Yeebase.Readiness

Package to check the rediness of a flow application.

Useful in a kubernetes readiness and liveness probe to determine if a pod can serve traffic and is alive.

Usage

Readiness

Simply execute the flow command ./flow app:isready.

This will execute all tests defined in the Yeebase.Readiness.testChain of the Settings.yaml. If all tests have passed, the readyChain tasks will be executed.

After a successfully run of the ready chain an internal lock will be set to prevent repeated execution, so only the readyChain will be executed again. The testChain will be executed on every run. So the readyChain should bring your application in an "ready state". Make sure to initialize everything you need. The testChain should ping all services your application depends on.

Liveness

Execute ./flow app:isalive to check if your pod is still alive.

This will execute the Yeebase.Readiness.livenessChain.

Currently the liveness chain is empty by default and has one possible test: statusCode.

Configuration

Add all your tests in the following format in your apps Settings.yaml:

Yeebase:
  Readiness:
    testChain:
      yourUniqueTestKey:
        name: 'Optional name'
        test: 'database' // shorthand for a predefined task in Yeebase\Readiness\Test\*.Test or a full qualified class name
        options:
          key: 'value' // optional options for your test
        position: 'after otherTestKey' // optional position   

After that, the check will execute the ready chain:

Yeebase:
  Readiness:
    readyChain:
      yourUniqueTaskKey:
        name: 'Optional name'
        task: 'command' // shorthand for a predefined task in Yeebase\Readiness\Task\*.Task or a full qualified class name
        options:
          key: 'value' // optional options for your task
        position: 'after otherTaskKey' / optional position
        lockName: 'mylock' // optional lock override. This will create a lock for this task only and ignore the global lock

After a successful ready chain invokation, you can call ./flow app:isalive to execute your liveness chain:

Yeebase:
  Readiness:
    livenessChain:
      yourUniqueTestKey:
        name: 'Optional name'
        task: 'statusCode' // shorthand for a predefined task in Yeebase\Readiness\LivenessTest\*.Test or a full qualified class name
        options:
          key: 'value' // optional options for your task
        position: 'after otherTaskKey' / optional position

Advanced configuration

Before each attempt to execute a ready task, the check will test the Yeebase.Readiness.defaultReadyTaskCondition to see if the task should be executed. In the default configuration this is simply a check to see if the ready lock is not yet set.

You can override this behaviour on a per task basis:

Yeebase:
  Readiness:
    readyChain:
      yourUniqueTaskKey:
        condition: '${Lock.isSet("mylock")}' // this can be any eel expression
        afterInvocation: '${Lock.set("mylock")}' // this will be executed after a successfull invocation

(the lockName setting is simply a shorthand for exactly this example)

To extend the eel context, you can provide additional helpers in Yeebase.Readiness.defaultContext.

Example Configuration

This example could be used in your Flow package to make sure that your application pod has a ready state to serve traffic. Therefore it will always check the ping status for doctrine, redis and beanstalk. On the first run all missing database migrations will be executed, the redis cache flushed and static resources published. After a successfull run only the testChain will be executed again.

Yeebase:
  Readiness:
    testChain:
      database:
        test: doctrine
        position: start
      redis:
        test: redis
        options: 
          hostmane: your-redis-host
      beanstalk:
        test: beanstalk
        options:
          hostname: your-beanstalk-host
    readyChain:
      migrations:
        task: command
        options: 
          command: 'neos.flow:doctrine:migrate'
      flushRedis:
        name: 'Flush redis'
        position: 'start 100'
        task: redis
        options:
          hostname: your-redis-host 
          command: FLUSHDB
          database: 0
      staticResources:
        name: 'Publish static resources'
        task: command
        position: 'end 20' 
        lockname: staticresources
        cacheName: Yeebase_Readiness_LocalLock
        options:
          command: 'neos.flow:resource:publish'
          arguments:
            collection: static
    livenessChain:
      home:
        task: statusCode
        name: 'Homepage responds'
        options:
          url: '/'
          method: 'GET'
          statusCode: 200

Note the lockname configuration. This Configuration enables you to run tasks only once per deployment or always. By default the Yeebase_Readiness_Lock cache is used to read and write locks. Add this to your Caches.yaml and all your application pods will rely on the same lock files as they don't use the local file storage but redis. This will result in a execution once per deployment:

Yeebase_Readiness_Lock:
  backend: Neos\Cache\Backend\RedisBackend
  backendOptions:
    hostname: 'your-redis-server'
    database: 2

The staticResources task has a custom cacheName configured. To ensure that this task will be executed in each application pod set it to local file storage:

Yeebase_Readiness_LocalLock:
  frontend: Neos\Cache\Frontend\StringFrontend
  backend: Neos\Cache\Backend\FileBackend