Dockerized GitLab, Redis, and Redis Sentinel
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README.md

special-happiness

Dockerized GitLab, Redis, and Redis Sentinel.

Overview

This docker-compose will setup GitLab 9 CE, Redis, Redis Sentinel, and MailHog. It also allows for bringing up slave Redis/Sentinel containers.

GitLab is configured to use Redis Sentinel to failover to one of the slave Redis containers in the event the current master fails.

Usage

These instructions presume you already have Docker and docker-compose installed on your machine.

Download the source code for this repository or clone the project.

From the project's root directory, start everything with docker-compose up.

docker-compose up

After a time, you should see happy little GitLab messages and can visit the application in your browser.

GitLab will be available in your browser at http://localhost:8082. You should be presented with setting the root user's password.

Login with the username root and whatever password you selected.

Starting additional Redis containers

Use docker-compose scale to start as many slave Redis containers as you like.

For example, to start four (4) Redis slaves, run:

docker-compose scale redis-slave=4

Testing Redis Sentinel

The simplest way to see what Sentinel is up to is to start a shell on one of the Redis containers and then connect to Sentinel using redis-cli and the INFO command.

$ docker exec -it specialhappiness_redis-master_1 /bin/bash
root@979a3c28b39e:/data# redis-cli -p 26379
127.0.0.1:26379> INFO
#.... some output
master0:name=mymaster,status=ok,address=172.18.0.3:6379,slaves=4,sentinels=5

Testing Redis failover

After you've verified Sentinel is working, you can test failover by killing the master, or by using Redis's DEBUG sleep command.

docker exec -t specialhappiness_redis-master_1 redis-cli -p 6379 DEBUG sleep 30

After a few seconds, your console should light up with activity from the Redis containers. You can verify that the master changed by running the INFO command on one of the Redis Sentinel instances.

Testing GitLab failover

Follow the steps outlined above, then look for some output from the gitlab container regarding the failover.

# ... lots more stacks
gitlab_1        | 2017-10-25_03:55:25.96920 2017-10-25T03:55:25.967Z 746 TID-ow9t2ls3c ERROR: /opt/gitlab/embedded/lib/ruby/gems/2.3.0/gems/sidekiq-5.0.4/lib/sidekiq.rb:92:in `redis'
gitlab_1        | 2017-10-25_03:55:25.96921 2017-10-25T03:55:25.967Z 746 TID-ow9t2ls3c ERROR: /opt/gitlab/embedded/lib/ruby/gems/2.3.0/gems/sidekiq-5.0.4/lib/sidekiq/fetch.rb:36:in `retrieve_work'
gitlab_1        | 2017-10-25_03:55:25.96931 2017-10-25T03:55:25.967Z 746 TID-ow9t2ls3c ERROR: /opt/gitlab/embedded/lib/ruby/gems/2.3.0/gems/sidekiq-5.0.4/lib/sidekiq/processor.rb:91:in `get_one'
gitlab_1        | 2017-10-25_03:55:25.96938 2017-10-25T03:55:25.967Z 746 TID-ow9t2ls3c ERROR: /opt/gitlab/embedded/lib/ruby/gems/2.3.0/gems/sidekiq-5.0.4/lib/sidekiq/processor.rb:101:in `fetch'
gitlab_1        | 2017-10-25_03:55:25.96942 2017-10-25T03:55:25.968Z 746 TID-ow9t2ls3c ERROR: /opt/gitlab/embedded/lib/ruby/gems/2.3.0/gems/sidekiq-5.0.4/lib/sidekiq/processor.rb:84:in `process_one'
gitlab_1        | 2017-10-25_03:55:25.96945 2017-10-25T03:55:25.968Z 746 TID-ow9t2ls3c ERROR: /opt/gitlab/embedded/lib/ruby/gems/2.3.0/gems/sidekiq-5.0.4/lib/sidekiq/processor.rb:73:in `run'
gitlab_1        | 2017-10-25_03:55:25.96952 2017-10-25T03:55:25.968Z 746 TID-ow9t2ls3c ERROR: /opt/gitlab/embedded/lib/ruby/gems/2.3.0/gems/sidekiq-5.0.4/lib/sidekiq/util.rb:16:in `watchdog'
gitlab_1        | 2017-10-25_03:55:25.96964 2017-10-25T03:55:25.968Z 746 TID-ow9t2ls3c ERROR: /opt/gitlab/embedded/lib/ruby/gems/2.3.0/gems/sidekiq-5.0.4/lib/sidekiq/util.rb:25:in `block in safe_thread'
redis-slave_2   | 10:X 25 Oct 03:55:26.385 # +sdown slave 172.18.0.3:6379 172.18.0.3 6379 @ mymaster 172.18.0.4 6379
redis-slave_3   | 9:X 25 Oct 03:55:26.454 # +sdown slave 172.18.0.3:6379 172.18.0.3 6379 @ mymaster 172.18.0.4 6379
redis-slave_4   | 10:X 25 Oct 03:55:26.412 # +sdown slave 172.18.0.3:6379 172.18.0.3 6379 @ mymaster 172.18.0.4 6379
redis-slave_1   | 10:X 25 Oct 03:55:26.443 # +sdown slave 172.18.0.3:6379 172.18.0.3 6379 @ mymaster 172.18.0.4 6379
gitlab_1        | 2017-10-25_03:55:28.04403 2017-10-25T03:55:28.043Z 746 TID-ow9t2lsk0 INFO: Redis is online, 3.495915106 sec downtime
gitlab_1        | 2017-10-25_03:55:28.24597 2017-10-25T03:55:28.245Z 746 TID-ow9t2lb7k INFO: Redis is online, 3.49493719 sec downtime
# ...

Cleaning up

Run docker-compose down to turn off and delete all of the containers that were started.

docker-compose down

Notes

GitHub suggested the name, and I liked it.

Special thanks to Aeolun for the original contribution this is based on.