I’m yet to deploy anything to a production k8s cluster, so I’m looking for opinions of people that know what they’re talking about.
It also lies about the actual status of the installation. A deployment that applies successfully but has issues with the new pods coming up can still show successful.
The larger charts are a nightmare which isn’t helm’s fault but it doesn’t make things appreciably easier either.
Kustomize has a lot of warts too. If the type definition in k8s source doesn’t have a merge key defined, it’s going to overwrite the entire section of the resource. You can use JsonPatches to get around that problem but that is super gross too.
The entire ecosystem is trying to solve the same problem and no one has come up with the definitive way of doing it (because it’s a HARD problem) It seems like Helm templating and then passing to kustomize to add in the one-off changes is the direction a lot of people are heading but it’s more of a least-bad solution than a good one.
I will say, if you’re using helm templates for your own stuff, you very likely going to be happy with it.
You can define a component which you install into many clusters and then slightly differentiate them based on cluster parameters, kind of like Puppet or Chef (without the application stage)
Alongside this, you can actually patch helm charts. An example component can be found here https://github.com/jaxxstorm/kr8-cfgmgmt-example/blob/master...
The patches.jsonnet allows you to add a commandline flag that wasn't in the helm chart at one time.
Seriously though, gonna look closer at this tomorrow at the office. Thanks for the heads up!
(Title = Customizing Upstream Helm Charts with Kustomize)
I use helm fetch and pull the charts with dependencies into my repo. Running direct from the public repo is a little bit too much like piping the contents of a url to bash without checking first.
You can then customize however you like.
When I want to update the charts, helm fetch it again and merge the changes.
If you want to: have PITA with RBAC, forget about manual changes because there are no 3-way-merge in Helm2 (that's what kubectl apply does, only hope it will be in Helm 3) and after this change helm cannot apply desired state, some of the biggest pains lasting for years had been resolved only in 2.13 with --atomic parameter.
Aside from dependency resolution, everything that Helm does could be made by any template engine + API caller.
Unfortunately, many of those stable charts for core infrastructure are barely POC-worthy and take a great deal of effort to get into production state. For example, there is no helm chart for Kafka with TLS support. Maybe not necessary for every production implementation, but dammit, this is 2019.
That said, helm is not safe. A helm "release" is not an artifact. It's a deployment of a helm chart of a certain version. That helm chart version may or may not correlate to the underlying version of the software you're running as that artifact is presumably defined with an "image" in values.
For example, I've run the same aforementioned MSSQL helm chart with 2017-CU7-ubuntu, 2017-CU8-ubuntu, and 2017-CU9-ubuntu tags. A quick "helm list" might show you the same chart version across three different environments but they're still very different.
Helm is not idempotent. Helm upgrade is a nightmare. One has to perform a helm upgrade to set values. Helm upgrades often fail. Even though they report failure, a look under the hood reveals that it actually succeeded.
Occasionally a helm upgrade blows away the persistent volume attached to a stateful thing. That's always the best.
tl;dr helm is the most popular, but has some massive shortcomings so we're all looking for something to replace it and kustomize is exciting because it's now for better or worse part of the core.