I’m happy to show a simple example I developed for running simple MySQL replication on Kubernetes.
The reason I’ve done this is that I’m in the process of preparing a presentation for Percona Live and decided to start out with basic replication. I figured if I get that working, getting Galera replication using Percona XtraDB Cluster will be even easier since SST makes it easier and less complicated when a node joins the cluster versus a slave connecting to a master and having to concern itself with binary log position and getting a snapshot that corresponds to that.
Using my blog post to easily build a Kubernetes cluster with VMware kubernetes_cluster_vmware all one has to do to use these files is clone the mysql_replication_kubernetes repo
The README in the repo will explain how to run this simple proof-of-concept.
Example
On the master (where I usually create pods, services, replication controllers…) create the master pod and service:
core@master ~/mysql_project $ kubectl create -f mysql-master.json
mysql-master
core@master ~/mysql_project $ kubectl create -f mysql-master-service.json
mysql-master
Create the slave pod and service:
core@master ~/mysql_project $ kubectl create -f mysql-slave.json
mysql-slave
core@master ~/mysql_project $ kubectl create -f mysql-slave-service.json
mysql-slave
Verify things are running:
core@master ~/mysql_project $ kubectl get pods,services
POD IP CONTAINER(S) IMAGE(S) HOST LABELS STATUS
mysql-master 10.244.19.6 mysql-master capttofu/mysql_master_kubernetes:latest 192.168.1.19/192.168.1.19 name=mysql-master Running
mysql-slave 10.244.88.3 mysql capttofu/mysql_slave_kubernetes:latest 192.168.1.21/192.168.1.21 name=mysql-slave Running
NAME LABELS SELECTOR IP PORT
kubernetes component=apiserver,provider=kubernetes <none> 10.100.0.2 443
kubernetes-ro component=apiserver,provider=kubernetes <none> 10.100.0.1 80
mysql-master name=mysql-master name=mysql-master 10.100.154.2 3306
mysql-slave name=mysql-slave name=mysql-slave 10.100.194.208 3306
Connect to the master (see the master-service’s IP). Notice here that the same container that the master is run using is used simply for the MySQL client:
core@node_01 ~ $ docker run -it capttofu/mysql_master_kubernetes mysql -u root -proot -h 10.100.154.2
Welcome to the MySQL monitor. Commands end with ; or <snip>
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> show slave hosts;
+-----------+--------------+------+-----------+--------------------------------------+
| Server_id | Host | Port | Master_id | Slave_UUID |
+-----------+--------------+------+-----------+--------------------------------------+
| 24698 | feec6e4827bc | 3306 | 29002 | dfcb0b0a-d4a6-11e4-b2db-02420af45803 |
+-----------+--------------+------+-----------+--------------------------------------+
1 row in set (0.00 sec)
Connect to the slave:
core@node_01 ~ $ docker run -it capttofu/mysql_master_kubernetes mysql -u root -proot -h 10.100.194.208
<snip>
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> show slave status\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 10.100.154.2
Master_User: repl
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000002
Read_Master_Log_Pos: 2803
Relay_Log_File: mysqld-relay-bin.000003
Relay_Log_Pos: 3015
Relay_Master_Log_File: mysql-bin.000002
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table: mysql.%
Last_Errno: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 2803
Relay_Log_Space: 102663
Until_Condition: None
Until_Log_File:
Until_Log_Pos: 0
Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
Last_IO_Errno: 0
Last_IO_Error:
Last_SQL_Errno: 0
Last_SQL_Error:
Replicate_Ignore_Server_Ids:
Master_Server_Id: 29002
Master_UUID: d79ef03a-d4a6-11e4-b2db-02420af41306
Master_Info_File: /var/lib/mysql/data/master.info
SQL_Delay: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates
Master_Retry_Count: 86400
Master_Bind:
Last_IO_Error_Timestamp:
Last_SQL_Error_Timestamp:
Master_SSL_Crl:
Master_SSL_Crlpath:
Retrieved_Gtid_Set:
Executed_Gtid_Set:
Auto_Position: 0
Replicate_Rewrite_DB:
Channel_Name:
1 row in set (0.01 sec)
Excellent! A master slave setup!
Summary
This is a proof of concept. There is so much more to be done with this example pertaining to regular replication:
- How to add slaves (if replicas for slaves is increased) to the master after the binary log has incremented
- How to automatically perform a slave snapshot/backup and send that to the joining slave
- Volumes…
- Intelligent connection pooling for an application using this setup
Kubernetes is a rapidly developing project and expect many things to change and projects to emerge that solve many of these issues– I may not be aware of something that has already done what my POC here accomplishes. In any case, this should prove to be a useful example for those who are MySQL users who want to acquaint themselves with Kubernetes!