Support for initContainers to wait for database startup

[Sonny78]

On first installing my resources I get sometimes the following exception in my camunda pod:

06-Oct-2021 14:21:56.462 SEVERE [main] org.postgresql.Driver.connect Connection error: 
	org.postgresql.util.PSQLException: FATAL: the database system is starting up

or even:

7-Oct-2021 09:58:29.075 SEVERE [main] org.postgresql.Driver.connect Connection error: 
	org.postgresql.util.PSQLException: Connection to db-cluster:5432 refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections.
		at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:265)
		at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:49)

To avoid this I want to use initcontainers, which wait until the service and database are started.

initContainers:
  - name: check-db-service-available
    image: busybox:1.34.0
    command: ['sh', '-c', 
      'until nslookup db-cluster; 
      do echo waiting for db-cluster; sleep 2; done; 
      echo db service found;']
  - name: check-db-ready
    image: postgres:13.4
    command: ['sh', '-c', 
    'until pg_isready -h db-cluster -d processEngine -p 5432; 
      do echo waiting for database; sleep 2; done; 
      echo database is ready']

Does this make sense for you? I tried it directly with the yaml files without using the helm chart and it worked quite well. But of cause I want rather to use your helm charts.

Perhaps it could be an option to include something like this in the development yaml:

{{- if .Values.initContainers }}
  {{- toYaml .Values.initContainers | nindent 6 }}
{{- end }}

So that I will be able to define my initContainers in the values file

[aabouzaid]

@Sonny78 Thanks for your suggestion 👏

In v1.3.0 it's possible to define any initContainers.

[Sonny78]

Thanks, works fine.