75 lines
2.2 KiB
Markdown
75 lines
2.2 KiB
Markdown
Kontemplate tips & tricks
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=========================
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<!-- markdown-toc start - Don't edit this section. Run M-x markdown-toc-refresh-toc -->
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**Table of Contents**
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- [Kontemplate tips & tricks](#kontemplate-tips--tricks)
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- [Update Deployments when ConfigMaps change](#update-deployments-when-configmaps-change)
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- [direnv & pass](#direnv--pass)
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<!-- markdown-toc end -->
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## Update Deployments when ConfigMaps change
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Kubernetes does [not currently][] have the ability to perform rolling updates
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of Deployments and other resource types when `ConfigMap` or `Secret` objects
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are updated.
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It is possible to make use of annotations and templating functions in
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Kontemplate to force updates to these resources anyways (assuming that the
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`ConfigMap` or `Secret` contains interpolated variables).
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For example:
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```yaml
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# A ConfigMap that contains some data structure in JSON format
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---
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kind: ConfigMap
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metadata:
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name: app-config
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data:
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configFile: {{ .appConfig | json }}
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```
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Now whenever the `appConfig` variable changes we would like to update the
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`Deployment` making use of it, too. We can do this by adding a hash of the
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configuration to the annotations of the created `Pod` objects:
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```yaml
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---
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kind: Deployment
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metadata:
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name: app
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spec:
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template:
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metadata:
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annotations:
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configHash: {{ .appConfig | json | sha256sum }}
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spec:
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containers:
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- name: app
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# Some details omitted ...
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volumeMounts:
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- name: config
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mountPath: /etc/app/
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volumes:
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- name: config
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configMap:
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name: app-config
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```
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Now if the `ConfigMap` object appears first in the resource files, `kubectl`
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will apply the resources sequentially and the updated annotation will cause
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a rolling update of all relevant pods.
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## direnv & pass
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Users of `pass` may have multiple different password stores on their machines.
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Assuming that `kontemplate` configuration exists somewhere on the filesystem
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per project, it is easy to use [direnv][] to switch to the correct
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`PASSWORD_STORE_DIR` variable when entering the folder.
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[not currently]: https://github.com/kubernetes/kubernetes/issues/22368
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[direnv]: https://direnv.net/
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