Configuring Different Types of Hooks

In this guide, we are going to discuss how to configure different types of hooks in HookTemplate. Here, we will give some examples of different configurations.

Based on Action

Based on action of a hook, we can configure them for the following use cases.

HTTPGet

httpGet hook allows sending an HTTP GET request to an HTTP server before and after the backup/restore process. The following configurable fields are available for httpGet hook.

Examples:

• Hook with host and port are specified:

action:
  httpGet:
    host: my-host.demo.svc
    port: 8080
    path: "/"
    scheme: HTTP

• Hook to extract host and port from the hook executor pod:

action:
  httpGet:
    port: my-port
    path: "/"
    scheme: HTTP
  containerName: my-container

• Hook for sending custom header in the HTTP request:

action:
  httpGet:
    host: my-host.demo.svc
    port: 8080
    path: "/"
    scheme: HTTP
    httpHeaders:
    - name: "User-Agent"
      value: "kubestash/0.5.x"

HTTPPost

httpPost hook allows sending an HTTP POST request to an HTTP server before and after the backup/restore process. The following configurable fields are available for httpPost hook.

Examples:

• Send JSON data in the request body:

action:
  httpPost:
    host: my-service.mynamespace.svc
    path: /demo
    port: 8080
    scheme: HTTP
    httpHeaders:
    - name: Content-Type
      value: application/json
    body: '{
            "name": "john doe",
            "age": "28"
           }'

• Send URL encoded form in the request:

action:
  httpPost:
    host: my-service.mynamespace.svc
    path: /demo
    port: 8080
    scheme: HTTP
    form:
    - key: "name"
      values: ["john doe"]
    - key: "age"
      values: ["28"]

TCPSocket

tcpSocket hook allows running a check against a TCP port to verify whether it is open or not. The following configurable fields are available for tcpSocket hook.

Examples:

• Hook with host and port field specified.

action:
  tcpSocket:
    host: my-host.demo.svc
    port: 8080

• Hook to extract host and port from the hook executor pod.

action:
  tcpSocket:
    port: my-port
  containerName: my-container

Exec

exec hook allows running commands inside a container before or after the backup/restore process. The following configurable fields are available for exec hook.

If you don’t specify containerName for exec hook, the command will be executed into the 0th container of the respective pod.

Examples:

• Hook to remove old corrupted data:

action:
  exec:
    command: ["/bin/sh","-c","rm -rf /corrupted/data/directory"]
  containerName: my-container

• Hook to make a MySQL database read-only:

action:
  exec:
    command:
      - /bin/sh
      - -c
      - mysql -u root --password=$MYSQL_ROOT_PASSWORD -e "SET GLOBAL super_read_only = ON;"
  containerName: mysql

• Hook to make a MySQL database writable:

action:
  exec:
    command:
      - /bin/sh
      - -c
      - mysql -u root --password=$MYSQL_ROOT_PASSWORD -e "SET GLOBAL super_read_only = OFF;"
  containerName: mysql

• Hook to remove corrupted MySQL database:

action:
  exec:
    command:
      - /bin/sh
      - -c
      - mysql -u root --password=$MYSQL_ROOT_PASSWORD -e "DROP DATABASE companyRecord;"
  containerName: mysql

• Hook to apply some migration after restoring a MySQL database:

action:
  exec:
    command:
      - /bin/sh
      - -c
      - mysql -u root --password=$MYSQL_ROOT_PASSWORD -e "RENAME TABLE companyRecord.employee TO companyRecord.salaryRecord;"
  containerName: mysql

Based on Executor

Based on executor of a hook, we can configure them in the following ways.

Pod Executor

Provide list of key value pair that will be used as label selector to select the desired pods. You can use comma to separate multiple labels (i.e. "app=my-app,env=prod").

Examples:

• Execute hook on all the selected pods (only filtered by selector):

executor:
  type: Pod
  pod:
    selector: env=dev, app=web
    strategy: ExecuteOnAll

• Execute hook on only one of the selected pods (only filtered by selector). This is default behavior:

executor:
  type: Pod
  pod:
    selector: env=dev, app=web

• Execute hook on all the selected pods (filtered by selector and owner):

executor:
  type: Pod
  pod:
    selector: env=dev, app=web
    owner:
      apiVersion: apps/v1
      kind: Deployment
      name: kubestash-op
    strategy: ExecuteOnAll

Operator Executor

KubeStash operator itself will execute the hook.

Example:

executor:
  type: Operator

Function Executor

Hook is executed by a Job. We need to create a Function and refer it in FunctionHookExecutorSpec. This Function will be used to create the hook executor job.

Example:

executor:
  type: Function
  function:
    name: hook-function

Here we can provide a list of environment variables that will be passed to the executor container. We can also provide volumes and the volumes mounts for the executor container.

If the above hooks do not cover your use cases, or you have any questions regarding the hooks, please feel free to open an issue here.