https://github.com/emahtab/mysql-master-slave-replication
A demo showing MySQL data replication from Master to Slave
https://github.com/emahtab/mysql-master-slave-replication
master-slave-replication mysql replication
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A demo showing MySQL data replication from Master to Slave
- Host: GitHub
- URL: https://github.com/emahtab/mysql-master-slave-replication
- Owner: eMahtab
- Created: 2024-12-05T03:50:27.000Z (over 1 year ago)
- Default Branch: main
- Last Pushed: 2024-12-05T12:49:16.000Z (over 1 year ago)
- Last Synced: 2025-02-02T03:19:09.555Z (over 1 year ago)
- Topics: master-slave-replication, mysql, replication
- Homepage:
- Size: 774 KB
- Stars: 1
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# MySQL Master Slave Replication
**A demo showing MySQL data replication from Master to Slave**, in this example we setup a single master and a single slave or replica.
### !!! Prerequisite : You would need Docker installed on your system to follow along this demo.
# Replication :
Replication enables data from one database server (known as a source or master) to be copied to one or more database servers (known as replicas or slaves).
Replication is usually asynchronous by default; replicas do not need to be connected permanently to receive updates from a source.
## Note : There can be many Replication topologies possible, in this one we setup a single MySQL Master and a single MySQL Slave(Replica). Data is replicated from the master to the slave/replica but not the other way. In Master-Slave topology data is replicated in only one way that is from master to slave/replica.
## Step 1 : Create the Docker compose file and execute docker compose up
Below docker-compose.yml declares two services, named as mysql_master and mysql_slave_1 (in docker compose file actual containers are named as mysql-master and mysql-slave-1). We are using **mysql:8.0** as the docker image, and declare root user password as `toor` and create a test database.
**Make sure docker engine is running on your host machine before running the `docker compose up` command.**
```yml
---
version: "2"
services:
mysql_master:
image: mysql:8.0
container_name: mysql-master
volumes:
- mysql-master-volume:/tmp
command:
[
"mysqld",
"--datadir=/tmp/master/data",
"--log-bin=bin.log",
"--server-id=1"
]
environment:
&mysql-default-environment
MYSQL_ROOT_PASSWORD: toor
MYSQL_DATABASE: test
MYSQL_USER: test_user
MYSQL_PASSWORD: insecure
ports:
- "3308:3306"
mysql_slave_1:
image: mysql:8.0
container_name: mysql-slave-1
volumes:
- mysql-replica1-volume:/tmp
command:
[
"mysqld",
"--datadir=/tmp/slave/data1",
"--log-bin=bin.log",
"--server-id=2"
]
environment: *mysql-default-environment
ports:
- "3309:3306"
volumes:
mysql-master-volume:
mysql-replica1-volume:
```
## Step 2 : Create Replication user on Master with REPLICATION SLAVE privilege
Next we need to create a replication user on Master and grant that user `REPLICATION SLAVE` privilege.
To do this, we execute bash against master **`docker exec -it mysql-master bash`** and connect to mysql **`mysql -uroot -ptoor`** running on master, then execute below mysql commands.
```sql
CREATE USER 'replicator'@'%' IDENTIFIED BY 'rotacilper';
GRANT REPLICATION SLAVE ON *.* TO 'replicator'@'%';
FLUSH PRIVILEGES;
```
Here we create a replication user called `replicator` with password `rotacilper` and grant this user **`REPLICATION SLAVE`** privilege, and finally flush privileges.
## Step 3 : Execute SHOW MASTER STATUS on MySQL Master
Get the master status, execute the command **`SHOW MASTER STATUS;`** on Mysql Master to find the Binlog file and position.
## Step 4 : Connect to MySQL slave and execute CHANGE MASTER TO
Next we need to execute **`CHANGE MASTER TO`** command on MySQL slave. Connect to MySQL slave and execute below command, update MASTER_LOG_FILE and MASTER_LOG_POS values which you get from executing SHOW MASTER STATUS command on MySQL master.
```sql
CHANGE MASTER TO
MASTER_HOST='mysql_master',
MASTER_PORT=3306,
MASTER_USER='replicator',
MASTER_PASSWORD='rotacilper',
MASTER_LOG_FILE='bin.000004',
MASTER_LOG_POS=871,
GET_MASTER_PUBLIC_KEY=1;
```
## Step 5 : Execute START SLAVE on MySQL slave
Execute the command **`START SLAVE;`** on MySQL slave to start the replication, after executing **`START SLAVE;`** you can optionally run **`SHOW REPLICA STATUS;`** to get the status of replica.
One of the most important parameter is **`Seconds_Behind_Source`** which tells how much behind, replica is from master, ideally **`Seconds_Behind_Source`** should always be 0, which means replica is up to date with master.
## Step 6 : See Replication in action
By performing the step 1 to 5, we have set the replication on Slave from Master, now whatever changes are done on master mysql will be replicated to slave automatically.
We create `users` table under test database on the Master and insert records into the users table.
## Step 6a : See Replication in action : update on master database are replicated to slave
We delete 4 users having id as either 3, 7, 9 or 10 on the mysql master.
The changes in mysql master are replicated to mysql replica.
## !Important : Data doesn't replicate from replica to master
**Creating a table on replica and inserting a record**
**Data is not replicated to master in Master-Slave replication**
# References :
1. https://victoronsoftware.com/posts/mysql-master-slave-replication/
2. https://www.youtube.com/watch?v=nMbb1199HQU
3. https://dev.mysql.com/doc/refman/8.4/en/replication.html
4. https://dev.mysql.com/doc/refman/8.4/en/faqs-replication.html