Add support for reloading application running in a container instead of rolling update about reloader HOT 5 OPEN

Here's how vmware does it in their fluentd operator: https://github.com/vmware/kube-fluentd-operator/blob/master/config-reloader/fluentd/reloader.go#L26

Basically we have to enable rpc endpoint for fluentfd as mentioned here: https://docs.fluentd.org/v1.0/articles/rpc#configuration

In general, we can add support for reloading applications via RPC endpoint

• An application will contain annotation with the RPC endpoint to call
• Instead of rolling update, we can call the RPC endpoint mentioned (in all pods)

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I would also like to put in consideration for applications with required bootstrapping on start or restart. Unless this will be implemented towards very specifically defined apps or those running behind process managers. I'm not sure how this would work out, seems very diverse?

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Yes it will be awesome to have this feature in place! e.g. in case of fluentd assume we have 50 nodes then it will take too much for rolling update of all pods in the daemonset; but if have restart of process then it will happen at sametime in all

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Question : how it will guarantee HA of application? Will it respect deployment settings during restarting?

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We're using https://github.com/weaveworks/watch for this purpose:

1. Mount the configmap as volume into a side-car running watch
2. Watch the mount point/files in it
3. Trigger the reload by issueing a curl command to the actual app

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