ArgumentException while OutputCache is cached

[abratv]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

Hi,

I got error message in log while i swear my endpoint output is cached
Any how I can find what the cause of this exception?

Moved from StackExchange/StackExchange.Redis#2732

Expected Behavior

• No exception at all
• A way to debug the exception? log the key for example
• Or simply warn, this key is null instead of throwing exception

Steps To Reproduce

• The code is nothing fancy
  It is based on example https://learn.microsoft.com/en-us/aspnet/core/performance/caching/output?view=aspnetcore-8.0
• New custom policy
• VaryByQuery *
• VarByHeader Authorization
• I removed part where if there is Authorization, do not cache (which mean I do need to cache authorized request)
• I used yarp

Exceptions (if any)

System.ArgumentException: A null value is not valid in this context
at StackExchange.Redis.RedisValue.AssertNotNull() in //src/StackExchange.Redis/RedisValue.cs:line 308
at StackExchange.Redis.RedisDatabase.ScriptEvalMessage..ctor(Int32 db, CommandFlags flags, RedisCommand command, String script, Byte[] hexHash, RedisKey[] keys, RedisValue[] values) in //src/StackExchange.Redis/RedisDatabase.cs:line 4814
at StackExchange.Redis.RedisDatabase.ScriptEvalMessage..ctor(Int32 db, CommandFlags flags, RedisCommand command, String script, RedisKey[] keys, RedisValue[] values) in //src/StackExchange.Redis/RedisDatabase.cs:line 4790
at StackExchange.Redis.RedisDatabase.ScriptEvaluateAsync(String script, RedisKey[] keys, RedisValue[] values, CommandFlags flags) in //src/StackExchange.Redis/RedisDatabase.cs:line 1547
at Microsoft.AspNetCore.OutputCaching.StackExchangeRedis.RedisOutputCacheStore.Microsoft.AspNetCore.OutputCaching.IOutputCacheBufferStore.SetAsync(String key, ReadOnlySequence1 value, ReadOnlyMemory1 tags, TimeSpan validFor, CancellationToken cancellationToken)
at Microsoft.AspNetCore.OutputCaching.OutputCacheEntryFormatter.StoreAsync(String key, OutputCacheEntry value, HashSet`1 tags, TimeSpan duration, IOutputCacheStore store, ILogger logger, CancellationToken cancellationToken)

.NET Version

8

Anything else?

No response

[abratv]

Just learned how to debug aspnetcore source code...

The issue caused by null tag (not the value of the cache itself)
I have more than one tags, one of it has null value

maybe context.Tags.Add(xxx); //if xxx is null, then throw over here already?

[abratv]

but having exception in policy is not nice
just log it with warn? reason is that cache tag may or may not available
the endpoint queries might be there or not there

[mgravell]

Propose there are 2 bugs here:

• the backend is the immediate bug; need to investigate
• IMO the middleware layer should mask such errors turning them into logged errors but making failed writes simply continue (logged) and failed reads (logged) manifest as misses