Redis-Cluster-With-Sentinel

Redis cluster with Docker Compose

Getting Started

These instructions will get you a copy of the project up and running on your local machine for development purposes. See running for notes on how to run the project on a system.

Prerequisites

1. Clone the project to your local environment:

   git clone https://github.com/ankitrajput0096/Redis-Cluster-With-Sentinels
   

2. You need Docker to be installed:

   Windows:

   https://download.docker.com/win/stable/Docker%20for%20Windows%20Installer.exe

   Mac:

   https://download.docker.com/mac/stable/Docker.dmg

   Ubuntu:

   https://docs.docker.com/install/linux/docker-ce/ubuntu/

Redis Cluster Configurations Details

There are following services in the cluster,

• master: Master Redis Server
• slave: Slave Redis Server
• sentinel: Sentinel Server

The sentinels are configured with a "mymaster" instance with the following properties -

sentinel monitor mymaster redis-master 6379 2
sentinel down-after-milliseconds mymaster 5000
sentinel parallel-syncs mymaster 1
sentinel failover-timeout mymaster 5000

The details could be found in sentinel/sentinel.conf

The default values of the environment variables for Sentinel are as following

• SENTINEL_QUORUM: 2
• SENTINEL_DOWN_AFTER: 5000
• SENTINEL_FAILOVER: 5000

Installing and Running

Build services

docker-compose build

running services

docker-compose up

Check the status of redis cluster

docker-compose ps

The result is

          Name                        Command               State                 Ports               
------------------------------------------------------------------------------------------------------
redis_cluster_master_1     docker-entrypoint.sh redis ...   Up      6379/tcp                          
redis_cluster_sentinel_1   entrypoint.sh                    Up      0.0.0.0:10001->26379/tcp, 6379/tcp
redis_cluster_slave_1      docker-entrypoint.sh redis ...   Up      6379/tcp  

NOTE : Refer the below configuration of cluster as SENTINEL_QUORUM value is 2.

Scale out the instance number of sentinel and number of slaves/Replica

docker-compose up --scale sentinel=3 --scale slave=4

Check the status of redis cluster

docker-compose ps

The result is

          Name                        Command               State                 Ports               
------------------------------------------------------------------------------------------------------
redis_cluster_master_1     docker-entrypoint.sh redis ...   Up      6379/tcp                          
redis_cluster_sentinel_1   entrypoint.sh                    Up      0.0.0.0:10001->26379/tcp, 6379/tcp
redis_cluster_sentinel_2   entrypoint.sh                    Up      0.0.0.0:10002->26379/tcp, 6379/tcp
redis_cluster_sentinel_3   entrypoint.sh                    Up      0.0.0.0:10003->26379/tcp, 6379/tcp
redis_cluster_slave_1      docker-entrypoint.sh redis ...   Up      6379/tcp                          
redis_cluster_slave_2      docker-entrypoint.sh redis ...   Up      6379/tcp                          
redis_cluster_slave_3      docker-entrypoint.sh redis ...   Up      6379/tcp                          
redis_cluster_slave_4      docker-entrypoint.sh redis ...   Up      6379/tcp  

For pausing master redis server.

docker-compose pause master

For unpausing master redis server.

docker-compose unpause master

And get the sentinel infomation with following commands

redis-cli -p 10001 -h 127.0.0.1 sentinel get-master-addr-by-name mymaster

Getting all required information from redis sentinels about this redis cluster

NOTE: To run all the below commands, install redis-tools in your terminal using -> sudo apt install redis-tools

Command	Description
redis-cli -p 10001 -h 127.0.0.1 sentinel masters	Show a list of all monitored masters + state
redis-cli -p 10001 -h 127.0.0.1 sentinel master mymaster	Show the state of a specified master
redis-cli -p 10001 -h 127.0.0.1 sentinel slaves mymaster	Show the slaves of the master + state
redis-cli -p 10001 -h 127.0.0.1 sentinel sentinels mymaster	Show the Sentinel instances for this master + state
redis-cli -p 10001 -h 127.0.0.1 sentinel get-master-addr-by-name mymaster	Return ip and port of the master. While a failover is in progress the ip and port of the promoted slave are returned
redis-cli -p 10001 -h 127.0.0.1 sentinel reset mymaster	Reset the masters with a matching name. Clears previous state for the master, removes every slave and sentinel discovered. A fresh discovery is started.
redis-cli -p 10001 -h 127.0.0.1 sentinel failover mymaster	Force a failover, as if the master was not reachable
redis-cli -p 10001 -h 127.0.0.1 sentinel ckquorum mymaster	Check if the current Sentinel configuration is able to reach quorum and majority
redis-cli -p 10001 -h 127.0.0.1 sentinel flushconfig	Force Sentinel to rewrite it's configuration on disk
redis-cli -p 10001 -h 127.0.0.1 sentinel remove mymaster	Remove a specified master from monitoring

Built With

• Docker - For containerization of application
• Redis - For Redis
• Redis Sentinel - For Redis Sentinel

Contributing

If you have any improvement suggestions please create a pull request and I'll review it.

Authors

• Ankit Rajput - Initial work - Github

License

This project is licensed under the MIT License