Unable to connect to the Redis server using Microsoft.AspNetCore.SignalR.StackExchangeRedis with .Net Aspire 13

Question

Unable to connect to the Redis server using Microsoft.AspNetCore.SignalR.StackExchangeRedis with .Net Aspire 13

Hoài Nam Nguyễn 81

I'm using .Net Aspire 13, .Net 10. I'm using the library package Include="Microsoft.AspNetCore.SignalR.StackExchangeRedis" Version="10.0.3". This is my AppHost:

var cache = builder.AddRedis("cache", 6379);

var presence = builder.AddProject<Projects.Chat_Presense>("chat-presense")    
    .WithReference(cache)
    .WaitFor(cache)
    .WithReference(keycloak)
    .WaitFor(keycloak)
    .WithEndpoint(port: 5001, targetPort: 6001, scheme: "http", name: "chat-presense", isExternal: true);

And in Projects.Chat_Presense, I configured Redis as follows:

builder.Services.AddSignalR().AddStackExchangeRedis("cache");

"ConnectionStrings": {
  "cache": "localhost:6379,password=FxxawDPpD1Tscj9pt2upxH,abortConnect=false"
}

but the error:

Microsoft.AspNetCore.SignalR.StackExchangeRedis.RedisHubLifetimeManager[14]

      Error connecting to Redis.

      StackExchange.Redis.RedisConnectionException: It was not possible to connect to the redis server(s). Error connecting right now. To allow this multiplexer to continue retrying until it's able to connect, use abortConnect=false in your connection string or AbortOnConnectFail=false; in your code.

         at StackExchange.Redis.ConnectionMultiplexer.ConnectImplAsync(ConfigurationOptions configuration, TextWriter writer, Nullable`1 serverType) in /_/src/StackExchange.Redis/ConnectionMultiplexer.cs:line 596

         at Microsoft.AspNetCore.SignalR.StackExchangeRedis.RedisOptions.ConnectAsync(TextWriter log)

         at Microsoft.AspNetCore.SignalR.StackExchangeRedis.RedisHubLifetimeManager`1.EnsureRedisServerConnection()

How do I fix this?

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Answer 1

Hi @Hoài Nam Nguyễn.

From what I've seen, you’re hitting these problems:

localhost is wrong in Aspire when your app runs in a container.

localhost:6379 from inside chat-presense points to the chat-presense container, not the Redis container. In Aspire, when you reference Redis with .WithReference(cache), Aspire injects the Redis connection info into the consuming project (including CACHE_HOST, CACHE_PORT, CACHE_URI, etc.). The Aspire Redis integration docs also explicitly show that WithReference(redis) “Provides ConnectionStrings__cache”. (aspire)

AddStackExchangeRedis("cache") does not mean “use the connection string named cache”.

That overload’s parameter is literally redisConnectionString: String — i.e., it expects the actual Redis connection string, not a key/name to look up in ConnectionStrings. (StackExchangeRedisDependencyInjectionExtensions.AddStackExchangeRedis Method)

This exact mismatch has been reported as a bug/pitfall with Aspire + SignalR backplane: config.GetConnectionString("redis-cache") has the right value at runtime, but passing the name into AddStackExchangeRedis("redis-cache") fails to connect. (Related issue)

To fix this, I'd suggest:

Read the connection string from configuration (which Aspire populates via WithReference(cache)) and pass the resolved value:


var redisCs = builder.Configuration.GetConnectionString("cache");

builder.Services

    .AddSignalR()

    .AddStackExchangeRedis(redisCs!, options =>

    {

        // optional: helpful if Redis may start slightly after the app

        options.Configuration.AbortOnConnectFail = false;

    });

And remove (or don’t use for container runs) the hardcoded localhost setting:


"ConnectionStrings": {

  "cache": "localhost:6379,..."

}

Let Aspire supply the correct Redis endpoint on the Aspire network via WithReference(cache) (ex: using the resource hostname like cache + port, not localhost). Disclaimer: Some links are non-Microsoft website. The pages appear to be providing accurate, safe information. Watch out for ads on the site that may advertise products frequently classifies as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the site before you decide to download and install it.

If you found my response helpful or informative, I would greatly appreciate it if you could follow this guidance or provide feedback. Thank you.

Answer 2

AddStackExchangeRedis expects either a full Redis connection string or a ConfigurationOptions object, not just the logical name of the connection string.

In the code, this line:

builder.Services.AddSignalR().AddStackExchangeRedis("cache");

passes the literal string "cache" to StackExchange.Redis, so it tries to connect to a server named cache on the default port, which fails.

Use the actual connection string instead, for example by reading it from configuration:

var redisConnectionString = builder.Configuration.GetConnectionString("cache");

builder.Services
    .AddSignalR()
    .AddStackExchangeRedis(redisConnectionString);

With the appsettings.json entry:

"ConnectionStrings": {
  "cache": "localhost:6379,password=FxxawDPpD1Tscj9pt2upxH,abortConnect=false"
}

Also ensure that the Redis server is actually running and reachable at localhost:6379 from the Chat_Presense project container/process. In containerized Aspire setups, localhost usually refers to the container itself, not the AppHost; use the service host name and port that Aspire assigns (for example, the resource name) in the connection string if needed.

References:

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Unable to connect to the Redis server using Microsoft.AspNetCore.SignalR.StackExchangeRedis with .Net Aspire 13

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