[FLINK-27329] Add default value of replica of JM pod and not declare it in example yamls

• Type: Improvement
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Fix Version/s: kubernetes-operator-1.0.0
• Component/s: Kubernetes Operator
• Assignee: Biao Geng
• Reporter: Biao Geng
• Created: 20/Apr/22 14:14
• Updated: 12/May/22 07:49
• Resolved: 12/May/22 07:49

Description

Currently, we do not explicitly set the default value of `replica` in `JobManagerSpec`. As a result, Java sets the default value to be zero.
Besides, in our examples, we explicitly declare `replica` in `JobManagerSpec` to be 1.
After a deeper look when debugging the exception thrown in FLINK-27310, we find it would be better to set the default value to 1 for the `replica` field and remove the declaration in examples due to following reasons:
1. A normal Session or Application cluster should have at least one JM. The current default value, zero, does not follow the common case.
2. One JM can work for k8s HA mode as well and if users really want to launch a standby JM for faster recorvery, they can declare the value of `replica` field in the yaml file. In examples, we just use the new default value(i.e. 1), which should be fine.