Executing Multi Slot commands through Envoy Proxy

[dceravigupta]

I have a cache which consists of multiple standalone Redis instances all behind an Envoy Proxy. As per the Envoy documentation, it is capable of fanning out a multi slot command like MGET to the right Redis instances based on its hash slot. It works as expected when I run such commands through redis-cli.

But in my .NET application, when I issue such command through StackExchange.Redis, it throws an exception saying Multi-key operations must involve a single slot; Wondering is there any way to execute such operations in my step?

StackExchange.Redis.RedisCommandException HResult=0x80131500 Message=Multi-key operations must involve a single slot; keys can use 'hash tags' to help this, i.e. '{/users/12345}/account' and '{/users/12345}/contacts' will always be in the same slot Source=StackExchange.Redis StackTrace: at StackExchange.Redis.ServerSelectionStrategy.Select(Message message, Boolean allowDisconnected) in /_/src/StackExchange.Redis/ServerSelectionStrategy.cs:line 148 at StackExchange.Redis.ConnectionMultiplexer.SelectServer(Message message) in /_/src/StackExchange.Redis/ConnectionMultiplexer.cs:line 1828 at StackExchange.Redis.ConnectionMultiplexer.PrepareToPushMessageToBridge[T](Message message, ResultProcessor1 processor, IResultBox1 resultBox, ServerEndPoint& server) in /_/src/StackExchange.Redis/ConnectionMultiplexer.cs:line 1843 at StackExchange.Redis.ConnectionMultiplexer.TryPushMessageToBridgeSync[T](Message message, ResultProcessor1 processor, IResultBox1 resultBox, ServerEndPoint& server) in /_/src/StackExchange.Redis/ConnectionMultiplexer.cs:line 1905 at StackExchange.Redis.ConnectionMultiplexer.ExecuteSyncImpl[T](Message message, ResultProcessor1 processor, ServerEndPoint server, T defaultValue) in /_/src/StackExchange.Redis/ConnectionMultiplexer.cs:line 1966
at StackExchange.Redis.RedisBase.ExecuteSync[T](Message message, ResultProcessor1 processor, ServerEndPoint server, T defaultValue) in /_/src/StackExchange.Redis/RedisBase.cs:line 62 at StackExchange.Redis.RedisDatabase.StringGet(RedisKey[] keys, CommandFlags flags) in /_/src/StackExchange.Redis/RedisDatabase.cs:line 3028 at Program.<Main>$(String[] args) in C:\Users\ravgup\source\repos\ConsoleApp14\ConsoleApp14\Program.cs:line 10

[mgravell]

Is there a documented list of which operations support this? We could simply let these through and let the server worry about it - it would be a simple case of changing the envoy handling here to simply do break; - I guess it depends on how universal this feature is. I'm guessing it doesn't apply to rpoplpush for example.

[dceravigupta]

@mgravell their documentation have not mentioned any such list. This is what their document mentioned on this topic.

https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/other_protocols/redis

Also, they don't support all the Redis commands at this moment and rpoplpush is one of them. They do have list of supported commands listed on the page above.

[mgravell]

Thoughts @NickCraver ? I'm thinking "disable the check" (i.e. just break; for envoy) - disagree at all?

[NickCraver]

+1 - this is only optimizing an error path to throw faster, if that's not 100% correct let's rip it out!

[mgravell]

PR: #2428

[dceravigupta]

Thanks @mgravell and @NickCraver!