Health Check

Run Command

• How to add RUN instruction when using in-memory Dockerfile.

<build>
    ...
    <runCmds>
        <run>apk add --no-cache curl</run>
    </runCmds>
    <cmd>java -jar maven/${project.name}-${project.version}.jar</cmd>
</build>

• <runCmds> can have multiple <run> tag.
• Here we are installing curl.

Restart Policy

• If you want to restart policies for your images, you can use <restartPolicy> tag.

<run>
    <restartPolicy>
        <name>on-failure</name>
        <retry>3</retry>
    </restartPolicy>
    ...
</run> 

• <restartPolicy> can is added inside of <run> tag.
• It has <name> and <retry> children tag.
• <name> take the type of policy you want to enforce.
• <retry> how many times you want to restart your image, when on-failure policy is used.

Health check

• We can add a health check in our image as well.
• We use <healthCheck> tag, which has few child tags.

<build>
    ...
    <healthCheck>
        <interval>10s</interval>
        <timeout>5s</timeout>
        <startPeriod>10s</startPeriod>
        <retries>3</retry>
        <cmd>curl --fail http://localhost:8080/test/status-5xx || exit 1</cmd>
    </healthCheck>
</build>

• We use <healthCheck> tag inside <build> tag.
• It has few children tags, which represents the option health check supports.
• /test/status-5xx will throw Internal Server Error after 6th request.
• So for time being image will be healthy and after couple of minutes it will be tagged as unhealthy.