Managed Redis fails with StackExchange.Redis.RedisConnectionException after a few days of usage and does not return to e healthy state

Question

Managed Redis fails with StackExchange.Redis.RedisConnectionException after a few days of usage and does not return to e healthy state

Sven Carstensen 0

We are using Azure Managed Redis, running in Balanced B0, size 0.5GB, location West Europe.

After a few days our Container Apps (.NET 9) cannot connect anymore and get the following two exceptions:

The message timed out in the backlog attempting to send because no connection became available (5000ms) - Last Connection Exception: UnableToConnect (0-sent) on XYZ.westeurope.redis.azure.net:10000/Interactive, Flushed/ReadAsync, last: ECHO, origin: ResetNonConnected, outstanding: 13, last-read: 5s ago, last-write: 4s ago, unanswered-write: 4s ago, keep-alive: 60s, state: ConnectedEstablishing, mgr: 10 of 10 available, last-heartbeat: never, global: 5s ago, v: 2.8.24.3255, command=HGET, timeout: 5000, inst: 0, qu: 2, qs: 0, aw: False, bw: CheckingForTimeout, rs: ReadAsync, ws: Idle, in: 0, last-in: 0, cur-in: 0, sync-ops: 0, async-ops: 9, serverEndpoint: XYZ.westeurope.redis.azure.net:10000, conn-sec: 22.99, aoc: 0, mc: 1/1/0, mgr: 10 of 10 available, clientName: abc (SE.Redis-v2.8.24.3255), IOCP: (Busy=0,Free=1000,Min=1,Max=1000), WORKER: (Busy=0,Free=32767,Min=1,Max=32767), POOL: (Threads=7,QueuedItems=0,CompletedItems=441,Timers=19), v: 2.8.24.3255

The message timed out in the backlog attempting to send because no connection became available (5000ms) - Last Connection Exception: It was not possible to connect to the redis server(s). There was an authentication failure; check that passwords (or client certificates) are configured correctly: (RedisServerException) Error: WRONGPASS invalid username-password pair ConnectTimeout, command=HMSET, timeout: 5000, inst: 0, qu: 1, qs: 0, aw: False, bw: CheckingForTimeout, rs: ReadAsync, ws: Idle, in: 0, last-in: 0, cur-in: 0, sync-ops: 9, async-ops: 568, serverEndpoint: XYZ.westeurope.redis.azure.net:10000, conn-sec: 16.79, aoc: 0, mc: 1/1/0, mgr: 10 of 10 available, clientName: ABC (SE.Redis-v2.8.24.3255), PerfCounterHelperkeyHashSlot: 10240, IOCP: (Busy=0,Free=1000,Min=1,Max=1000), WORKER: (Busy=77,Free=32690,Min=1,Max=32767), POOL: (Threads=106,QueuedItems=1,CompletedItems=2321851,Timers=27), v: 2.8.24.3255

We use a user managed identity to connect. That identity can connect to other services like Azure table. So, the identity is existing and valid.

The only way we could get Redis working again was by deleting and recreating the Redis resource.

Monitoring is not showing any problems: 2MB used. Server load 30 to 60% - which is interesting because our apps can't connect. Connected Clients and Total Operations show both 10 with Count aggregation.

Any idea what could cause this?

Mahesh Kurva 5,025 Reputation points Microsoft External Staff Moderator

2025-06-10T08:37:04.2633333+00:00
Hi Sven Carstensen,

Greetings!!

It looks like you're facing some connectivity issues with your Azure Managed Redis after a few days of usage. The exceptions indicate that your application is having trouble establishing connections and there could be various factors at play here.

Here's a breakdown of what you can do to troubleshoot and possibly resolve the issue:

Use Azure Redis SDK with Token Support

Consider using the Azure SDK for Redis or a wrapper that supports Azure AD token-based authentication with automatic refresh.

Manually Refresh Tokens

If you're sticking with StackExchange.Redis, you’ll need to:

Acquire a new token periodically (e.g., every 50 minutes).

Reconnect the Redis client with the new token.

Increase Connection Pool Size

Tune the ConnectionMultiplexer settings:

var options = ConfigurationOptions.Parse("your.redis.cache.windows.net:6380"); options.AbortOnConnectFail = false; options.ConnectRetry = 5; options.ConnectTimeout = 10000; options.SyncTimeout = 10000; options.DefaultDatabase = 0; options.ClientName = "YourApp"; options.KeepAlive = 180; options.Password = "your-access-key-or-token"; var redis = ConnectionMultiplexer.Connect(options);

Enable Redis logs and metrics in Azure Monitor to get deeper insights into connection issues.

The Balanced B0 tier is very limited (0.5 GB, low throughput). Consider upgrading to a higher tier if your workload is growing.

For more information, please refer the document:
https://learn.microsoft.com/en-us/azure/redis/troubleshoot-connectivity

https://learn.microsoft.com/en-us/azure/redis/troubleshoot-connectivity

I hope this information helps. Please do let us know if you have any further queries.
Sven Carstensen 0 Reputation points

2025-06-10T08:50:54.0966667+00:00

We are using the HybridCache class which we add with dependency injection like so:

services.AddStackExchangeRedisCache(...);

services.AddHybridCache(...);

Where should we add code to manually refresh tokens and/or tune the ConnectionMultiplexer?
Sven Carstensen 0 Reputation points

2025-06-10T08:53:06.5566667+00:00

As a side note: restarting the container apps does not help - I would expect that restarting the container apps would fetch new tokens?
Mahesh Kurva 5,025 Reputation points Microsoft External Staff Moderator

2025-06-10T09:23:47.3066667+00:00
Hi Sven Carstensen,

Thanks for getting back to me.

restarting the container apps does not help

You're right to expect that restarting the container should fetch a new token. However, if the token is cached or the Redis client is not reinitialized properly with the new token, the issue can persist. Also, if the HybridCache or RedisCache is initialized early in the app lifecycle and holds onto a stale token, the restart won’t help unless the token acquisition logic is refreshed too.

Customizing Redis Connection with Token Refresh:

To manually refresh tokens and configure the ConnectionMultiplexer, you’ll need to bypass AddStackExchangeRedisCache and instead register a custom implementation. Here's a high-level approach:

Manually acquire a token using AzureServiceTokenProvider or DefaultAzureCredential.

Create a ConnectionMultiplexer using the token.

Register it as a singleton in the DI container.

Use it in a custom IDistributedCache implementation or inject it into your HybridCache.

Try this :

public static async Task CreateRedisConnectionAsync() { var credential = new DefaultAzureCredential(); var tokenRequestContext = new TokenRequestContext(new[] { "https://*.cacheinfra.windows.net:10225/appid/.default" }); var token = await credential.GetTokenAsync(tokenRequestContext); var options = new ConfigurationOptions { EndPoints = { "your-redis-name.redis.cache.windows.net:6380" }, Ssl = true, AbortOnConnectFail = false, Password = token.Token }; return await ConnectionMultiplexer.ConnectAsync(options); }

Then in Startup.cs or Program.cs:

builder.Services.AddSingleton(async provider => { var multiplexer = await CreateRedisConnectionAsync(); return multiplexer; });

I hope this information helps. Please do let us know if you have any further queries.
Sven Carstensen 0 Reputation points

2025-06-10T10:30:04.3766667+00:00

Thank you for the starter. I got that working with our user managed identity like so:

var credential = new DefaultAzureCredential(new DefaultAzureCredentialOptions { ManagedIdentityClientId = "our-user-managed-identity-id"} );

But isn't that only creating the token during startup and does not refresh it later?

How would I refresh that token?
Mahesh Kurva 5,025 Reputation points Microsoft External Staff Moderator

2025-06-10T11:23:09.4966667+00:00
Hi Sven Carstensen,

Yes, you're absolutely right.

var credential = new DefaultAzureCredential(new DefaultAzureCredentialOptions { ManagedIdentityClientId = "our-user-managed-identity-id"} );

only fetches the token once when you call GetTokenAsync(). It does not automatically refresh the token later unless you implement that logic yourself.

How would I refresh that token?

To handle token refresh properly, you need to:

Cache the token and track its expiration.

Refresh it proactively before it expires (e.g., 5 minutes before).

Recreate the Redis connection with the new token.

I hope this information helps. Please do let us know if you have any further queries.
Sven Carstensen 0 Reputation points

2025-06-10T11:38:50.87+00:00

Aren't the services I added fixed after I called Build() on the app builder?

How would I bring the recreated Redis connection into usage with dependency injection?
Sven Carstensen 0 Reputation points

2025-06-10T15:23:43.35+00:00
I tried to use the custom ConnectionMultiplexer created in CreateRedisConnectionAsync as an option to AddStackExchangeRedisCache by setting ConnectionMultiplexerFactory. But that gives authentication errors.

Returning to the old code ConfigureForAzureWithUserAssignedManagedIdentityAsync still produced the Auth failures.

I am at a loss why the Redis Cache is not allowing our user managed identity to connect.

New code snippet:

var configurationOptions = ConfigurationOptions.Parse(cacheOptions.DistributedCacheEndpoint!); services.AddStackExchangeRedisCache(options => { options.InstanceName = cacheOptions.InstanceName; options.ConfigurationOptions = configurationOptions; options.ConnectionMultiplexerFactory = async () => { var connectionMultiplexer = await CreateRedisConnectionAsync(cacheOptions); return connectionMultiplexer; }; });

I tried your proposed scope "https://*.cacheinfra.windows.net:10225/appid/.default" as well as "https://redis.azure.com/.default". Both returned a token, but both would lead to Auth failures on Redis

Old code is adding the MSI ID like so and does not use CreateRedisConnectionAsync:

var configurationOptions = ConfigurationOptions.Parse(cacheOptions.DistributedCacheEndpoint!);

configurationOptions.ConfigureForAzureWithUserAssignedManagedIdentityAsync(cacheOptions.UserManagedIdentityClientId!.Value.ToString());

Auth error looks like so:

AuthenticationFailure on xyz.westeurope.redis.azure.net:10000/Interactive, Flushed/ComputeResult, last: ECHO, origin: SetResult, outstanding: 0, last-read: 0s ago, last-write: 0s ago, keep-alive: 60s, state: ConnectedEstablishing, mgr: 10 of 10 available, last-heartbeat: never, global: 0s ago, v: 2.8.24.3255 Error: NOAUTH Authentication required Verify if the Redis password provided is correct. Attempted command: ECHO

Is it really a token problem or is Redis in a corrupt state?
Sven Carstensen 0 Reputation points

2025-06-10T19:32:46.52+00:00
After redeploying the Managed Redis resource our old code which uses

configurationOptions.ConfigureForAzureWithUserAssignedManagedIdentityAsync(cacheOptions.UserManagedIdentityClientId!.Value.ToString()); services.AddStackExchangeRedisCache(options => { options.InstanceName = cacheOptions.InstanceName; options.ConfigurationOptions = configurationOptions; });

The connection is working again.

Switching to CreateRedisConnectionAsync which creates a token on its own, I get authentication errors. The tokens look ok: I find our tenant id, the client ID of the user managed identity and the audience "https://redis.azure.com" in that token.

options.ConnectionMultiplexerFactory = async () => { var connectionMultiplexer = await CreateRedisConnectionAsync(cacheOptions); return connectionMultiplexer; };

Is there any documentation how to create a working token for Managed Redis with a user managed identity?
Sven Carstensen 0 Reputation points

2025-06-10T20:49:02.26+00:00
Some more digging: if I pass the token as password I need to set the User name to the ID of the managed identity - "1234-5678" in the following example.

public static async Task CreateRedisConnectionAsync() { var credential = new DefaultAzureCredential(new DefaultAzureCredentialOptions { ManagedIdentityClientId = "1234-5678"); var tokenRequestContext = new TokenRequestContext(new[] { "https://redis.azure.com/.default" }); var token = await credential.GetTokenAsync(tokenRequestContext); var options = new ConfigurationOptions { EndPoints = { "your-redis-name.redis.azure..net:somePort" }, Ssl = true, AbortOnConnectFail = false, User = "1234-5678" Password = token.Token }; return await ConnectionMultiplexer.ConnectAsync(options); }

Now I can connect to Redis.

Question remains, how to refresh the token after I called ConnectionMultiplexer.ConnextAsync and added that to the service collection.

And for our previous code, where we used this nuget, the documentation states that the refresh takes place: 'configures a StackExchange.Redis connection to use the token for authentication. It also maintains the token, proactively refreshing it and re-authenticating the connection to maintain uninterrupted communication with the cache over multiple days'.

Not sure why they say "over multiple days" and not "forever".
Mahesh Kurva 5,025 Reputation points Microsoft External Staff Moderator

2025-06-11T12:37:33.0533333+00:00

Hi Sven Carstensen,

Could you please share the details requested in the private message?
Mahesh Kurva 5,025 Reputation points Microsoft External Staff Moderator

2025-06-11T17:06:52.5566667+00:00
Hi Sven Carstensen,

Typically, we see TimeOutException errors being raised by StackExchange Redis due to client-side threading or performance issues. I notice the following output from the exception:

(RedisServerException) Error: WRONGPASS invalid username-password pair ConnectTimeout, command=HMSET, timeout: 5000, inst: 0, qu: 1, qs: 0, aw: False, bw: CheckingForTimeout, rs: ReadAsync, ws: Idle, in: 0, last-in: 0, cur-in: 0, sync-ops: 9, async-ops: 568, serverEndpoint: XYZ.westeurope.redis.azure.net:10000, conn-sec: 16.79, aoc: 0, mc: 1/1/0, mgr: 10 of 10 available, clientName: ABC (SE.Redis-v2.8.24.3255), PerfCounterHelperkeyHashSlot: 10240, IOCP: (Busy=0,Free=1000,Min=1,Max=1000), WORKER: (Busy=77,Free=32690,Min=1,Max=32767), POOL: (Threads=106,QueuedItems=1,CompletedItems=2321851,Timers=27), v: 2.8.24.3255

You can see .NET threadpool worker thread busy count is currently 77 while the minimum thread count is 1.

Anytime busy counter for IOCP or worker threads is > the Min count the .NET thread pool will throttle the creation of new threads. This can lead to Redis timeouts.

You can find details here:

https://azure.microsoft.com/en-us/documentation/articles/cache-faq/#important-details-about-threadpool-growth https://gist.github.com/JonCole/db0e90bedeb3fc4823c2#burst-of-traffic

Cache management FAQs - Azure Cache for Redis | Microsoft Learn

Another thing that leads to the timeouts are client-side performance issues particular high CPU and/or memory usage of the Redis client application. You can find details about the other client-side issues that can cause Redis client timeouts here: https://gist.github.com/JonCole/db0e90bedeb3fc4823c2

I have the following recommendations:

Please following the recommendation from this link to raise the minimum thread count. You can do this in your code. For Worker Roles you can do this at the beginning of your role's Run method, or for Web Roles or Web Apps you can do this as the first line of code in your global.asax.cs Application_Start(). Here is the line of code to add:
System.Threading.ThreadPool.SetMinThreads(200, 200);
NOTE: When configuring this in code this is not a per-core setting, the value you specify in code will be the value used for the Min counts. The Min value you set will depend on the load you expect on the application. 200 is a good starting value, but if your busy count exceeds 200 then you may need to raise it higher.

When you raise the Min thread counts this will allow more requests to run simultaneously because you remove the throttling so this will put additional resource usage on your client instances. You need to monitor this web application and VM hosting the web application for memory usage and CPU utilization. If you see these spike during the time you are receiving the Redis timeout errors then I recommend fixing the issue causing high memory and/or CPU utilization. This might include scaling out to more instances or scaling up to a larger VM size. Please see https://gist.github.com/I90Runner/911cd00ceeeeb473074c4e320e9fa287 .

I hope this information helps. Please do let us know if you have any further queries.
Sven Carstensen 0 Reputation points

2025-06-12T07:00:51.7666667+00:00

I switched back to ConfigureForAzureWithUserAssignedManagedIdentityAsync and redeployed our containers. Now we typically have to wait a few days until the connection problems to Redis start.

Are you sure that our issue is a client side one? Should not restarting the containers fix that problem, if its client based? We cannot fix that error with client restarts, only deleting and recreating the Redis instance helped up.

When the error reoccurs I will add the call to SetMinThreads.

1 answer

Your answer

Mahesh Kurva 5,025 Reputation points Microsoft External Staff Moderator

2025-06-10T08:37:04.2633333+00:00

Hi Sven Carstensen,

Greetings!!

It looks like you're facing some connectivity issues with your Azure Managed Redis after a few days of usage. The exceptions indicate that your application is having trouble establishing connections and there could be various factors at play here.

Here's a breakdown of what you can do to troubleshoot and possibly resolve the issue:

Use Azure Redis SDK with Token Support

Consider using the Azure SDK for Redis or a wrapper that supports Azure AD token-based authentication with automatic refresh.

Manually Refresh Tokens

If you're sticking with StackExchange.Redis, you’ll need to:

Acquire a new token periodically (e.g., every 50 minutes).

Reconnect the Redis client with the new token.

Increase Connection Pool Size

Tune the ConnectionMultiplexer settings:

var options = ConfigurationOptions.Parse("your.redis.cache.windows.net:6380"); options.AbortOnConnectFail = false; options.ConnectRetry = 5; options.ConnectTimeout = 10000; options.SyncTimeout = 10000; options.DefaultDatabase = 0; options.ClientName = "YourApp"; options.KeepAlive = 180; options.Password = "your-access-key-or-token"; var redis = ConnectionMultiplexer.Connect(options);

Enable Redis logs and metrics in Azure Monitor to get deeper insights into connection issues.

The Balanced B0 tier is very limited (0.5 GB, low throughput). Consider upgrading to a higher tier if your workload is growing.

For more information, please refer the document:
https://learn.microsoft.com/en-us/azure/redis/troubleshoot-connectivity

https://learn.microsoft.com/en-us/azure/redis/troubleshoot-connectivity

I hope this information helps. Please do let us know if you have any further queries.
Sven Carstensen 0 Reputation points

2025-06-10T08:50:54.0966667+00:00

We are using the HybridCache class which we add with dependency injection like so:

services.AddStackExchangeRedisCache(...);

services.AddHybridCache(...);

Where should we add code to manually refresh tokens and/or tune the ConnectionMultiplexer?
Sven Carstensen 0 Reputation points

2025-06-10T08:53:06.5566667+00:00

As a side note: restarting the container apps does not help - I would expect that restarting the container apps would fetch new tokens?
Mahesh Kurva 5,025 Reputation points Microsoft External Staff Moderator

2025-06-10T09:23:47.3066667+00:00

Hi Sven Carstensen,

Thanks for getting back to me.

restarting the container apps does not help

You're right to expect that restarting the container should fetch a new token. However, if the token is cached or the Redis client is not reinitialized properly with the new token, the issue can persist. Also, if the HybridCache or RedisCache is initialized early in the app lifecycle and holds onto a stale token, the restart won’t help unless the token acquisition logic is refreshed too.

Customizing Redis Connection with Token Refresh:

To manually refresh tokens and configure the ConnectionMultiplexer, you’ll need to bypass AddStackExchangeRedisCache and instead register a custom implementation. Here's a high-level approach:

Manually acquire a token using AzureServiceTokenProvider or DefaultAzureCredential.

Create a ConnectionMultiplexer using the token.

Register it as a singleton in the DI container.

Use it in a custom IDistributedCache implementation or inject it into your HybridCache.

Try this :

public static async Task CreateRedisConnectionAsync() { var credential = new DefaultAzureCredential(); var tokenRequestContext = new TokenRequestContext(new[] { "https://*.cacheinfra.windows.net:10225/appid/.default" }); var token = await credential.GetTokenAsync(tokenRequestContext); var options = new ConfigurationOptions { EndPoints = { "your-redis-name.redis.cache.windows.net:6380" }, Ssl = true, AbortOnConnectFail = false, Password = token.Token }; return await ConnectionMultiplexer.ConnectAsync(options); }

Then in Startup.cs or Program.cs:

builder.Services.AddSingleton(async provider => { var multiplexer = await CreateRedisConnectionAsync(); return multiplexer; });

I hope this information helps. Please do let us know if you have any further queries.
Sven Carstensen 0 Reputation points

2025-06-10T10:30:04.3766667+00:00

Thank you for the starter. I got that working with our user managed identity like so:

var credential = new DefaultAzureCredential(new DefaultAzureCredentialOptions { ManagedIdentityClientId = "our-user-managed-identity-id"} );

But isn't that only creating the token during startup and does not refresh it later?

How would I refresh that token?
Mahesh Kurva 5,025 Reputation points Microsoft External Staff Moderator

2025-06-10T11:23:09.4966667+00:00

Hi Sven Carstensen,

Yes, you're absolutely right.

var credential = new DefaultAzureCredential(new DefaultAzureCredentialOptions { ManagedIdentityClientId = "our-user-managed-identity-id"} );

only fetches the token once when you call GetTokenAsync(). It does not automatically refresh the token later unless you implement that logic yourself.

How would I refresh that token?

To handle token refresh properly, you need to:

Cache the token and track its expiration.

Refresh it proactively before it expires (e.g., 5 minutes before).

Recreate the Redis connection with the new token.

I hope this information helps. Please do let us know if you have any further queries.
Sven Carstensen 0 Reputation points

2025-06-10T11:38:50.87+00:00

Aren't the services I added fixed after I called Build() on the app builder?

How would I bring the recreated Redis connection into usage with dependency injection?
Sven Carstensen 0 Reputation points

2025-06-10T15:23:43.35+00:00

I tried to use the custom ConnectionMultiplexer created in CreateRedisConnectionAsync as an option to AddStackExchangeRedisCache by setting ConnectionMultiplexerFactory. But that gives authentication errors.

Returning to the old code ConfigureForAzureWithUserAssignedManagedIdentityAsync still produced the Auth failures.

I am at a loss why the Redis Cache is not allowing our user managed identity to connect.

New code snippet:

var configurationOptions = ConfigurationOptions.Parse(cacheOptions.DistributedCacheEndpoint!); services.AddStackExchangeRedisCache(options => { options.InstanceName = cacheOptions.InstanceName; options.ConfigurationOptions = configurationOptions; options.ConnectionMultiplexerFactory = async () => { var connectionMultiplexer = await CreateRedisConnectionAsync(cacheOptions); return connectionMultiplexer; }; });

I tried your proposed scope "https://*.cacheinfra.windows.net:10225/appid/.default" as well as "https://redis.azure.com/.default". Both returned a token, but both would lead to Auth failures on Redis

Old code is adding the MSI ID like so and does not use CreateRedisConnectionAsync:

var configurationOptions = ConfigurationOptions.Parse(cacheOptions.DistributedCacheEndpoint!);

configurationOptions.ConfigureForAzureWithUserAssignedManagedIdentityAsync(cacheOptions.UserManagedIdentityClientId!.Value.ToString());

Auth error looks like so:

AuthenticationFailure on xyz.westeurope.redis.azure.net:10000/Interactive, Flushed/ComputeResult, last: ECHO, origin: SetResult, outstanding: 0, last-read: 0s ago, last-write: 0s ago, keep-alive: 60s, state: ConnectedEstablishing, mgr: 10 of 10 available, last-heartbeat: never, global: 0s ago, v: 2.8.24.3255 Error: NOAUTH Authentication required Verify if the Redis password provided is correct. Attempted command: ECHO

Is it really a token problem or is Redis in a corrupt state?
Sven Carstensen 0 Reputation points

2025-06-10T19:32:46.52+00:00

After redeploying the Managed Redis resource our old code which uses

configurationOptions.ConfigureForAzureWithUserAssignedManagedIdentityAsync(cacheOptions.UserManagedIdentityClientId!.Value.ToString()); services.AddStackExchangeRedisCache(options => { options.InstanceName = cacheOptions.InstanceName; options.ConfigurationOptions = configurationOptions; });

The connection is working again.

Switching to CreateRedisConnectionAsync which creates a token on its own, I get authentication errors. The tokens look ok: I find our tenant id, the client ID of the user managed identity and the audience "https://redis.azure.com" in that token.

options.ConnectionMultiplexerFactory = async () => { var connectionMultiplexer = await CreateRedisConnectionAsync(cacheOptions); return connectionMultiplexer; };

Is there any documentation how to create a working token for Managed Redis with a user managed identity?
Sven Carstensen 0 Reputation points

2025-06-10T20:49:02.26+00:00

Some more digging: if I pass the token as password I need to set the User name to the ID of the managed identity - "1234-5678" in the following example.

public static async Task CreateRedisConnectionAsync() { var credential = new DefaultAzureCredential(new DefaultAzureCredentialOptions { ManagedIdentityClientId = "1234-5678"); var tokenRequestContext = new TokenRequestContext(new[] { "https://redis.azure.com/.default" }); var token = await credential.GetTokenAsync(tokenRequestContext); var options = new ConfigurationOptions { EndPoints = { "your-redis-name.redis.azure..net:somePort" }, Ssl = true, AbortOnConnectFail = false, User = "1234-5678" Password = token.Token }; return await ConnectionMultiplexer.ConnectAsync(options); }

Now I can connect to Redis.

Question remains, how to refresh the token after I called ConnectionMultiplexer.ConnextAsync and added that to the service collection.

And for our previous code, where we used this nuget, the documentation states that the refresh takes place: 'configures a StackExchange.Redis connection to use the token for authentication. It also maintains the token, proactively refreshing it and re-authenticating the connection to maintain uninterrupted communication with the cache over multiple days'.

Not sure why they say "over multiple days" and not "forever".
Mahesh Kurva 5,025 Reputation points Microsoft External Staff Moderator

2025-06-11T12:37:33.0533333+00:00

Hi Sven Carstensen,

Could you please share the details requested in the private message?
Sven Carstensen 0 Reputation points

2025-06-12T07:00:51.7666667+00:00

I switched back to ConfigureForAzureWithUserAssignedManagedIdentityAsync and redeployed our containers. Now we typically have to wait a few days until the connection problems to Redis start.

Are you sure that our issue is a client side one? Should not restarting the containers fix that problem, if its client based? We cannot fix that error with client restarts, only deleting and recreating the Redis instance helped up.

When the error reoccurs I will add the call to SetMinThreads.

Answer 1

PratikLad 1,825 Microsoft External Staff Moderator

Hi Sven Carstensen,

You can refer to the official Document on Cache management FAQs - Azure Cache for Redis | Microsoft Learn for detailed information.

The timeout exception and the following connection error from StackExchange.Redis indicate potential client-side performance bottlenecks, particularly related to .NET ThreadPool usage:


RedisServerException) Error: WRONGPASS invalid username-password pair ConnectTimeout, command=HMSET, timeout: 5000, inst: 0, qu: 1, qs: 0, aw: False, bw: CheckingForTimeout, rs: ReadAsync, ws: Idle, in: 0, last-in: 0, cur-in: 0, sync-ops: 9, async-ops: 568, serverEndpoint: XYZ.westeurope.redis.azure.net:10000, conn-sec: 16.79, aoc: 0, mc: 1/1/0, mgr: 10 of 10 available, clientName: ABC (SE.Redis-v2.8.24.3255), PerfCounterHelperkeyHashSlot: 10240, IOCP: (Busy=0,Free=1000,Min=1,Max=1000), WORKER: (**Busy=77**,Free=32690,Min=1,Max=32767), POOL: (Threads=106,QueuedItems=1,CompletedItems=2321851,Timers=27), v: 2.8.24.3255

This log shows that 77 worker threads were busy at the time of the failure, while the ThreadPool’s minimum thread count was just 1.

When the number of busy threads exceeds the minimum, the .NET ThreadPool throttles thread creation, which can delay Redis operations and lead to TimeoutException errors. You can read more about this behavior in:

Increase the minimum thread count early in your app's lifecycle. Add this line of code as early as possible (e.g., in Program.cs, Application_Start(), or the main method):


System.Threading.ThreadPool.SetMinThreads(200, 200);

This is not per-core: the values apply globally.
Start with 200 and monitor; if the busy thread count still exceeds that, increase accordingly.

Monitor CPU and memory usage of the container or VM. If your Redis client is under heavy CPU/memory load, this can exacerbate timeouts.

Scale your application appropriately:

If utilization remains high, consider scaling out (more instances) or scaling up (larger size).
Refer to this guide on scaling and resource impact: Redis timeouts and client-side pressure

While these client-side performance improvements are crucial, please note that the "WRONGPASS" error also indicates a possible authentication issue (e.g., with Managed Identity or token expiration). If you're using Azure Managed Identity, ensure token handling and Redis connection setup are configured correctly.

PratikLad 1,825 Reputation points Microsoft External Staff Moderator

2025-06-20T13:39:52.0966667+00:00

We have sent you an email requesting the server details and kindly ask you to respond with the requested information. Please note that we have recorded your email address and will now remove it from the Q&A forum for privacy reasons.
PratikLad 1,825 Reputation points Microsoft External Staff Moderator

2025-06-23T07:53:17.07+00:00

We have sent you an email requesting the server details and kindly ask you to respond with the requested information. Please note that we have recorded your email address and will now remove it from the Q&A forum for privacy reasons.
Sven Carstensen 0 Reputation points

2025-06-23T08:46:03.13+00:00

Hi PratikLad, I checked my emails and did not find an email asking about server details. Can you please resend or PM me?
Sven Carstensen 0 Reputation points

2025-06-23T08:50:09.2233333+00:00

Currently the Redis instance doesn't let us connect again:

The message timed out in the backlog attempting to send because no connection became available (5000ms) - Last Connection Exception: It was not possible to connect to the redis server(s). ConnectTimeout, command=HGET, timeout: 5000, inst: 0, qu: 0, qs: 0, aw: False, bw: CheckingForTimeout, rs: ReadAsync, ws: Idle, in: 0, last-in: 0, cur-in: 0, sync-ops: 8, async-ops: 62397, serverEndpoint: 50.85.28.135:8500, conn-sec: 39.99, aoc: 0, mc: 1/1/0, mgr: 10 of 10 available, clientName: XYZ (SE.Redis-v2.8.24.3255), PerfCounterHelperkeyHashSlot: 13306, IOCP: (Busy=0,Free=1000,Min=1,Max=1000), WORKER: (Busy=0,Free=32767,Min=1,Max=32767), POOL: (Threads=2,QueuedItems=0,CompletedItems=726413,Timers=8), v: 2.8.24.3255

We redeployed our container apps to set min thread pool size to 200 which does not help.

The message timed out in the backlog attempting to send because no connection became available (5000ms) - Last Connection Exception: UnableToConnect (0-sent) on XYZ.redis.azure.net:10000/Interactive, Flushed/ReadAsync, last: ECHO, origin: ResetNonConnected, outstanding: 13, last-read: 5s ago, last-write: 4s ago, unanswered-write: 4s ago, keep-alive: 60s, state: ConnectedEstablishing, mgr: 10 of 10 available, last-heartbeat: never, global: 5s ago, v: 2.8.24.3255, command=HMSET, timeout: 5000, inst: 0, qu: 1, qs: 0, aw: False, bw: CheckingForTimeout, rs: ReadAsync, ws: Idle, in: 0, last-in: 0, cur-in: 0, sync-ops: 0, async-ops: 11, serverEndpoint: XYZ.redis.azure.net:10000, conn-sec: 28.99, aoc: 0, mc: 1/1/0, mgr: 10 of 10 available, clientName: ABC (SE.Redis-v2.8.24.3255), IOCP: (Busy=0,Free=1000,Min=200,Max=1000), WORKER: (Busy=4,Free=32763,Min=200,Max=32767), POOL: (Threads=11,QueuedItems=1,CompletedItems=7148,Timers=25), v: 2.8.24.3255
Oury Ba-MSFT 20,911 Reputation points Microsoft Employee Moderator

2025-06-26T19:09:35.4233333+00:00

Sven Carstensen Thank you for reaching out.

Are you using Microsoft.Azure.StackExchangeRedis v3.2.1?
Sven Carstensen 0 Reputation points

2025-06-27T06:34:52.02+00:00

Yes, 3.2.1

Microsoft.Azure.StackExchangeRedis Version="3.2.1"

Microsoft.Extensions.Caching.Hybrid Version="9.5.0"

Microsoft.Extensions.Caching.StackExchangeRedis Version="9.0.5"

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Managed Redis fails with StackExchange.Redis.RedisConnectionException after a few days of usage and does not return to e healthy state

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