Reload namespace and label filtering

By default, a namespace chosen using the steps outlined in Namespace resolution will be used to listen to changes in configmaps and secrets. i.e.: if you do not tell reload what namespaces and configmaps/secrets to watch for, it will watch all configmaps/secrets from the namespace that will be computed using the above algorithm.

On the other hand, you can define a more fine-grained approach. For example, you can specify the namespaces where changes will be monitored:

spring:
  application:
    name: event-reload
  cloud:
    kubernetes:
      reload:
        enabled: true
        strategy: shutdown
        mode: event
        namespaces:
          - my-namespace

Such a configuration will make the app watch changes only in the my-namespace namespace. Mind that this will watch all configmaps/secrets (depending on which one you enable). If you want an even more fine-grained approach, you can enable "label-filtering". First we need to enable such support via : enable-reload-filtering: true

spring:
  application:
    name: event-reload
  cloud:
    kubernetes:
      reload:
        enabled: true
        strategy: shutdown
        mode: event
        namespaces:
          - my-namespaces
        monitoring-config-maps: true
        enable-reload-filtering: true

What this will do, is watch configmaps/secrets that only have the spring.cloud.kubernetes.config.informer.enabled: true label.

Table 1. Properties:
Name	Type	Default	Description
`spring.cloud.kubernetes.reload.enabled`	`Boolean`	`false`	Enables monitoring of property sources and configuration reload
`spring.cloud.kubernetes.reload.monitoring-config-maps`	`Boolean`	`true`	Allow monitoring changes in config maps
`spring.cloud.kubernetes.reload.monitoring-secrets`	`Boolean`	`false`	Allow monitoring changes in secrets
`spring.cloud.kubernetes.reload.strategy`	`Enum`	`refresh`	The strategy to use when firing a reload (`refresh`, `restart_context`, or `shutdown`)
`spring.cloud.kubernetes.reload.mode`	`Enum`	`event`	Specifies how to listen for changes in property sources (`event` or `polling`)
`spring.cloud.kubernetes.reload.period`	`Duration`	`15s`	The period for verifying changes when using the `polling` strategy
`spring.cloud.kubernetes.reload.namespaces`	`String[]`		namespaces where we should watch for changes
`spring.cloud.kubernetes.reload.enable-reload-filtering`	`String`		enabled labeled filtering for reload functionality

Notes:

You should not use properties under spring.cloud.kubernetes.reload in config maps or secrets. Changing such properties at runtime may lead to unexpected results.
Deleting a property or the whole config map does not restore the original state of the beans when you use the refresh level.