MySQL Replication Master/Slave cluster example
One of the most common feature requested for the MySQL docker official image is adding replication master/slave ability. As docker-library/mysql#43 is closed by deciding that it's a feature should be implemented via
init script, my example here is a demo of how to do it.
The official MySQL image have the customize ability by running script files under
/docker-entrypoint-initdb.d/ directory. The script has to be either a shell script,
.sh, or a SQL script,
To implement the MySQL replication, I borrowed the code from PR: docker-library/mysql#43, modified and saved as
replica.sh. As described in the script comments, we have 5 more special environment variables for replication.
MYSQL_REPLICA_USER: create the given user on the intended master host
MYSQL_MASTER_SERVER: change master on this location on the intended slave
MYSQL_MASTER_PORT: optional, by default 3306
MYSQL_MASTER_WAIT_TIME: seconds to wait for the master to come up
Dockerfile is very simple, just copied
/docker-entrypoint-initdb.d/ directory. That's it.
The reason why I create a new Docker image here, instead of mount the file directly into container during the runtime, is that, it's not easy to maintain the updated file across the cluster. Put it into the Docker image is best way to handle such static config file in cluster environment.
To build the image just:
docker build -t twang2218/mysql:5.7-replica .
twang2218 with your docker username
Then push the image to the Docker Hub, so it can be used across cluster.
docker push twang2218/mysql:5.7-replica
Then, let's use the new MySQL image with replication ability. To do that, I created a simple
version: '2' services: master: image: twang2218/mysql:5.7-replica restart: unless-stopped ports: - 3306:3306 environment: - MYSQL_ROOT_PASSWORD=master_passw0rd - MYSQL_REPLICA_USER=replica - MYSQL_REPLICA_PASS=replica_Passw0rd command: ["mysqld", "--log-bin=mysql-bin", "--server-id=1"] slave: image: twang2218/mysql:5.7-replica restart: unless-stopped ports: - 3307:3306 environment: - MYSQL_ROOT_PASSWORD=slave_passw0rd - MYSQL_REPLICA_USER=replica - MYSQL_REPLICA_PASS=replica_Passw0rd - MYSQL_MASTER_SERVER=master - MYSQL_MASTER_WAIT_TIME=10 command: ["mysqld", "--log-bin=mysql-bin", "--server-id=2"]
Then, just simply run it by
docker-compose up -d, then our MySQL replication master and slave are running. Feel free to create something on the master and check whether it's been replicated to the slave.