Enhance helper Pod interface and configuration.

.dockerignore

@@ -1,3 +1,4 @@
 ./.dapper
 ./.cache
 ./dist
+./examples/cache/testmount

.gitignore

@@ -5,4 +5,7 @@
 *.swp
 .idea
 .vscode/
-Dockerfile.dapper[0-9]*
+Dockerfile.dapper[0-9]*
+local-path-provisioner
+/examples/cache/testmount
+

README.md

@@ -119,7 +119,7 @@ Now you've verified that the provisioner works as expected.
 
 ### Customize the ConfigMap
 
-The configuration of the provisioner is a json file `config.json` and two bash scripts `setup` and `teardown`, stored in the a config map, e.g.:
+The configuration of the provisioner is a json file `config.json`, a Pod template `helper-pod.yaml` and two bash scripts `setup` and `teardown`, e.g.:
 ```
 kind: ConfigMap
 apiVersion: v1
@@ -146,41 +146,13 @@ data:
         }
   setup: |-
         #!/bin/sh
-        while getopts "m:s:p:" opt
-        do
-            case $opt in
-                p)
-                absolutePath=$OPTARG
-                ;;
-                s)
-                sizeInBytes=$OPTARG
-                ;;
-                m)
-                volMode=$OPTARG
-                ;;
-            esac
-        done
-
-        mkdir -m 0777 -p ${absolutePath}
+        set -eu
+        mkdir -m 0777 -p "$VOL_DIR"
   teardown: |-
         #!/bin/sh
-        while getopts "m:s:p:" opt
-        do
-            case $opt in
-                p)
-                absolutePath=$OPTARG
-                ;;
-                s)
-                sizeInBytes=$OPTARG
-                ;;
-                m)
-                volMode=$OPTARG
-                ;;
-            esac
-        done
-
-        rm -rf ${absolutePath}
-  helperPod.yaml: |-
+        set -eu
+        rm -rf "$VOL_DIR"
+  helper-pod.yaml: |-
         apiVersion: v1
         kind: Pod
         metadata:
@@ -209,16 +181,26 @@ The configuration must obey following rules:
 3. No duplicate paths allowed for one node.
 4. No duplicate node allowed.
 
-#### Scripts `setup` and `teardown` and `helperPod.yaml`
+#### Scripts `setup` and `teardown` and the `helper-pod.yaml` template
 
-The script `setup` will be executed before the volume is created, to prepare the directory on the node for the volume.
+* The `setup` script is run before the volume is created, to prepare the volume directory on the node.
+* The `teardown` script is run after the volume is deleted, to cleanup the volume directory on the node.
+* The `helper-pod.yaml` template is used to create a helper Pod that runs the `setup` or `teardown` script.
 
-The script `teardown` will be executed after the volume is deleted, to cleanup the directory on the node for the volume.
+The scripts receive their input as environment variables:
 
-The yaml file `helperPod.yaml` will be created by local-path-storage to execute `setup` or `teardown` script with three paramemters  `-p <path> -s <size> -m <mode>` :
-* path: the absolute path provisioned on the node
-- size: pvc.Spec.resources.requests.storage in bytes
-* mode: pvc.Spec.VolumeMode
+| Environment variable | Description |
+| -------------------- | ----------- |
+| `VOL_DIR` | Volume directory that should be created or removed. |
+| `VOL_NAME` | Name of the PersistentVolume. |
+| `VOL_Mode` | The PersistentVolume mode (`Block` or `Filesystem`). |
+| `VOL_SIZE_BYTES` | Requested volume size in bytes. |
+| `PVC_NAME` | Name of the PersistentVolumeClaim. |
+| `PVC_NAMESPACE` | Namespace of the PersistentVolumeClaim. |
+| `PVC_ANNOTATION` | Value of the PersistentVolumeClaim annotation specified by the manager's `--pvc-annotation` option. |
+| `PVC_ANNOTATION_{SUFFIX}` | Value of the PersistentVolumeClaim annotation with the prefix specified by the manager's `--pvc-annotation` option. The `SUFFIX` is the normalized path within the annotation name after the `/`. E.g. if `local-path-provisioner` is run with `--pvc-annotation=storage.example.org` the PVC annotation `storage.example.org/cache-name` is passed through to the Pod as env var `PVC_ANNOTATION_CACHE_NAME`. If the helper Pod requires such an annotation `local-path-provisioner` can be run with e.g. `--pvc-annotation-required=storage.example.org/cache-name`. |
+
+Additional environment variables and defaults for the optional `PVC_ANNOTATION*` can be specified within the helper Pod template.
 
 #### Reloading
 

debug/config.yaml

@@ -39,41 +39,11 @@ data:
         }
   setup: |-
         #!/bin/sh
-        while getopts "m:s:p:" opt
-        do
-            case $opt in
-                p)
-                absolutePath=$OPTARG
-                ;;
-                s)
-                sizeInBytes=$OPTARG
-                ;;
-                m)
-                volMode=$OPTARG
-                ;;
-            esac
-        done
-
-        mkdir -m 0777 -p ${absolutePath}
+        mkdir -m 0777 -p "$VOL_DIR"
   teardown: |-
         #!/bin/sh
-        while getopts "m:s:p:" opt
-        do
-            case $opt in
-                p)
-                absolutePath=$OPTARG
-                ;;
-                s)
-                sizeInBytes=$OPTARG
-                ;;
-                m)
-                volMode=$OPTARG
-                ;;
-            esac
-        done
-
-        rm -rf ${absolutePath}
-  helperPod.yaml: |-
+        rm -rf "$VOL_DIR"
+  helper-pod.yaml: |-
         apiVersion: v1
         kind: Pod
         metadata:

deploy/chart/templates/configmap.yaml

@@ -13,6 +13,6 @@ data:
     {{ .Values.configmap.setup | nindent 4 }}
   teardown: |-
     {{ .Values.configmap.teardown | nindent 4 }}
-  helperPod.yaml: |-
+  helper-pod.yaml: |-
     {{ .Values.configmap.helperPod | nindent 4 }}
 

deploy/chart/values.yaml

@@ -93,41 +93,12 @@ configmap:
   # specify the custom script for setup and teardown
   setup: |-
     #!/bin/sh
-    while getopts "m:s:p:" opt
-    do
-        case $opt in
-            p)
-            absolutePath=$OPTARG
-            ;;
-            s)
-            sizeInBytes=$OPTARG
-            ;;
-            m)
-            volMode=$OPTARG
-            ;;
-        esac
-    done
-
-    mkdir -m 0777 -p ${absolutePath}
+    set -eu
+    mkdir -m 0777 -p "$VOL_DIR"
   teardown: |-
     #!/bin/sh
-    while getopts "m:s:p:" opt
-    do
-        case $opt in
-            p)
-            absolutePath=$OPTARG
-            ;;
-            s)
-            sizeInBytes=$OPTARG
-            ;;
-            m)
-            volMode=$OPTARG
-            ;;
-        esac
-    done
-
-    rm -rf ${absolutePath}
-  # specify the custom helper pod yaml
+    set -eu
+    rm -rf "$VOL_DIR"
   helperPod: |-
     apiVersion: v1
     kind: Pod

deploy/example-config.yaml

@@ -23,41 +23,13 @@ data:
     }
   setup: |-
     #!/bin/sh
-    while getopts "m:s:p:" opt
-    do
-        case $opt in
-            p)
-            absolutePath=$OPTARG
-            ;;
-            s)
-            sizeInBytes=$OPTARG
-            ;;
-            m)
-            volMode=$OPTARG
-            ;;
-        esac
-    done
-
-    mkdir -m 0777 -p ${absolutePath}
+    set -eu
+    mkdir -m 0777 -p "$VOL_DIR"
   teardown: |-
     #!/bin/sh
-    while getopts "m:s:p:" opt
-    do
-        case $opt in
-            p)
-            absolutePath=$OPTARG
-            ;;
-            s)
-            sizeInBytes=$OPTARG
-            ;;
-            m)
-            volMode=$OPTARG
-            ;;
-        esac
-    done
-
-    rm -rf ${absolutePath}
-  helperPod.yaml: |-
+    set -eu
+    rm -rf "$VOL_DIR"
+  helper-pod.yaml: |-
     apiVersion: v1
     kind: Pod
     metadata:
@@ -66,5 +38,3 @@ data:
       containers:
       - name: helper-pod
         image: busybox
-
-

deploy/local-path-storage.yaml

@@ -110,41 +110,13 @@ data:
     }
   setup: |-
     #!/bin/sh
-    while getopts "m:s:p:" opt
-    do
-        case $opt in
-            p)
-            absolutePath=$OPTARG
-            ;;
-            s)
-            sizeInBytes=$OPTARG
-            ;;
-            m)
-            volMode=$OPTARG
-            ;;
-        esac
-    done
-
-    mkdir -m 0777 -p ${absolutePath}
+    set -eu
+    mkdir -m 0777 -p "$VOL_DIR"
   teardown: |-
     #!/bin/sh
-    while getopts "m:s:p:" opt
-    do
-        case $opt in
-            p)
-            absolutePath=$OPTARG
-            ;;
-            s)
-            sizeInBytes=$OPTARG
-            ;;
-            m)
-            volMode=$OPTARG
-            ;;
-        esac
-    done
-
-    rm -rf ${absolutePath}
-  helperPod.yaml: |-
+    set -eu
+    rm -rf "$VOL_DIR"
+  helper-pod.yaml: |-
     apiVersion: v1
     kind: Pod
     metadata:
@@ -153,5 +125,3 @@ data:
       containers:
       - name: helper-pod
         image: busybox
-
-

examples/cache/README.md

@@ -0,0 +1,56 @@
+# Example cache provisioner
+
+This example shows how to use short-lived PersistentVolumes for caching.
+A [buildah](https://github.com/containers/buildah)-based helper Pod is used to provision a container file system based on an image as PersistentVolume and commit it when deprovisioning.
+Users can select the desired cache or rather the image using a PersistentVolumeClaim annotation that is passed through to the helper Pod as environment variable.  
+
+While it is not part of this example caches could also be synchronized across nodes using an image registry.
+The [cache-provisioner](https://github.com/mgoltzsche/cache-provisioner) project aims to achieve this as well as other cache management features.
+
+## Test
+
+### Test the helper Pod separately
+
+The helper Pod can be tested separately using docker locally:
+```sh
+./helper-test.sh
+```
+
+### Test the integration
+
+_Please note that a non-overlayfs storage directory (`/data/example-cache-storage`) must be configured._
+_The provided configuration is known to work with minikube (`minikube start`) and kind (`kind create cluster; kind export kubeconfig`)._  
+
+Install the example kustomization:
+```sh
+kustomize build . | kubectl apply -f -
+```
+
+If you want to test changes to the `local-path-provisioner` binary locally:
+```sh
+kubectl delete -n example-cache-storage deploy example-cache-local-path-provisioner
+(
+	cd ../..
+	go build .
+	./local-path-provisioner --debug start \
+		--namespace=example-cache-storage \
+		--configmap-name=example-cache-local-path-config \
+		--service-account-name=example-cache-local-path-provisioner-service-account \
+		--provisioner-name=storage.example.org/cache \
+		--pvc-annotation=storage.example.org \
+		--pvc-annotation-required=storage.example.org/cache-name
+)
+```
+
+Within another terminal create an example Pod and PVC that pulls and runs a container image using [podman](https://github.com/containers/podman):
+```sh
+kubectl apply -f test-pod.yaml
+kubectl logs -f cached-build
+```
+
+If the Pod and PVC are removed and recreated you can observe that, during the 2nd Pod execution on the same node, the image for the nested container doesn't need to be pulled again since it is cached:
+```sh
+kubectl delete -f test-pod.yaml
+kubectl apply -f test-pod.yaml
+kubectl logs -f cached-build
+```

examples/cache/config/config.json

@@ -0,0 +1,16 @@
+{
+  "nodePathMap": [
+    {
+      "node": "DEFAULT_PATH_FOR_NON_LISTED_NODES",
+      "paths": ["/data/example-cache-storage"]
+    },
+    {
+    	  "node": "minikube",
+      "paths": ["/data/example-cache-storage"]
+    },
+    {
+    	  "node": "kind-control-plane",
+      "paths": ["/var/opt/example-cache-storage"]
+    }
+  ]
+}

examples/cache/config/helper-pod.yaml

@@ -0,0 +1,15 @@
+apiVersion: v1
+kind: Pod
+metadata:
+  name: helper-pod
+spec:
+  containers:
+  - name: helper
+    image: quay.io/buildah/stable:v1.18.0
+    imagePullPolicy: IfNotPresent
+    securityContext:
+      privileged: true
+      hostPID: true
+    volumeMounts:
+    - name: data
+      mountPropagation: Bidirectional