Chart last mile example

bin/pre-commit.sh

@@ -32,9 +32,11 @@ function testGoTest {
   go test -v ./...
 }
 
+# This is helm stuff.
 function testNoTravisGoTest {
   go test -v sigs.k8s.io/kustomize/pkg/target \
       -run TestChartInflatorExecPlugin -tags=notravis
+  mdrip --mode test --label helmtest README.md ./examples/chart.md
 }
 
 function testExamples {

examples/README.md

@@ -14,6 +14,9 @@ go get sigs.k8s.io/kustomize
    (differently configured) variants of a simple Hello
    World server.
 
+ * [last mile helm](chart.md) - Make last mile modifications to
+   a helm chart.
+   
  * [LDAP](ldap/README.md) - Deploy multiple
    (differently configured) variants of a LDAP server.
 

examples/chart.md

@@ -0,0 +1,255 @@
+# kustomization of a helm chart
+
+[last mile]: https://testingclouds.wordpress.com/2018/07/20/844/
+[stable chart]: https://github.com/helm/charts/tree/master/stable
+[Helm charts]: https://github.com/helm/charts
+[_minecraft_]: https://github.com/helm/charts/tree/master/stable/minecraft
+[plugin]: ../plugins.md
+
+[Helm charts] aren't natively read by kustomize, but
+kustomize has a [plugin] system that allows one to
+access helm charts.
+
+One pattern combining kustomize and helm is
+the [last mile] modification, where
+one uses an inflated chart as a base, then
+modifies it on the way to the cluster using
+kustomize.
+
+The plugin used in the example below is coded to work
+only for charts found in the [stable chart] repo.  The
+example arbitrarily uses [_minecraft_], but should work
+for any chart.
+
+The following example assumes you have `helm`
+on your `$PATH`.
+
+Make a place to work:
+
+<!-- @makeWorkplace @helmtest -->
+```
+DEMO_HOME=$(mktemp -d)
+mkdir -p $DEMO_HOME/base
+mkdir -p $DEMO_HOME/dev
+mkdir -p $DEMO_HOME/prod
+```
+
+## Use a remote chart
+
+Define a kustomization representing your _development_
+variant (aka environment).
+
+This could involve any number of kustomizations (see
+other examples), but in this case just add the name
+prefix `dev-` to all resources:
+
+<!-- @writeKustDev @helmtest -->
+```
+cat <<'EOF' >$DEMO_HOME/dev/kustomization.yaml
+namePrefix:  dev-
+resources:
+- ../base
+EOF
+```
+
+Likewise define a _production_ variant, with a name
+prefix `prod-`:
+
+<!-- @writeKustProd @helmtest -->
+```
+cat <<'EOF' >$DEMO_HOME/prod/kustomization.yaml
+namePrefix:  prod-
+resources:
+- ../base
+EOF
+```
+
+These two variants refer to a common base.
+
+Define this base:
+
+<!-- @writeKustDev @helmtest -->
+```
+cat <<'EOF' >$DEMO_HOME/base/kustomization.yaml
+generators:
+- chartInflator.yaml
+EOF
+```
+
+The base refers to a generator configuration file
+called `chartInflator.yaml`.
+
+This file lets one specify the name of a [stable chart],
+and other things like a path to a values file, defaulting
+to the `values.yaml` that comes with the chart.
+
+Create the config file `chartInflator.yaml`, specifying
+the arbitrarily chosen chart name _minecraft_:
+
+<!-- @writeGeneratorConfig @helmtest -->
+```
+cat <<'EOF' >$DEMO_HOME/base/chartInflator.yaml
+apiVersion: someteam.example.com/v1
+kind: ChartInflatorExec
+metadata:
+  name: notImportantHere
+chartName: minecraft
+EOF
+```
+
+Because this particular YAML file is listed in the
+`generators:` stanza of a kustomization file, it is
+treated as the binding between a generator plugin -
+identified by the _apiVersion_ and _kind_ fields - and
+other fields that configure the plugin.
+
+Download the plugin to your `DEMO_HOME` and make it
+executable:
+
+<!-- @installPlugin @helmtest -->
+```
+plugin=plugin/someteam.example.com/v1/ChartInflatorExec
+curl -s --create-dirs -o \
+"$DEMO_HOME/kustomize/$plugin" \
+"https://raw.githubusercontent.com/\
+kubernetes-sigs/kustomize/master/$plugin"
+
+chmod a+x $DEMO_HOME/kustomize/$plugin
+```
+
+Check the directory layout:
+
+<!-- @tree -->
+```
+tree $DEMO_HOME
+```
+
+Expect something like:
+
+> ```
+> /tmp/whatever
+> ├── base
+> │   ├── chartInflator.yaml
+> │   └── kustomization.yaml
+> ├── dev
+> │   └── kustomization.yaml
+> ├── kustomize
+> │   └── plugin
+> │       └── someteam.example.com
+> │           └── v1
+> │               └── ChartInflatorExec
+> └── prod
+>    └── kustomization.yaml
+> ```
+
+Define a helper function to run kustomize with the
+correct environment and flags for plugins:
+
+<!-- @defineKustomizeIt @helmtest -->
+```
+function kustomizeIt {
+  XDG_CONFIG_HOME=$DEMO_HOME \
+  kustomize build \
+    --enable_alpha_goplugins_accept_panic_risk \
+    $DEMO_HOME/$1
+}
+```
+
+Finally, build the `prod` variant.  Notice that all
+resource  names now have the `prod-` prefix:
+
+<!-- @doProd @helmtest -->
+```
+clear
+kustomizeIt prod
+```
+
+Compare `dev` to `prod`:
+
+<!-- @doCompare -->
+```
+diff <(kustomizeIt dev) <(kustomizeIt prod) | more
+```
+
+To see the unmodified but inflated chart, run kustomize
+on the base.  Every invocation here is re-downloading
+and re-inflating the chart.
+
+<!-- @showBase @helmtest -->
+```
+kustomizeIt base
+```
+
+
+## Use a local chart
+
+The example above fetches a new copy of the chart
+to a temporary directory with each kustomize
+build, because a local chart home isn't specified
+in the configuration.
+
+To suppress fetching, specify a _chart home_
+explicitly, and just make sure the chart is already
+there.
+
+To demo this so that it won't interfere with your
+existing helm environment, do this:
+
+<!-- @helmInit @helmtest -->
+```
+helmHome=$DEMO_HOME/dothelm
+chartHome=$DEMO_HOME/base/charts
+
+function doHelm {
+  helm --home $helmHome $@
+}
+
+# Create helm config files in a new location.
+# The init command is extremely chatty
+doHelm init --client-only >& /dev/null
+```
+
+Now download a chart; again use _minecraft_
+(but you could use anything):
+
+<!-- @fetchChart @helmtest -->
+```
+doHelm fetch --untar \
+    --untardir $chartHome \
+    stable/minecraft
+```
+
+The tree has more stuff now; helm config data
+and a complete copy of the chart:
+<!-- @tree -->
+```
+tree $DEMO_HOME
+```
+
+
+Add a `chartHome` field to the generator config file so
+that it knows where to find the local chart:
+
+<!-- @modifyGenConfig @helmtest -->
+```
+echo "chartHome: $chartHome" >>$DEMO_HOME/base/chartInflator.yaml
+```
+
+Change the values file, to show that the results
+generated below are from the _locally_ stored chart:
+
+<!-- @valueChange @helmtest -->
+```
+sed -i 's/CHANGEME!/SOMETHINGELSE/' $chartHome/minecraft/values.yaml
+sed -i 's/LoadBalancer/NodePort/' $chartHome/minecraft/values.yaml
+```
+
+Finally, built it
+
+<!-- @finalProd @helmtest -->
+```
+kustomizeIt prod
+```
+
+and observe the change from `LoadBalancer` to `NodePort`, and 
+the change in the encoded password.