Configuring Redis

Using an alternate local Redis instance

Omnibus GitLab includes Redis by default. To direct the GitLab application to your own locally running Redis instance:

  1. Edit /etc/gitlab/gitlab.rb: 

    # Disable the bundled Redis
redis['enable'] = false

# Redis via TCP
gitlab_rails['redis_host'] = '127.0.0.1'
gitlab_rails['redis_port'] = 6379

# OR Redis via Unix domain sockets
gitlab_rails['redis_socket'] = '/tmp/redis.sock' # defaults to /var/opt/gitlab/redis/redis.socket

# Password to Authenticate to alternate local Redis if required
gitlab_rails['redis_password'] = '<redis_password>'

  2. Reconfigure GitLab for the changes to take effect: 

    sudo gitlab-ctl reconfigure

Making the bundled Redis reachable via TCP

Use the following settings if you want to make the Redis instance managed by Omnibus GitLab reachable via TCP:

  1. Edit /etc/gitlab/gitlab.rb: 

    redis['port'] = 6379
redis['bind'] = '127.0.0.1'

  2. Save the file and reconfigure GitLab for the changes to take effect: 

    sudo gitlab-ctl reconfigure

Setting up a Redis-only server using Omnibus GitLab

If you’d like to set up Redis in a separate server than the GitLab application, you can use the bundled Redis in Omnibus GitLab.

Running with multiple Redis instances

See https://docs.gitlab.com/ee/administration/redis/replication_and_failover.html#running-multiple-redis-clusters.

Redis Sentinel

See https://docs.gitlab.com/ee/administration/redis/replication_and_failover.html.

Using Redis in a failover setup

See https://docs.gitlab.com/ee/administration/redis/replication_and_failover.html.

Using Google Cloud Memorystore

Google Cloud Memorystore does not support the Redis CLIENT command. By default Sidekiq will attempt to set the CLIENT for debugging purposes. This can be disabled via this configuration setting: 

gitlab_rails['redis_enable_client'] = false

Increasing the number of Redis connections beyond the default

By default Redis will only accept 10,000 client connections. If you need more that 10,000 connections set the maxclients attribute to suit your needs. Be advised that adjusting the maxclients attribute means that you will also need to take into account your systems settings for fs.file-max (for example sysctl -w fs.file-max=20000) 

redis['maxclients'] = 20000

Tuning the TCP stack for Redis

The following settings are to enable a more performant Redis server instance. tcp_timeout is a value set in seconds that the Redis server waits before terminating an idle TCP connection. The tcp_keepalive is a tunable setting in seconds to TCP ACKs to clients in absence of communication. 

redis['tcp_timeout'] = "60"
redis['tcp_keepalive'] = "300"

Setting the Redis Cache instance as an LRU

Using multiple Redis instances allows you to configure Redis as a Least Recently Used cache. Note you should only do this for the Redis cache instance; the Redis queues and shared state instances should never be configured as an LRU, since they contain data (e.g. Sidekiq jobs) that is expected to be persistent.

To cap memory usage at 32GB, you can use: 

redis['maxmemory'] = "32gb"
redis['maxmemory_policy'] = "allkeys-lru"
redis['maxmemory_samples'] = 5

Using Secure Sockets Layer (SSL)

Redis 5.x does NOT support SSL out of the box. However, you can encrypt a Redis connection using stunnel. AWS ElasticCache also supports Redis over SSL.

Support for SSL has the following limitations:

  • Omnibus GitLab doesn’t include stunnel or other tools to provide encryption for the Redis server. However, GitLab does provide client support by using the rediss:// (as opposed to redis://) URL scheme.
  • Omnibus GitLab bundles Redis Sentinel 5.0.x which does NOT support SSL. If you use Redis Sentinel, do not activate client support for SSL. Redis 6 supports SSL, and you can configure it to work with GitLab only as an external service.

To activate GitLab client support for SSL:

  1. Add the following line to /etc/gitlab/gitlab.rb: 

    gitlab_rails['redis_ssl'] = true

  2. Reconfigure GitLab for the changes to take effect: 

    sudo gitlab-ctl reconfigure

SSL certificates

If you’re using custom SSL certificates for Redis, be sure to add them to the trusted certificates.

Renamed commands

By default, the KEYS command is disabled as a security measure.

If you’d like to obfuscate or disable this command, or other commands, edit the redis['rename_commands'] setting in /etc/gitlab/gitlab.rb to look like: 

redis['rename_commands'] = {
  'KEYS': '',
  'OTHER_COMMAND': 'VALUE'
}
  • OTHER_COMMAND is the command you want to modify
  • VALUE should be one of:
    1. A new command name.
    2. '', which completely disables the command.

To disable this functionality:

  1. Set redis['rename_commands'] = {} in your /etc/gitlab/gitlab.rb file
  2. Run sudo gitlab-ctl reconfigure

Lazy freeing

Redis 4 introduced lazy freeing. This can improve performance when freeing large values.

This setting defaults to false. To enable it, you can use: 

redis['lazyfree_lazy_eviction'] = true
redis['lazyfree_lazy_expire'] = true
redis['lazyfree_lazy_server_del'] = true
redis['replica_lazy_flush'] = true

Threaded I/O

Redis 6 introduced threaded I/O. This allow writes to scale across multiple cores.

This setting is disabled by default. To enable it, you can use: 

redis['io_threads'] = 4
redis['io_threads_do_reads'] = true

Troubleshooting

x509: certificate signed by unknown authority

This error message suggests that the SSL certificates have not been properly added to the list of trusted certificates for the server. To check whether this is an issue:

  1. Check Workhorse logs in /var/log/gitlab/gitlab-workhorse/current.

  2. If you see messages that look like: 

    2018-11-14_05:52:16.71123 time="2018-11-14T05:52:16Z" level=info msg="redis: dialing" address="redis-server:6379" scheme=rediss
2018-11-14_05:52:16.74397 time="2018-11-14T05:52:16Z" level=error msg="unknown error" error="keywatcher: x509: certificate signed by unknown authority"

    The first line should show rediss as the scheme with the address of the Redis server. The second line indicates the certificate is not properly trusted on this server. See the previous section.

  3. Verify that the SSL certificate is working via these troubleshooting steps.

NOAUTH Authentication required

A Redis server may require a password sent via an AUTH message before commands are accepted. A NOAUTH Authentication required error message suggests the client is not sending a password. GitLab logs may help troubleshoot this error:

  1. Check Workhorse logs in /var/log/gitlab/gitlab-workhorse/current.

  2. If you see messages that look like: 

    2018-11-14_06:18:43.81636 time="2018-11-14T06:18:43Z" level=info msg="redis: dialing" address="redis-server:6379" scheme=rediss
2018-11-14_06:18:43.86929 time="2018-11-14T06:18:43Z" level=error msg="unknown error" error="keywatcher: pubsub receive: NOAUTH Authentication required."

  3. Check that the Redis client password specified in /etc/gitlab/gitlab.rb is correct: 

    gitlab_rails['redis_password'] = 'your-password-here'

  4. If you are using the Omnibus-provided Redis server, check that the server has the same password: 

    redis['password'] = 'your-password-here'

Redis connection reset (ECONNRESET)

If you see Redis::ConnectionError: Connection lost (ECONNRESET) in the GitLab Rails logs (/var/log/gitlab-rails/production.log), this might indicate that the server is expecting SSL but the client is not configured to use it.

  1. Check that the server is actually listening to the port via SSL. For example: 

    /opt/gitlab/embedded/bin/openssl s_client -connect redis-server:6379

  2. Check /var/opt/gitlab/gitlab-rails/etc/resque.yml. You should see something like: 

    production:
  url: rediss://:mypassword@redis-server:6379/

  3. If redis:// is present instead of rediss://, the redis_ssl parameter may not have been configured properly, or the reconfigure step may not have been run.

Connecting to Redis via the CLI

When connecting to Redis for troubleshooting you can use:

  • Redis via Unix domain sockets: 

    /opt/gitlab/embedded/bin/redis-cli -s /var/opt/gitlab/redis/redis.socket

  • Redis via TCP: 

    /opt/gitlab/embedded/bin/redis-cli -h 127.0.0.1 -p 6379

  • Password to authenticate to Redis if required: 

    /opt/gitlab/embedded/bin/redis-cli -h 127.0.0.1 -p 6379 -a <password>