How to Solve It was not possible to connect to the redis server(s) Error in Azure

If you are using Azure to host your .NET Core applications that use Redis as a cache or a database, you may use the StackExchange.Redis library to communicate with the Redis server. However, you may encounter the following error message when you try to perform any operation with Redis:

It was not possible to connect to the redis server(s); to create a disconnected multiplexer, disable AbortOnConnectFail.

This error indicates that StackExchange.Redis cannot establish or maintain a connection to the Redis server, and it aborts the connection attempt. This can cause your application to fail or lose access to your Redis data.

In this post, we will show you how to troubleshoot and fix this error by checking and configuring your connection settings, updating your library version, or using other methods to connect to Redis.

How to check and configure your connection settings?

One of the possible causes of this error is that your connection settings are incorrect or insufficient. You need to provide a valid connection string or a ConfigurationOptions object to StackExchange.Redis when you create a ConnectionMultiplexer instance. The connection string or the ConfigurationOptions object should contain the following information:

The host name or IP address and port number of the Redis server. For example, localhost:6379 or 192.168.0.1:6379.
The password of the Redis server if it requires authentication. For example, password=123456.
The AbortOnConnectFail option that determines whether StackExchange.Redis should abort the connection attempt if it fails. The default value of this option is true, which means that StackExchange.Redis will not retry to connect if it encounters an error. However, this can cause problems if there is a temporary network issue or a high load on the server. Therefore, it is recommended to set this option to false, which means that StackExchange.Redis will retry to connect in the background until it succeeds. For example, abortConnect=false.

Here is an example of how to create a ConnectionMultiplexer instance with a connection string:

var connectionString = "localhost:6379,password=123456,abortConnect=false";
var connection = ConnectionMultiplexer.Connect(connectionString);

1 2	var connectionString = "localhost:6379,password=123456,abortConnect=false"; var connection = ConnectionMultiplexer.Connect(connectionString);

Here is an example of how to create a ConnectionMultiplexer instance with a ConfigurationOptions object:

var options = new ConfigurationOptions();
options.EndPoints.Add("localhost", 6379);
options.Password = "123456";
options.AbortOnConnectFail = false;
var connection = ConnectionMultiplexer.Connect(options);

var options = new ConfigurationOptions();

options.EndPoints.Add("localhost", 6379);

options.Password = "123456";

options.AbortOnConnectFail = false;

var connection = ConnectionMultiplexer.Connect(options);

You can also specify other options in your connection settings, such as ConnectTimeout, SyncTimeout, ConnectRetry, etc. You can find more details about these options here.

How to update your library version?

Another possible cause of this error is that you are using an outdated version of StackExchange.Redis that has some bugs or compatibility issues with your .NET Core version or your Redis server version. You should always use the latest stable version of StackExchange.Redis that supports your .NET Core version and your Redis server version.

You can update your StackExchange.Redis library by using NuGet Package Manager in Visual Studio or by using dotnet add package command in the command line. For example, to update StackExchange.Redis to version 2.2.88, you can run the following command:

dotnet add package StackExchange.Redis --version 2.2.88

1	dotnet add package StackExchange.Redis --version 2.2.88

You can find the latest version of StackExchange.Redis here.

How to use other methods to connect to Redis?

If you still cannot connect to Redis after checking and configuring your connection settings and updating your library version, you can try other methods to connect to Redis, such as:

Using telnet or ping commands to test the connectivity and latency between your application and your Redis server. For example, you can run the following commands in your terminal:

telnet localhost 6379
ping localhost

1 2	telnet localhost 6379 ping localhost

These commands will show you if you can reach the Redis server and how fast it responds.

Using redis-cli or other Redis clients to connect to Redis and perform some operations manually. For example, you can run the following commands in your terminal:

redis-cli -h localhost -p 6379 -a 123456
set foo bar
get foo

redis-cli -h localhost -p 6379 -a 123456

set foo bar

get foo

These commands will show you if you can authenticate and interact with Redis.

Using Azure Cache for Redis service instead of hosting your own Redis server. Azure Cache for Redis is a fully managed service that provides high-performance and scalable caching for your applications. You can use Azure Cache for Redis with StackExchange.Redis library by following these instructions.

Conclusion

The error It was not possible to connect to the redis server(s) occurs when StackExchange.Redis cannot establish or maintain a connection to the Redis server, and it aborts the connection attempt. This can cause your application to fail or lose access to your Redis data.

In this post, we showed you how to troubleshoot and fix this error by checking and configuring your connection settings, updating your library version, or using other methods to connect to Redis.

We hope this post has helped you understand and use StackExchange.Redis in Azure. If you have any questions or feedback, please leave a comment below.