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Kontemplate tips & tricks
=========================
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**Table of Contents**
- [Kontemplate tips & tricks](#kontemplate-tips--tricks)
- [Update Deployments when ConfigMaps change](#update-deployments-when-configmaps-change)
- [direnv & pass](#direnv--pass)
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## Update Deployments when ConfigMaps change
Kubernetes does [not currently][] have the ability to perform rolling updates
of Deployments and other resource types when `ConfigMap` or `Secret` objects
are updated.
It is possible to make use of annotations and templating functions in
Kontemplate to force updates to these resources anyways.
For example:
```yaml
# A ConfigMap that contains some configuration for your app
---
kind: ConfigMap
metadata:
name: app-config
data:
app.conf: |
name: {{ .appName }}
foo: bar
```
Now whenever the `appName` variable changes or we make an edit to the
`ConfigMap` we would like to update the `Deployment` making use of it, too. We
can do this by adding a hash of the parsed template to the annotations of the
created `Pod` objects:
```yaml
---
kind: Deployment
metadata:
name: app
spec:
template:
metadata:
annotations:
configHash: {{ insertTemplate "app-config.yaml" | sha256sum }}
spec:
containers:
- name: app
# Some details omitted ...
volumeMounts:
- name: config
mountPath: /etc/app/
volumes:
- name: config
configMap:
name: app-config
```
Now any change to the `ConfigMap` - either by directly editing the yaml file or
via a changed template variable - will cause the annotation to change,
triggering a rolling update of all relevant pods.
## direnv & pass
Users of `pass` may have multiple different password stores on their machines.
Assuming that `kontemplate` configuration exists somewhere on the filesystem
per project, it is easy to use [direnv][] to switch to the correct
`PASSWORD_STORE_DIR` variable when entering the folder.
[not currently]: https://github.com/kubernetes/kubernetes/issues/22368
[direnv]: https://direnv.net/
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