Configuring Load Balancing with HAProxy

Percona Operator for MySQL based on Percona XtraDB Cluster provides a choice of two cluster components to provide load balancing and proxy service: you can use either HAProxy or ProxySQL . You can control which one to use, if any, by enabling or disabling via the haproxy.enabled and proxysql.enabled options in the deploy/cr.yaml configuration file.

Use the following command to enable HAProxy:

$ kubectl patch pxc cluster1 --type=merge --patch '{
  "spec": {
     "haproxy": {
        "enabled": true,
        "size": 3,
        "image": "percona/percona-xtradb-cluster-operator:1.15.0-haproxy" },
     "proxysql": { "enabled": false }
  }}'

Warning

Switching from ProxySQL to HAProxy will cause Percona XtraDB Cluster Pods restart. Switching from HAProxy to ProxySQL is not possible, and if you need ProxySQL, this should be configured at cluster creation time.

The resulting HAPproxy setup normally contains two services:

• cluster1-haproxy service listening on ports 3306 (MySQL) and 3309 (the proxy protocol useful for operations such as asynchronous calls). This service is pointing to the number zero Percona XtraDB Cluster member (cluster1-pxc-0) by default when this member is available. If a zero member is not available, members are selected in descending order of their numbers (e.g. cluster1-pxc-2, then cluster1-pxc-1, etc.). This service 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.

  haproxy.exposePrimary.enabled Custom Resource option enables or disables cluster1-haproxy service.

• cluster1-haproxy-replicas listening on port 3306 (MySQL). This service selects Percona XtraDB Cluster members to serve queries following the Round Robin load balancing algorithm. It should not be used for write requests.

  haproxy.exposeReplicas.enabled Custom Resource option enables or disables cluster1-haproxy-replicas service (on by default).

Note

If you need to configure cluster1-haproxy and cluster1-haproxy-replicas as a headless Service (e.g. to use on the tenant network), add the following annotation in the Custom Resource metadata section of the deploy/cr.yaml:

yaml apiVersion: pxc.percona.com/v1 kind: PerconaXtraDBCluster metadata: name: cluster1 annotations: percona.com/headless-service: true ...

This annotation works only at service creation time and can’t be added later.

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 XtraDB Cluster member becomes synced, and then proceeds to upgrade the next member. When the upgrade is finished for all the readers, then the writer Percona XtraDB Cluster member is finally upgraded.

Passing custom configuration options to HAProxy

You can pass custom configuration to HAProxy in one of the following ways:

• edit the deploy/cr.yaml file,
• use a ConfigMap,
• use a Secret object.

Note

If you specify a custom HAProxy configuration in this way, the Operator doesn’t provide its own HAProxy configuration file except several hardcoded options (which therefore can’t be overwritten). That’s why you should specify either a full set of configuration options or nothing. Additionally, when upgrading Percona XtraDB Cluster it would be wise to check the HAProxy configuration file provided by the Operator and make sure that your custom config is still compatible with the new variant.

Edit the deploy/cr.yaml file

You can add options from the haproxy.cfg configuration file by editing haproxy.configuration key in the deploy/cr.yaml file. Here is an example:

...
haproxy:
    enabled: true
    size: 3
    image: percona/percona-xtradb-cluster-operator:1.15.0-haproxy
    configuration: |
      global
        maxconn 2048
        external-check
        stats socket /var/run/haproxy.sock mode 600 expose-fd listeners level user
      defaults
        log global
        mode tcp
        retries 10
        timeout client 10000
        timeout connect 100500
        timeout server 10000
      frontend galera-in
        bind *:3309 accept-proxy
        bind *:3306
        mode tcp
        option clitcpka
        default_backend galera-nodes
      frontend galera-replica-in
        bind *:3309 accept-proxy
        bind *:3307
        mode tcp
        option clitcpka
        default_backend galera-replica-nodes

Use a ConfigMap

You can use a configmap and the cluster restart to reset configuration options. A configmap allows Kubernetes to pass or update configuration data inside a containerized application.

Use the kubectl command to create the configmap from external resources, for more information see Configure a Pod to use a ConfigMap .

For example, you define a haproxy.cfg configuration file with the following setting:

global
  maxconn 2048
  external-check
  stats socket /var/run/haproxy.sock mode 600 expose-fd listeners level user
defaults
  log global
  mode tcp
  retries 10
  timeout client 10000
  timeout connect 100500
  timeout server 10000
frontend galera-in
  bind *:3309 accept-proxy
  bind *:3306
  mode tcp
  option clitcpka
  default_backend galera-nodes
frontend galera-replica-in
  bind *:3309 accept-proxy
  bind *:3307
  mode tcp
  option clitcpka
  default_backend galera-replica-nodes

You can create a configmap from the haproxy.cfg file with the kubectl create configmap command.

You should use the combination of the cluster name with the -haproxy suffix as the naming convention for the configmap. To find the cluster name, you can use the following command:

$ kubectl get pxc

The syntax for kubectl create configmap command is:

kubectl create configmap <cluster-name>-haproxy <resource-type=resource-name>

The following example defines cluster1-haproxy as the configmap name and the haproxy.cfg file as the data source:

$ kubectl create configmap cluster1-haproxy --from-file=haproxy.cfg

To view the created configmap, use the following command:

$ kubectl describe configmaps cluster1-haproxy

Use a Secret Object

The Operator can also store configuration options in Kubernetes Secrets . This can be useful if you need additional protection for some sensitive data.

You should create a Secret object with a specific name, composed of your cluster name and the haproxy suffix.

Note

To find the cluster name, you can use the following command:

$ kubectl get pxc

Configuration options should be put inside a specific key inside of the data section. The name of this key is haproxy.cfg for ProxySQL Pods.

Actual options should be encoded with Base64 .

For example, let’s define a haproxy.cfg configuration file and put there options we used in the previous example:

global
  maxconn 2048
  external-check
  stats socket /var/run/haproxy.sock mode 600 expose-fd listeners level user
defaults
  log global
  mode tcp
  retries 10
  timeout client 10000
  timeout connect 100500
  timeout server 10000
frontend galera-in
  bind *:3309 accept-proxy
  bind *:3306
  mode tcp
  option clitcpka
  default_backend galera-nodes
frontend galera-replica-in
  bind *:3309 accept-proxy
  bind *:3307
  mode tcp
  option clitcpka
  default_backend galera-replica-nodes

You can get a Base64 encoded string from your options via the command line as follows:

in Linuxin macOS

$ cat haproxy.cfg | base64 --wrap=0

$ cat haproxy.cfg | base64

Note

Similarly, you can read the list of options from a Base64 encoded string:

$ echo "IGdsb2JhbAogICBtYXhjb25uIDIwNDgKICAgZXh0ZXJuYWwtY2hlY2sKICAgc3RhdHMgc29ja2V0\
  IC92YXIvcnVuL2hhcHJveHkuc29jayBtb2RlIDYwMCBleHBvc2UtZmQgbGlzdGVuZXJzIGxldmVs\
  IHVzZXIKIGRlZmF1bHRzCiAgIGxvZyBnbG9iYWwKICAgbW9kZSB0Y3AKICAgcmV0cmllcyAxMAog\
  ICB0aW1lb3V0IGNsaWVudCAxMDAwMAogICB0aW1lb3V0IGNvbm5lY3QgMTAwNTAwCiAgIHRpbWVv\
  dXQgc2VydmVyIDEwMDAwCiBmcm9udGVuZCBnYWxlcmEtaW4KICAgYmluZCAqOjMzMDkgYWNjZXB0\
  LXByb3h5CiAgIGJpbmQgKjozMzA2CiAgIG1vZGUgdGNwCiAgIG9wdGlvbiBjbGl0Y3BrYQogICBk\
  ZWZhdWx0X2JhY2tlbmQgZ2FsZXJhLW5vZGVzCiBmcm9udGVuZCBnYWxlcmEtcmVwbGljYS1pbgog\
  ICBiaW5kICo6MzMwOSBhY2NlcHQtcHJveHkKICAgYmluZCAqOjMzMDcKICAgbW9kZSB0Y3AKICAg\
  b3B0aW9uIGNsaXRjcGthCiAgIGRlZmF1bHRfYmFja2VuZCBnYWxlcmEtcmVwbGljYS1ub2Rlcwo=" | base64 --decode

Finally, use a yaml file to create the Secret object. For example, you can create a deploy/my-haproxy-secret.yaml file with the following contents:

apiVersion: v1
kind: Secret
metadata:
  name: cluster1-haproxy
data:
  haproxy.cfg: "IGdsb2JhbAogICBtYXhjb25uIDIwNDgKICAgZXh0ZXJuYWwtY2hlY2sKICAgc3RhdHMgc29ja2V0\
     IC92YXIvcnVuL2hhcHJveHkuc29jayBtb2RlIDYwMCBleHBvc2UtZmQgbGlzdGVuZXJzIGxldmVs\
     IHVzZXIKIGRlZmF1bHRzCiAgIGxvZyBnbG9iYWwKICAgbW9kZSB0Y3AKICAgcmV0cmllcyAxMAog\
     ICB0aW1lb3V0IGNsaWVudCAxMDAwMAogICB0aW1lb3V0IGNvbm5lY3QgMTAwNTAwCiAgIHRpbWVv\
     dXQgc2VydmVyIDEwMDAwCiBmcm9udGVuZCBnYWxlcmEtaW4KICAgYmluZCAqOjMzMDkgYWNjZXB0\
     LXByb3h5CiAgIGJpbmQgKjozMzA2CiAgIG1vZGUgdGNwCiAgIG9wdGlvbiBjbGl0Y3BrYQogICBk\
     ZWZhdWx0X2JhY2tlbmQgZ2FsZXJhLW5vZGVzCiBmcm9udGVuZCBnYWxlcmEtcmVwbGljYS1pbgog\
     ICBiaW5kICo6MzMwOSBhY2NlcHQtcHJveHkKICAgYmluZCAqOjMzMDcKICAgbW9kZSB0Y3AKICAg\
     b3B0aW9uIGNsaXRjcGthCiAgIGRlZmF1bHRfYmFja2VuZCBnYWxlcmEtcmVwbGljYS1ub2Rlcwo="

When ready, apply it with the following command:

$ kubectl create -f deploy/my-haproxy-secret.yaml

Note

Do not forget to restart Percona XtraDB Cluster to ensure the cluster has updated the configuration.

Enabling the Proxy protocol

The Proxy protocol allows HAProxy to provide a real client address to Percona XtraDB Cluster.

Note

To use this feature, you should have a Percona XtraDB Cluster image version 8.0.21 or newer.

Normally Proxy protocol is disabled, and Percona XtraDB Cluster sees the IP address of the proxying server (HAProxy) instead of the real client address. But there are scenarios when making real client IP-address visible for Percona XtraDB Cluster is important: e.g. it allows to have privilege grants based on client/application address, and significantly enhance auditing.

You can enable Proxy protocol on Percona XtraDB Cluster by adding proxy_protocol_networks option to pxc.configuration key in the deploy/cr.yaml configuration file.

Note

Depending on the load balancer of your cloud provider, you may also need setting haproxy.externaltrafficpolicy option in deploy/cr.yaml.

More information about Proxy protocol can be found in the official HAProxy documentation .

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Last update: 2024-08-26