ApsaraDB for Redis:How do I resolve the sudden increase in memory usage?

Problem description

An instance of Redis suddenly experiences a significant increase in memory usage, even reaching 100%.

Causes

The sudden increase in memory usage may be due to the following reasons:

• A large amount of new data is written in a short period of time.

• A large number of new connections are established in a short period of time.

• Burst access generates a large amount of traffic that exceeds the network bandwidth, resulting in a backlog in the input and output buffers.

• The client cannot keep up with the processing speed of Redis, resulting in a backlog in the output buffer.

Solutions

Identify the causes of the sudden increase in memory usage and use the suggested solutions to resolve the issue.

Check whether a large amount of new data is written

Troubleshooting method:

On the Performance Monitor page, check the inbound traffic and write queries per second (QPS) of the Redis instance. If the inbound traffic and write QPS follow the same trend as the memory usage, the sudden increase in memory usage is caused by a large amount of written data.

Solution:

1. Configure appropriate time-to-live (TTL) values for keys to automatically delete keys that are no longer needed, or manually delete unnecessary keys.

2. Upgrade the instance specifications by increasing the memory capacity to mitigate the sudden increase in memory usage. For more information, see Change the configurations of an instance.

3. If your instance is a standard instance and the memory usage remains high after you increase the memory capacity, you can upgrade the instance to a cluster instance. This way, you can distribute data across multiple data shards to reduce the memory pressure on individual data shards. For more information, see Change the configurations of an instance.

Check whether a large number of new connections are established

Troubleshooting method:

On the Performance Monitor page, view the number of connections to the Redis instance. If the number of connections suddenly increases and follows the same trend as the memory usage, the sudden increase in memory usage is caused by a large number of new connections.

Solution:

1. Check whether connection leaks exist.

2. Configure connection timeout periods to automatically close idle connections. For more information, see Specify a timeout period for client connections.

Check whether burst traffic causes backlog in the input and output buffers

Troubleshooting method:

1. Check whether the inbound and outbound traffic usage of the instance reaches 100%.

2. Run the MEMORY STATS command to check whether clients.normal occupies an excessive amount of memory.

   Note

   clients.normal reflects the total amount of memory that is used by the input and output buffers for all normal client connections.

Solution:

1. Check the cause of traffic burst.

2. Increase the network bandwidth of the instance. For more information, see Manually increase the bandwidth of an instance and Enable bandwidth auto scaling.

3. Upgrade the instance specifications to ensure optimal usage of the input and output buffers. For more information, see Change the configurations of an instance.

Check whether client-side performance issues cause backlog in the output buffer

Troubleshooting method:

In redis-cli, run the MEMORY DOCTOR command to view the value of big_client_buf. If big_client_buf is set to 1, at least one client has a large output buffer that consumes a significant amount of memory.

Solution:

Run the CLIENT LIST command to check which client has a large output buffer that consumes a significant amount of memory (omem). Check whether the client application has performance issues.