helmfile sync vs helmfile apply
Jan 12
sync sync all resources from state file (repos, releases and chart deps) apply apply all resources from state file only when there are changes
sync
The helmfile sync sub-command sync your cluster state as described in your helmfile ... Under the covers, Helmfile executes helm upgrade --install for each release declared in the manifest, by optionally decrypting secrets to be consumed as helm chart values. It also updates specified chart repositories and updates the dependencies of any referenced local charts. For Helm 2.9+ you can use a username and password to authenticate to a remote repository.
apply
The helmfile apply sub-command begins by executing diff. If diff finds that there is any changes sync is executed. Adding --interactive instructs Helmfile to request your confirmation before sync. An expected use-case of apply is to schedule it to run periodically, so that you can auto-fix skews between the desired and the current state of your apps running on Kubernetes clusters.
I went through the Helmfile repo Readme to figure out the difference between helmfile sync and helmfile apply. It seems that unlike the apply command, the sync command doesn't do a diff and helm upgrades the hell out of all releases 😃. But from the word sync, you'd expect the command to apply those releases that have been changed. There is also mention of the potential application of helmfile apply to periodically syncing of releases. Why not use helmfile sync for this purpose? Overall, the difference didn't become crystal clear, and I though there could probably be more to it. So, I'm asking.
kubernetes1 answer
Accepted answer · original discussion
Feb 13
Consider the use case where you have a Jenkins job that gets triggered every 5 minutes and in that job you want to upgrade your helm chart, but only if there are changes.
If you use helmfile sync which calls helm upgrade --install every five minutes, you will end up incrementing Chart revision every five minutes.
$ helm upgrade --install httpd bitnami/apache > /dev/null
$ helm list
NAME REVISION UPDATED STATUS CHART APP VERSION NAMESPACE
httpd 1 Thu Feb 13 11:27:14 2020 DEPLOYED apache-7.3.5 2.4.41 default
$ helm upgrade --install httpd bitnami/apache > /dev/null
$ helm list
NAME REVISION UPDATED STATUS CHART APP VERSION NAMESPACE
httpd 2 Thu Feb 13 11:28:39 2020 DEPLOYED apache-7.3.5 2.4.41 default
So, each helmfile sync will result new revision. Now if you were to run helmfile apply, which will first check for diffs and only then (if found) will call helmfile sync which will in turn call helm upgrade --install this will not happen.
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