 13.8) as a cache entry, MAY return it without validation if it
// is fresh, and MAY return it after successful validation. If there is neither a cache validator nor an
// explicit expiration time associated with a response, we do not expect it to be cached, but certain caches MAY violate this expectation
// (for example, when little or no network connectivity is available).
// 14.9.1
// If the no-cache directive does not specify a field-name, then a cache MUST NOT use the response to satisfy a subsequent request without
// successful revalidation with the origin server. This allows an origin server to prevent caching
// even by caches that have been configured to return stale responses to client requests.
//If the no-cache directive does specify one or more field-names, then a cache MAY use the response
// to satisfy a subsequent request, subject to any other restrictions on caching. However, the specified
// field-name(s) MUST NOT be sent in the response to a subsequent request without successful revalidation
// with the origin server. This allows an origin server to prevent the re-use of certain header fields in a response, while still allowing caching of the rest of the response.
if (!response.StatusCode.IsIn(_cacheableStatuses))
{
return(ResponseValidationResult.NotCacheable);
}
if (!response.IsSuccessStatusCode || response.Headers.CacheControl == null ||
response.Headers.CacheControl.NoStore) // || response.Headers.CacheControl.NoCache was removed. See issue
{
return(ResponseValidationResult.NotCacheable);
}
if (response.Headers.Date == null)
{
TraceWriter.WriteLine("Response date is NULL", TraceLevel.Warning);
}
response.Headers.Date = response.Headers.Date ?? DateTimeOffset.UtcNow; // this also helps in cache creation
var dateTimeOffset = response.Headers.Date;
TraceWriter.WriteLine(
String.Format("CachedResponse date was => {0} - compared to UTC.Now => {1}", dateTimeOffset, DateTimeOffset.UtcNow), TraceLevel.Verbose);
if (response.Content == null)
{
return(ResponseValidationResult.NotCacheable);
}
if (response.Headers.CacheControl.MaxAge == null &&
response.Headers.CacheControl.SharedMaxAge == null &&
response.Content.Headers.Expires == null)
{
return(ResponseValidationResult.NotCacheable);
}
if (response.Headers.CacheControl.NoCache)
{
return(ResponseValidationResult.MustRevalidate);
}
// here we use
if (response.Content.Headers.Expires != null &&
response.Content.Headers.Expires < DateTimeOffset.UtcNow)
{
return(response.Headers.CacheControl.ShouldRevalidate(MustRevalidateByDefault)
? ResponseValidationResult.MustRevalidate : ResponseValidationResult.Stale);
}
if (response.Headers.CacheControl.MaxAge != null &&
DateTimeOffset.UtcNow > response.Headers.Date.Value.Add(response.Headers.CacheControl.MaxAge.Value))
{
return(response.Headers.CacheControl.ShouldRevalidate(MustRevalidateByDefault)
? ResponseValidationResult.MustRevalidate : ResponseValidationResult.Stale);
}
if (response.Headers.CacheControl.SharedMaxAge != null &&
DateTimeOffset.UtcNow > response.Headers.Date.Value.Add(response.Headers.CacheControl.SharedMaxAge.Value))
{
return(response.Headers.CacheControl.ShouldRevalidate(MustRevalidateByDefault)
? ResponseValidationResult.MustRevalidate : ResponseValidationResult.Stale);
}
return(ResponseValidationResult.OK);
};
_ignoreRequestRules = (request) =>
{
if (request.Method.IsCacheIgnorable())
{
return(true);
}
// client can tell CachingHandler not to do caching for a particular request
if (request.Headers.CacheControl != null)
{
if (request.Headers.CacheControl.NoStore)
{
return(true);
}
}
return(false);
};
ResponseStoragePreparationRules = (response) =>
{
// 14.9.3
// If a response includes both an Expires header and a max-age directive,
// the max-age directive overrides the Expires header, even if the Expires header is more restrictive.
if (response.Content.Headers.Expires != null &&
(response.Headers.CacheControl.MaxAge != null || response.Headers.CacheControl.SharedMaxAge != null))
{
response.Content.Headers.Expires = null;
}
};
}
// TODO: this method is terribly long. Shorten
protected async override Task <HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
var cacheCowHeader = new CacheCowHeader();
string uri = request.RequestUri.ToString();
TraceWriter.WriteLine("{0} - Starting SendAsync", TraceLevel.Verbose, request.RequestUri.ToString());
// check if needs to be ignored
if (_ignoreRequestRules(request))
{
return(await base.SendAsync(request, cancellationToken)); // EXIT !! _________________
}
IEnumerable <string> varyHeaders;
if (!VaryHeaderStore.TryGetValue(uri, out varyHeaders))
{
varyHeaders = DefaultVaryHeaders;
}
var cacheKey = new CacheKey(uri,
request.Headers.Where(x => varyHeaders.Any(y => y.Equals(x.Key,
StringComparison.CurrentCultureIgnoreCase)))
.SelectMany(z => z.Value)
);
// get from cache and verify response
HttpResponseMessage cachedResponse;
ResponseValidationResult validationResultForCachedResponse = ResponseValidationResult.NotExist;
TraceWriter.WriteLine("{0} - Before TryGetValue", TraceLevel.Verbose, request.RequestUri.ToString());
cachedResponse = await _cacheStore.GetValueAsync(cacheKey);
cacheCowHeader.DidNotExist = cachedResponse == null;
TraceWriter.WriteLine("{0} - After TryGetValue: DidNotExist => {1}", TraceLevel.Verbose, request.RequestUri.ToString(), cacheCowHeader.DidNotExist);
if (!cacheCowHeader.DidNotExist.Value) // so if it EXISTS in cache
{
TraceWriter.WriteLine("{0} - Existed in the cache. CacheControl Headers => {1}", TraceLevel.Verbose, request.RequestUri.ToString(),
cachedResponse.Headers.CacheControl.ToString());
cachedResponse.RequestMessage = request;
validationResultForCachedResponse = ResponseValidator(cachedResponse);
}
TraceWriter.WriteLine("{0} - After ResponseValidator => {1}",
TraceLevel.Verbose, request.RequestUri, validationResultForCachedResponse);
// PUT/PATCH/DELETE validation
if (request.Method.IsPutPatchOrDelete() && validationResultForCachedResponse.IsIn(
ResponseValidationResult.OK, ResponseValidationResult.MustRevalidate))
{
ApplyPutPatchDeleteValidationHeaders(request, cacheCowHeader, cachedResponse);
return(await base.SendAsync(request, cancellationToken)); // EXIT !! _____________________________
}
// here onward is only GET only. See if cache OK and if it is then return
if (validationResultForCachedResponse == ResponseValidationResult.OK)
{
cacheCowHeader.RetrievedFromCache = true;
return(cachedResponse.AddCacheCowHeader(cacheCowHeader)); // EXIT !! ____________________________
}
// if stale
else if (validationResultForCachedResponse == ResponseValidationResult.Stale)
{
cacheCowHeader.WasStale = true;
var isFreshOrStaleAcceptable = IsFreshOrStaleAcceptable(cachedResponse, request);
if (isFreshOrStaleAcceptable.HasValue && isFreshOrStaleAcceptable.Value) // similar to OK
{
// TODO: CONSUME AND RELEASE Response !!!
return(cachedResponse.AddCacheCowHeader(cacheCowHeader));
// EXIT !! ____________________________
}
else
{
validationResultForCachedResponse = ResponseValidationResult.MustRevalidate; // revalidate
}
}
// cache validation for GET
else if (validationResultForCachedResponse == ResponseValidationResult.MustRevalidate)
{
ApplyGetCacheValidationHeaders(request, cacheCowHeader, cachedResponse);
}
// _______________________________ RESPONSE only GET ___________________________________________
var serverResponse = await base.SendAsync(request, cancellationToken);
// HERE IS LATE FOR APPLYING EXCEPTION POLICY !!!
TraceWriter.WriteLine("{0} - After getting response",
TraceLevel.Verbose, request.RequestUri.ToString());
if (request.Method != HttpMethod.Get) // only interested here if it is a GET - this line really never called - only GET gets here
{
return(serverResponse);
}
// in case of MustRevalidate with result 304
if (validationResultForCachedResponse == ResponseValidationResult.MustRevalidate &&
serverResponse.StatusCode == HttpStatusCode.NotModified)
{
TraceWriter.WriteLine("{0} - Got 304 from the server and ResponseValidationResult.MustRevalidate",
TraceLevel.Verbose, request.RequestUri.ToString());
cachedResponse.RequestMessage = request;
cacheCowHeader.RetrievedFromCache = true;
TraceWriter.WriteLine("{0} - NotModified",
TraceLevel.Verbose, request.RequestUri.ToString());
await UpdateCachedResponseAsync(cacheKey, cachedResponse, serverResponse, _cacheStore);
ConsumeAndDisposeResponse(serverResponse);
return(cachedResponse.AddCacheCowHeader(cacheCowHeader).CopyOtherCacheCowHeaders(serverResponse)); // EXIT !! _______________
}
var validationResult = ResponseValidator(serverResponse);
switch (validationResult)
{
case ResponseValidationResult.MustRevalidate:
case ResponseValidationResult.OK:
TraceWriter.WriteLine("{0} - ResponseValidationResult.OK or MustRevalidate",
TraceLevel.Verbose, request.RequestUri.ToString());
// prepare
ResponseStoragePreparationRules(serverResponse);
// re-create cacheKey with real server accept
// if there is a vary header, store it
if (serverResponse.Headers.Vary != null)
{
varyHeaders = serverResponse.Headers.Vary.Select(x => x).ToArray();
IEnumerable <string> temp;
if (!VaryHeaderStore.TryGetValue(uri, out temp))
{
VaryHeaderStore.AddOrUpdate(uri, varyHeaders);
}
}
// create real cacheKey with correct Vary headers
cacheKey = new CacheKey(uri,
request.Headers.Where(x => varyHeaders.Any(y => y.Equals(x.Key,
StringComparison.CurrentCultureIgnoreCase)))
.SelectMany(z => z.Value)
);
// store the cache
CheckForCacheCowHeader(serverResponse);
await _cacheStore.AddOrUpdateAsync(cacheKey, serverResponse);
TraceWriter.WriteLine("{0} - After AddOrUpdate", TraceLevel.Verbose, request.RequestUri.ToString());
break;
default:
TraceWriter.WriteLine("{0} - ResponseValidationResult. Other",
TraceLevel.Verbose, request.RequestUri.ToString());
TraceWriter.WriteLine("{0} - Before TryRemove", TraceLevel.Verbose, request.RequestUri.ToString());
await _cacheStore.TryRemoveAsync(cacheKey);
TraceWriter.WriteLine("{0} - After TryRemoveAsync", TraceLevel.Verbose, request.RequestUri.ToString());
cacheCowHeader.NotCacheable = true;
break;
}
TraceWriter.WriteLine("{0} - Before returning response",
TraceLevel.Verbose, request.RequestUri.ToString());
return(serverResponse.AddCacheCowHeader(cacheCowHeader));
}
protected void TraceError(string message)
{
HasError = true;
TraceWriter.WriteLine(message);
}
// TODO: this method is terribly long. Shorten
protected override Task <HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
var cacheCowHeader = new CacheCowHeader();
string uri = request.RequestUri.ToString();
TraceWriter.WriteLine("{0} - Starting", TraceLevel.Verbose, request.RequestUri.ToString());
// check if needs to be ignored
if (_ignoreRequestRules(request))
{
return(base.SendAsync(request, cancellationToken)); // EXIT !! _________________
}
IEnumerable <string> varyHeaders;
if (!VaryHeaderStore.TryGetValue(uri, out varyHeaders))
{
varyHeaders = DefaultVaryHeaders;
}
var cacheKey = new CacheKey(uri,
request.Headers.Where(x => varyHeaders.Any(y => y.Equals(x.Key,
StringComparison.CurrentCultureIgnoreCase)))
.SelectMany(z => z.Value)
);
// get from cache and verify response
HttpResponseMessage cachedResponse;
ResponseValidationResult validationResultForCachedResponse = ResponseValidationResult.NotExist;
TraceWriter.WriteLine("{0} - Before TryGetValue", TraceLevel.Verbose, request.RequestUri.ToString());
cacheCowHeader.DidNotExist = !_cacheStore.TryGetValue(cacheKey, out cachedResponse);
TraceWriter.WriteLine("{0} - After TryGetValue", TraceLevel.Verbose, request.RequestUri.ToString());
if (!cacheCowHeader.DidNotExist.Value) // so if it EXISTS in cache
{
cachedResponse.RequestMessage = request;
validationResultForCachedResponse = ResponseValidator(cachedResponse);
}
TraceWriter.WriteLine("{0} - After ResponseValidator {1}",
TraceLevel.Verbose, request.RequestUri, validationResultForCachedResponse);
// PUT validation
if (request.Method == HttpMethod.Put && validationResultForCachedResponse.IsIn(
ResponseValidationResult.OK, ResponseValidationResult.MustRevalidate))
{
// add headers for a cache validation. First check ETag since is better
if (UseConditionalPut)
{
cacheCowHeader.CacheValidationApplied = true;
if (cachedResponse.Headers.ETag != null)
{
request.Headers.Add(HttpHeaderNames.IfMatch,
cachedResponse.Headers.ETag.ToString());
}
else if (cachedResponse.Content.Headers.LastModified != null)
{
request.Headers.Add(HttpHeaderNames.IfUnmodifiedSince,
cachedResponse.Content.Headers.LastModified.Value.ToString("r"));
}
}
return(base.SendAsync(request, cancellationToken)); // EXIT !! _____________________________
}
// here onward is only GET only. See if cache OK and if it is then return
if (validationResultForCachedResponse == ResponseValidationResult.OK)
{
cacheCowHeader.RetrievedFromCache = true;
return(TaskHelpers.FromResult(cachedResponse.AddCacheCowHeader(cacheCowHeader))); // EXIT !! ____________________________
}
// if stale
else if (validationResultForCachedResponse == ResponseValidationResult.Stale)
{
cacheCowHeader.WasStale = true;
var isFreshOrStaleAcceptable = IsFreshOrStaleAcceptable(cachedResponse, request);
if (isFreshOrStaleAcceptable.HasValue && isFreshOrStaleAcceptable.Value) // similar to OK
{
// TODO: CONSUME AND RELEASE Response !!!
return(TaskHelpers.FromResult(cachedResponse.AddCacheCowHeader(cacheCowHeader)));
// EXIT !! ____________________________
}
else
{
validationResultForCachedResponse = ResponseValidationResult.MustRevalidate; // revalidate
}
}
// cache validation for GET
else if (validationResultForCachedResponse == ResponseValidationResult.MustRevalidate)
{
cacheCowHeader.CacheValidationApplied = true;
cacheCowHeader.WasStale = true;
// add headers for a cache validation. First check ETag since is better
if (cachedResponse.Headers.ETag != null)
{
request.Headers.Add(HttpHeaderNames.IfNoneMatch,
cachedResponse.Headers.ETag.ToString());
}
else if (cachedResponse.Content.Headers.LastModified != null)
{
request.Headers.Add(HttpHeaderNames.IfModifiedSince,
cachedResponse.Content.Headers.LastModified.Value.ToString("r"));
}
}
// _______________________________ RESPONSE only GET ___________________________________________
return(base.SendAsync(request, cancellationToken)
.ContinueWith(
tt =>
{
var serverResponse = tt.Result;
TraceWriter.WriteLine("{0} - After getting response",
TraceLevel.Verbose, request.RequestUri.ToString());
if (request.Method != HttpMethod.Get) // only interested here if it is a GET - this line really never called - only GET gets here
{
return serverResponse;
}
// in case of MustRevalidate with result 304
if (validationResultForCachedResponse == ResponseValidationResult.MustRevalidate &&
serverResponse.StatusCode == HttpStatusCode.NotModified)
{
cachedResponse.RequestMessage = request;
cacheCowHeader.RetrievedFromCache = true;
TraceWriter.WriteLine("{0} - NotModified",
TraceLevel.Verbose, request.RequestUri.ToString());
ConsumeAndDisposeResponse(serverResponse);
return cachedResponse.AddCacheCowHeader(cacheCowHeader); // EXIT !! _______________
}
var validationResult = ResponseValidator(serverResponse);
switch (validationResult)
{
case ResponseValidationResult.MustRevalidate:
case ResponseValidationResult.OK:
TraceWriter.WriteLine("{0} - ResponseValidationResult.OK or MustRevalidate",
TraceLevel.Verbose, request.RequestUri.ToString());
// prepare
ResponseStoragePreparationRules(serverResponse);
TraceWriter.WriteLine("{0} - Before AddOrUpdate", TraceLevel.Verbose, request.RequestUri.ToString());
// store the cache
_cacheStore.AddOrUpdate(cacheKey, serverResponse);
TraceWriter.WriteLine("{0} - Before AddOrUpdate", TraceLevel.Verbose, request.RequestUri.ToString());
// if there is a vary header, store it
if (serverResponse.Headers.Vary != null)
{
VaryHeaderStore.AddOrUpdate(uri, serverResponse.Headers.Vary.Select(x => x).ToArray());
}
break;
default:
TraceWriter.WriteLine("{0} - ResponseValidationResult. Other",
TraceLevel.Verbose, request.RequestUri.ToString());
TraceWriter.WriteLine("{0} - Before TryRemove", TraceLevel.Verbose, request.RequestUri.ToString());
_cacheStore.TryRemove(cacheKey);
TraceWriter.WriteLine("{0} - After AddOrUpdate", TraceLevel.Verbose, request.RequestUri.ToString());
cacheCowHeader.NotCacheable = true;
break;
}
TraceWriter.WriteLine("{0} - Before returning response",
TraceLevel.Verbose, request.RequestUri.ToString());
return serverResponse.AddCacheCowHeader(cacheCowHeader);
}
));
}
protected void TraceError(string format, params object[] args)
{
HasError = true;
TraceWriter.WriteLine(format, args);
}
// TODO: this method is terribly long. Shorten
protected override Task <HttpResponseMessage> SendAsync(HttpRequestMessage request,
CancellationToken cancellationToken)
{
var cacheCowHeader = new CacheCowHeader();
var uri = request.RequestUri.ToString();
TraceWriter.WriteLine("{0} - Starting SendAsync", TraceLevel.Verbose, request.RequestUri.ToString());
// check if needs to be ignored
if (_ignoreRequestRules(request))
{
return(base.SendAsync(request, cancellationToken)); // EXIT !! _________________
}
IEnumerable <string> varyHeaders;
if (!VaryHeaderStore.TryGetValue(uri, out varyHeaders))
{
varyHeaders = DefaultVaryHeaders;
}
var cacheKey = new CacheKey(uri,
request.Headers.Where(x => varyHeaders.Any(y => y.Equals(x.Key,
StringComparison.CurrentCultureIgnoreCase)))
.SelectMany(z => z.Value)
);
// get from cache and verify response
HttpResponseMessage cachedResponse;
var validationResultForCachedResponse = ResponseValidationResult.NotExist;
try
{
TraceWriter.WriteLine("{0} - Before TryGetValue", TraceLevel.Verbose, request.RequestUri.ToString());
cacheCowHeader.DidNotExist = !_cacheStore.TryGetValue(cacheKey, out cachedResponse);
TraceWriter.WriteLine("{0} - After TryGetValue: DidNotExist => {1}", TraceLevel.Verbose,
request.RequestUri.ToString(), cacheCowHeader.DidNotExist);
if (!cacheCowHeader.DidNotExist.Value) // so if it EXISTS in cache
{
TraceWriter.WriteLine("{0} - Existed in the cache. CacheControl Headers => {1}", TraceLevel.Verbose,
request.RequestUri.ToString(),
cachedResponse.Headers.CacheControl.ToString());
cachedResponse.RequestMessage = request;
validationResultForCachedResponse = ResponseValidator(cachedResponse);
}
TraceWriter.WriteLine("{0} - After ResponseValidator => {1}",
TraceLevel.Verbose, request.RequestUri, validationResultForCachedResponse);
// PUT validation
if ((request.Method == HttpMethod.Put) && validationResultForCachedResponse.IsIn(
ResponseValidationResult.OK, ResponseValidationResult.MustRevalidate))
{
DoPutValidation(request, cacheCowHeader, cachedResponse);
return(base.SendAsync(request, cancellationToken)); // EXIT !! _____________________________
}
// here onward is only GET only. See if cache OK and if it is then return
if (validationResultForCachedResponse == ResponseValidationResult.OK)
{
cacheCowHeader.RetrievedFromCache = true;
return(TaskHelpers.FromResult(cachedResponse.AddCacheCowHeader(cacheCowHeader)));
// EXIT !! ____________________________
}
// if stale
if (validationResultForCachedResponse == ResponseValidationResult.Stale)
{
cacheCowHeader.WasStale = true;
var isFreshOrStaleAcceptable = IsFreshOrStaleAcceptable(cachedResponse, request);
if (isFreshOrStaleAcceptable.HasValue && isFreshOrStaleAcceptable.Value) // similar to OK
{
return(TaskHelpers.FromResult(cachedResponse.AddCacheCowHeader(cacheCowHeader)));
}
validationResultForCachedResponse = ResponseValidationResult.MustRevalidate; // revalidate
}
// cache validation for GET
else if (validationResultForCachedResponse == ResponseValidationResult.MustRevalidate)
{
DoCacheValidationForGet(request, cacheCowHeader, cachedResponse);
}
}
catch (Exception ex)
{
if (ExceptionHandler == null)
{
throw;
}
ExceptionHandler(ex);
Trace.TraceWarning("Exception was swallowed in CacheCow: " + ex);
return(base.SendAsync(request, cancellationToken));
}
// _______________________________ RESPONSE only GET ___________________________________________
return(base.SendAsync(request, cancellationToken)
.ContinueWith(
tt =>
{
// HERE IS LATE FOR APPLYING EXCEPTION POLICY !!!
var serverResponse = tt.Result;
TraceWriter.WriteLine("{0} - After getting response",
TraceLevel.Verbose, request.RequestUri.ToString());
if (request.Method != HttpMethod.Get)
{
// only interested here if it is a GET - this line really never called - only GET gets here
return serverResponse;
}
// in case of MustRevalidate with result 304
if ((validationResultForCachedResponse == ResponseValidationResult.MustRevalidate) &&
(serverResponse.StatusCode == HttpStatusCode.NotModified))
{
TraceWriter.WriteLine(
"{0} - Got 304 from the server and ResponseValidationResult.MustRevalidate",
TraceLevel.Verbose, request.RequestUri.ToString());
cachedResponse.RequestMessage = request;
cacheCowHeader.RetrievedFromCache = true;
TraceWriter.WriteLine("{0} - NotModified",
TraceLevel.Verbose, request.RequestUri.ToString());
UpdateCachedResponse(cacheKey, cachedResponse, serverResponse, _cacheStore);
ConsumeAndDisposeResponse(serverResponse);
return cachedResponse.AddCacheCowHeader(cacheCowHeader); // EXIT !! _______________
}
var validationResult = ResponseValidator(serverResponse);
switch (validationResult)
{
case ResponseValidationResult.MustRevalidate:
case ResponseValidationResult.OK:
TraceWriter.WriteLine("{0} - ResponseValidationResult.OK or MustRevalidate",
TraceLevel.Verbose, request.RequestUri.ToString());
// prepare
ResponseStoragePreparationRules(serverResponse);
TraceWriter.WriteLine("{0} - Before AddOrUpdate", TraceLevel.Verbose,
request.RequestUri.ToString());
// re-create cacheKey with real server accept
// if there is a vary header, store it
if (serverResponse.Headers.Vary != null)
{
varyHeaders = serverResponse.Headers.Vary.Select(x => x).ToArray();
IEnumerable <string> temp;
if (!VaryHeaderStore.TryGetValue(uri, out temp))
{
VaryHeaderStore.AddOrUpdate(uri, varyHeaders);
}
}
// create real cacheKey with correct Vary headers
cacheKey = new CacheKey(uri,
request.Headers.Where(x => varyHeaders.Any(y => y.Equals(x.Key,
StringComparison.CurrentCultureIgnoreCase)))
.SelectMany(z => z.Value)
);
// store the cache
_cacheStore.AddOrUpdate(cacheKey, serverResponse);
TraceWriter.WriteLine("{0} - After AddOrUpdate", TraceLevel.Verbose,
request.RequestUri.ToString());
break;
default:
TraceWriter.WriteLine("{0} - ResponseValidationResult. Other",
TraceLevel.Verbose, request.RequestUri.ToString());
TraceWriter.WriteLine("{0} - Before TryRemove", TraceLevel.Verbose,
request.RequestUri.ToString());
_cacheStore.TryRemove(cacheKey);
TraceWriter.WriteLine("{0} - After AddOrUpdate", TraceLevel.Verbose,
request.RequestUri.ToString());
cacheCowHeader.NotCacheable = true;
break;
}
TraceWriter.WriteLine("{0} - Before returning response",
TraceLevel.Verbose, request.RequestUri.ToString());
return serverResponse.AddCacheCowHeader(cacheCowHeader);
}));
}
