Skip to main content

ASP.NET Core 1.1 –Error in Response Caching Middleware

After putting a first version of our ASP.NET Core application into acceptance, we got a strange bug back.

Sometimes after a cold start, users mentioned that the dropdown lists inside the application were empty. The application is using the Response Caching middleware to prevent having to fetch those lists over and over again from the database.

When looking at the server logs, we found the following error message:

exception": "System.ArgumentException: An item with the same key has already been added. Key: \r\n at System.ThrowHelper.ThrowAddingDuplicateWithKeyArgumentException(Object key)\r\n at System.Collections.Generic.Dictionary2.Insert(TKey key, TValue value, Boolean add)\r\n at System.Collections.Generic.Dictionary2.Add(TKey key, TValue value)\r\n at Microsoft.AspNetCore.Server.Kestrel.Internal.Http.FrameResponseHeaders.AddValueFast(String key, StringValues value)\r\n at Microsoft.AspNetCore.Server.Kestrel.Internal.Http.FrameHeaders.System.Collections.Generic.IDictionary<System.String,Microsoft.Extensions.Primitives.StringValues>.Add(String key, StringValues value)\r\n at Microsoft.AspNetCore.Server.Kestrel.Internal.Http.FrameHeaders.System.Collections.Generic.ICollection<System.Collections.Generic.KeyValuePair<System.String,Microsoft.Extensions.Primitives.StringValues>>.Add(KeyValuePair2 item)\r\n at Microsoft.AspNetCore.ResponseCaching.ResponseCachingMiddleware.d__10.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter1.GetResult()\r\n at Microsoft.AspNetCore.ResponseCaching.ResponseCachingMiddleware.d__11.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---

Seems there is a bug in the Response Caching Middleware, the response caching middleware is causing an exception when it tries to add the same header. This is a bug that should be fixed in  the ASP.NET Core 1.1.1 patch.

Labels:

Popular posts from this blog

Podman– Command execution failed with exit code 125

After updating WSL on one of the developer machines, Podman failed to work. When we took a look through Podman Desktop, we noticed that Podman had stopped running and returned the following error message: Error: Command execution failed with exit code 125 Here are the steps we tried to fix the issue: We started by running podman info to get some extra details on what could be wrong: >podman info OS: windows/amd64 provider: wsl version: 5.3.1 Cannot connect to Podman. Please verify your connection to the Linux system using `podman system connection list`, or try `podman machine init` and `podman machine start` to manage a new Linux VM Error: unable to connect to Podman socket: failed to connect: dial tcp 127.0.0.1:2655: connectex: No connection could be made because the target machine actively refused it. That makes sense as the podman VM was not running. Let’s check the VM: >podman machine list NAME         ...
Read more

Cache stampede: when our cache turned against us

While investigating some performance issues, we ran into an ASP.NET Core API that cached a fairly expensive aggregation query for 60 seconds. Under normal load, that was fine: one request rebuilds the cache, everyone else reads from it. Under peak load, dozens of requests would arrive in that same expiry window, all see a cache miss, and all fire the same expensive query in parallel. The database didn't like that. That was the moment when our caching layer stopped helping and started hurting. A burst of requests comes in at the same time, all miss the cache, and all go hammer the database or the downstream API at once. That's a cache stampede . The cache was supposed to protect our backend, and for a few hundred milliseconds it did the opposite. Why this happens IMemoryCache.GetOrCreate (and its async sibling) looks like it protects you, but it doesn't add any locking on its own. Look at the naive version: public async Task<Report> GetReportAsync(string key) ...
Read more

Azure DevOps/ GitHub emoji

I’m really bad at remembering emoji’s. So here is cheat sheet with all emoji’s that can be used in tools that support the github emoji markdown markup: All credits go to rcaviers who created this list.
Read more