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Configuring Load Balancing with HAProxy

Percona Operator for MySQL provides load balancing and proxy service with HAProxy (enabled by default). HAProxy is the only solution proxy when asynchronous replication between MySQL instances is enabled, while group replication can be used either with HAProxy or MySQL Router. You can control whether to use HAProxy or not by enabling or disabling it via the haproxy.enabled option in the deploy/cr.yaml configuration file.

Note

When enabling HAProxy, make sure MySQL Router is disabled (proxy.router.enabled option should be set to false).

For example, you can use the following command to enable HAProxy for existing cluster:

$ kubectl patch ps cluster1 --type=merge --patch '{
  "spec": {
     "proxy": {
       "haproxy": {
          "enabled": true,
          "size": 3,
          "image": "percona/haproxy:2.8.5" }
       "router": {
          "enabled": false }
       }
  }}'

The resulting HAPproxy setup will contain the cluster1-haproxy service listening on ports 3306 (MySQL cluster zero member) and 3307 (other members).

This service is pointing to the MySQL cluster member number zero (cluster1-mysql-0) on the default 3306 port when this member is available. If a zero member is not available, members are selected in descending order of their numbers (e.g. cluster1-mysql-2, then cluster1-mysql-1, etc.). It can be used for both read and write load, or it can also be used just for write load (single writer mode) in setups with split write and read loads. On 3307 port this service selects MySQL cluster members to serve queries following the Round Robin load balancing algorithm.

When the cluster with HAProxy is upgraded, the following steps take place. First, reader members are upgraded one by one: the Operator waits until the upgraded Percona Distribution for MySQL cluster member becomes synced, and then proceeds to upgrade the next member. When the upgrade is finished for all the readers, then the writer MySQL cluster member is finally upgraded.

Passing custom configuration options to HAProxy

You can pass custom configuration to HAProxy, adding options from the haproxy.cfg configuration file to the haproxy.configuration Custom Resource option in the deploy/cr.yaml file. Here is an example:

...
haproxy:
  enabled: true
  size: 3
  image: perconalab/percona-xtradb-cluster-operator:0.7.0-haproxy
  configuration: |
    global
      maxconn 2048
      external-check
      insecure-fork-wanted
      stats socket /var/run/haproxy.sock mode 600 expose-fd listeners level admin
    defaults
      default-server init-addr last,libc,none
      log global
      mode tcp
      retries 10
      timeout client 28800s
      timeout connect 100500
      timeout server 28800s
    frontend mysql-primary-in
      bind *:3309 accept-proxy
      bind *:3306
      mode tcp
      option clitcpka
      default_backend mysql-primary
    frontend mysql-replicas-in
      bind *:3307
      mode tcp
      option clitcpka
      default_backend mysql-replicas
    frontend stats
      bind *:8404
      mode http
      http-request use-service prometheus-exporter if { path /metrics }

the actual default configuration file can be found here .

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Last update: 2024-05-02