C#•4mo ago

Multi-Instance Application with SignalR and Redis as backplane

Hello :) I have an application that I want to have multi-instances of. The application communicates with the frontend via SignalR for various use-cases, but when I launch another instance of the application, the client often fails to connect to the SignalR Hub. This is how I set Redis as the backplane:

services.AddSignalR()
        .AddStackExchangeRedis(builder.Configuration.GetValue<string>("SignalR:RedisBackbone"),
                       options =>
                       {
                           options.Configuration.ChannelPrefix = redisChannel.Literal("Some:Prefix");
                       });

services.AddSignalR()
        .AddStackExchangeRedis(builder.Configuration.GetValue<string>("SignalR:RedisBackbone"),
                       options =>
                       {
                           options.Configuration.ChannelPrefix = redisChannel.Literal("Some:Prefix");
                       });

With a single instance it works perfectly fine, but when another instance is introduced, it fails to connect (not always, but quite often). This is the error I get on the client side:

Unable to connect to the server with any of the available transports. Error: WebSockets failed: Error: WebSocket failed to connect. The connection could not be found on the server, either the endpoint may not be a SignalR endpoint, the connection ID is not present on the server, or there is a proxy blocking WebSockets. If you have multiple servers check that sticky sessions are enabled. Error: ServerSentEvents failed: Error: EventSource failed to connect. The connection could not be found on the server, either the connection ID is not present on the server, or a proxy is refusing/buffering the connection. If you have multiple servers check that sticky sessions are enabled. Error: LongPolling failed: Error: No Connection with that ID: Status code '404'

Unable to connect to the server with any of the available transports. Error: WebSockets failed: Error: WebSocket failed to connect. The connection could not be found on the server, either the endpoint may not be a SignalR endpoint, the connection ID is not present on the server, or there is a proxy blocking WebSockets. If you have multiple servers check that sticky sessions are enabled. Error: ServerSentEvents failed: Error: EventSource failed to connect. The connection could not be found on the server, either the connection ID is not present on the server, or a proxy is refusing/buffering the connection. If you have multiple servers check that sticky sessions are enabled. Error: LongPolling failed: Error: No Connection with that ID: Status code '404'

I also tried using stateful-set for the deployment, but still no luck. Is there some specific configuration that needs to be set? NOTE: Redis is a single instance

1 Reply

Pan!cKk•4mo ago

UPDATE I believe the fix for this was configuring sticky-sessions on the ingress of the service in kubernetes, it seems to be working now

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Multi-Instance Application with SignalR and Redis as backplane