internal async Task <bool> TryServeFromCacheAsync(OutputCacheContext cacheContext, IReadOnlyList <IOutputCachePolicy> policies)
{
CreateCacheKey(cacheContext);
// Locking cache lookups by default
// TODO: should it be part of the cache implementations or can we assume all caches would benefit from it?
// It makes sense for caches that use IO (disk, network) or need to deserialize the state but could also be a global option
var cacheEntry = await _outputCacheEntryDispatcher.ScheduleAsync(cacheContext.CacheKey, (Store : _store, CacheContext : cacheContext), static async (key, state) => await OutputCacheEntryFormatter.GetAsync(key, state.Store, state.CacheContext.HttpContext.RequestAborted));
private async Task InvokeAwaited(HttpContext httpContext, IReadOnlyList <IOutputCachePolicy> policies)
{
var context = new OutputCacheContext {
HttpContext = httpContext
};
// Add IOutputCacheFeature
AddOutputCacheFeature(context);
try
{
foreach (var policy in policies)
{
await policy.CacheRequestAsync(context, httpContext.RequestAborted);
}
// Should we attempt any caching logic?
if (context.EnableOutputCaching)
{
// Can this request be served from cache?
if (context.AllowCacheLookup)
{
if (await TryServeFromCacheAsync(context, policies))
{
return;
}
}
// Should we store the response to this request?
if (context.AllowCacheStorage)
{
// It is also a pre-condition to reponse locking
var executed = false;
if (context.AllowLocking)
{
var cacheEntry = await _requestDispatcher.ScheduleAsync(context.CacheKey, key => ExecuteResponseAsync());
// The current request was processed, nothing more to do
if (executed)
{
return;
}
// If the result was processed by another request, try to serve it from cache entry (no lookup)
if (await TryServeCachedResponseAsync(context, cacheEntry, policies))
{
return;
}
// If the cache entry couldn't be served, continue to processing the request as usual
}
await ExecuteResponseAsync();
async Task <OutputCacheEntry?> ExecuteResponseAsync()
{
// Hook up to listen to the response stream
ShimResponseStream(context);
try
{
await _next(httpContext);
// The next middleware might change the policy
foreach (var policy in policies)
{
await policy.ServeResponseAsync(context, httpContext.RequestAborted);
}
// If there was no response body, check the response headers now. We can cache things like redirects.
StartResponse(context);
// Finalize the cache entry
await FinalizeCacheBodyAsync(context);
executed = true;
}
finally
{
UnshimResponseStream(context);
}
return(context.CachedResponse);
}
return;
}
}
await _next(httpContext);
}
finally
{
RemoveOutputCacheFeature(httpContext);
}
}
