Add image_aliases and hook script support (#9)

.drone.example.yml

@@ -1,5 +1,8 @@
 pipeline:
   build:
     image: quay.io/testcontainers/dind-drone-plugin
-    build_image: openjdk:8-jdk
-    cmd: java -v
+    build_image: alpine:fake
+    cmd: cat /etc/issue
+    image_aliases:
+      alpine:3.5: alpine:fake
+      alpine:3.6: alpine:fake2

Dockerfile

@@ -1,9 +1,12 @@
 FROM docker:19.03.0-dind
 
-RUN apk add --no-cache bash
+RUN apk add --no-cache bash jq
 
 #### Script that starts docker in docker
-ADD command.sh /command.sh
-RUN chmod +x /command.sh
+ADD command.sh /dind-drone-plugin/command.sh
+RUN chmod +x /dind-drone-plugin/command.sh
 
-ENTRYPOINT ["/command.sh"]
+#### Hook scripts
+ADD hooks /dind-drone-plugin/hooks
+
+ENTRYPOINT ["/dind-drone-plugin/command.sh"]

README.md

@@ -28,11 +28,21 @@ pipeline:
   build:
     image: quay.io/testcontainers/dind-drone-plugin
     build_image: openjdk:8-jdk-alpine
-    # This specifies the command that should be executed to perform build, test and integration tests. Not to be confused with Drone's `command`:
+    # This specifies the command that should be executed to perform build, test and 
+    #  integration tests. Not to be confused with Drone's `command`:
     cmd: ./gradlew clean check --info
-    # Not mandatory, but enables pre-fetching of images in parallel with the build, so may save time:
+    # Not mandatory; enables pre-fetching of images in parallel with the build, so may save 
+    #  time:
     prefetch_images:
       - "redis:4.0.6"
+    # Not mandatory; sets up image name 'aliases' by pulling from one registry and tagging
+    #  as a different name. Intended as a simplistic mechanism for using a private registry 
+    #  rather than Docker Hub for a known set of images. Accepts a dictionary of
+    #  private registry image name to the Docker Hub image that it is a substitute for.
+    #  Note that all images are pulled synchronously before the build starts, so this is
+    #  inefficient if any unnecessary images are listed.
+    image_aliases:
+      someregistry.com/redis:4.0.6: redis:4.0.6
 ```
 
 When migrating to use this plugin from an ordinary build step, note that:
@@ -41,8 +51,16 @@ When migrating to use this plugin from an ordinary build step, note that:
 * `image` should be changed to `build_image`
 * `prefetch_images` is optional, but recommended. This specifies a list of images that should be pulled in parallel with your build process, thus saving some time.
 
+## Extending
+
+Users with custom requirements can build a new image using this as a base image.
+
+This image uses hook scripts, if present, to perform custom actions. Such scripts may be placed as executable files in any of `/dind-drone-plugin/hooks/{pre_daemon_start,post_daemon_start,pre_run,post_run}`, depending on which phase they are required to run in.
+
+Some initial hook scripts already exist, which should be overwritten or removed if needed.
+
 ## Copyright
 
 This repository contains code which was mainly developed at [Skyscanner](https://www.skyscanner.net/jobs/), and is licenced under the [Apache 2.0 Licence](LICENSE).
 
-(c) 2017-2019 Skyscanner Ltd.
+(c) 2017-2020 Skyscanner Ltd.

command.sh

@@ -2,6 +2,15 @@
 
 set -euo pipefail # Abort on error, strict variable interpolation, fail if piped command fails
 
+run_hook_scripts() {
+  for HOOK_SCRIPT in /dind-drone-plugin/hooks/$1/*; do
+    if [[ -x $HOOK_SCRIPT ]]; then
+      echo "📄 Running $1 hook script $HOOK_SCRIPT"
+      /bin/bash $HOOK_SCRIPT || exit 1
+    fi
+  done
+}
+
 if [[ "${PLUGIN_CMD:-}" == "" ]]; then
   echo "One or more cmd arguments must be provided"
   exit 1
@@ -13,6 +22,8 @@ export PLUGIN_CMD=${PLUGIN_CMD//,/ && }
 # Wrap command scriptlet in an invocation of sh
 export PLUGIN_CMD="sh -c '${PLUGIN_CMD}'"
 
+run_hook_scripts pre_daemon_start
+
 echo "📦 Starting dind-drone-plugin"
 
 echo "🐳 Starting docker-in-docker daemon"
@@ -32,24 +43,13 @@ done
 docker ps &> /dev/null || exit 1
 echo "✅ Docker-in-Docker is running..."
 
-if [[ "${PLUGIN_DOCKER_LOGIN_COMMAND:-}" != "" ]]; then
-  echo "🛠  Executing Docker login command"
-  sh -c "${PLUGIN_DOCKER_LOGIN_COMMAND}" 2>&1 | sed "s/^/    /g"
-fi
+run_hook_scripts post_daemon_start
 
-if [[ "${PLUGIN_PREFETCH_IMAGES:-}" != "" ]]; then
-  echo "🚚 Prefetching images in background:"
-  for IMG in $(echo ${PLUGIN_PREFETCH_IMAGES} | sed "s/,/ /g"); do
-    echo "   $IMG"
-    $(docker pull "$IMG" > /dev/null) &
-  done
-fi
+echo "   Available images before build:"
+docker image ls 2>&1 | sed 's/^/   /g'
 
 cd ${CI_WORKSPACE}
 
-echo "🚚 Pulling build image: ${PLUGIN_BUILD_IMAGE}"
-docker pull ${PLUGIN_BUILD_IMAGE} 2>&1 | sed 's/^/   /g'
-
 # Ensure that secrets (passed through as env vars) are available. Iterate and purposefully omit newlines.
 for k in $(compgen -e); do
   echo $k=${!k} >> ${PWD}/outer_env_vars.env
@@ -65,6 +65,9 @@ echo "ℹ️  DOCKER_HOST will be set to tcp://${DOCKER_IP}:2375"
 echo "ℹ️  Containers spawned by the build container will be accessible at ${DOCKER_IP} (do not hardcode this value)"
 
 echo -e "\n\n"
+
+run_hook_scripts pre_run
+
 MSG="🚀 About to run command: ${PLUGIN_CMD} on image ${PLUGIN_BUILD_IMAGE} inside Docker-in-Docker"
 echo -e $MSG
 echo -n " $MSG" | sed 's/./=/g'
@@ -85,6 +88,8 @@ CMD_EXIT_CODE=$?
 echo; echo
 echo "🏁 Exit code: $CMD_EXIT_CODE"
 
+run_hook_scripts post_run
+
 rm outer_env_vars.env
 
 exit $CMD_EXIT_CODE

hooks/post_daemon_start/10-docker-login-command.sh

@@ -0,0 +1,6 @@
+#!/bin/bash
+
+if [[ "${PLUGIN_DOCKER_LOGIN_COMMAND:-}" != "" ]]; then
+  echo "🛠  Executing Docker login command"
+  sh -c "${PLUGIN_DOCKER_LOGIN_COMMAND}" 2>&1 | sed "s/^/    /g"
+fi

hooks/post_daemon_start/20-image-aliases.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+
+echo $PLUGIN_IMAGE_ALIASES | jq -r 'to_entries[] | [.key, .value] | @tsv' | while read ORIGINAL NEW; do
+    echo "🐑 Pulling image $ORIGINAL and retagging as $NEW"
+    docker pull $ORIGINAL 2>&1 | sed 's/^/   /g'
+    docker tag $ORIGINAL $NEW 2>&1 | sed 's/^/   /g'
+done

hooks/post_daemon_start/30-image-prefetch.sh

@@ -0,0 +1,18 @@
+#!/bin/bash
+
+pull_if_absent() {
+  if [[ $(docker images ${1} | wc -l) < 2 ]]; then
+    echo "🚚 Pulling image: ${1}"
+    docker pull ${1} 2>&1 | sed 's/^/   /g'
+  fi
+}
+
+if [[ "${PLUGIN_PREFETCH_IMAGES:-}" != "" ]]; then
+  echo "🚚 Prefetching images in background:"
+  for IMG in $(echo ${PLUGIN_PREFETCH_IMAGES} | sed "s/,/ /g"); do
+    echo "   $IMG"
+    pull_if_absent "$IMG" > /dev/null &
+  done
+fi
+
+pull_if_absent ${PLUGIN_BUILD_IMAGE}