re-use CSS compilation cached assets in pre-merge builds

refs DE-1379

[build-registry-path=jenkins/canvas-lms/de-1379-3]
[change-merged]

Change-Id: I1e33e24ee61afa114739cbd4acd9eddb163e1f76
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/301709
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
QA-Review: Aaron Ogata <aogata@instructure.com>
Product-Review: Aaron Ogata <aogata@instructure.com>
Reviewed-by: Andrea Cirulli <andrea.cirulli@instructure.com>
Build-Review: Andrea Cirulli <andrea.cirulli@instructure.com>

Dockerfile.jenkins.webpack-runner

@@ -1,8 +1,11 @@
 FROM local/webpack-builder
 
-RUN --mount=type=bind,from=local/cache-helper,source=/tmp/dst,target=/cache-helper \
+RUN \
+  --mount=type=bind,from=local/cache-helper,source=/tmp/dst,target=/cache-helper \
+  --mount=type=bind,from=local/webpack-assets-previous,target=/mount/webpack-assets-previous \
   tar --no-same-owner -xf /cache-helper/webpack-runner-dependencies.tar -C ${APP_HOME} && \
-  tar --no-same-owner -xf /cache-helper/webpack-runner.tar -C ${APP_HOME}
+  tar --no-same-owner -xf /cache-helper/webpack-runner.tar -C ${APP_HOME} && \
+  { { cd /mount/webpack-assets-previous/usr/src/app && cp --parents -rf public/dist/brandable_css ${APP_HOME}; } || true; }
 
 ARG JS_BUILD_NO_UGLIFY=0
 ARG RAILS_LOAD_ALL_LOCALES=0

build/new-jenkins/docker-build-helpers.sh

@@ -8,10 +8,14 @@ function add_log {
   echo "$1" >> tmp/docker-build.log
 }
 
+function compute_hash {
+  echo "$@" | md5sum | cut -d' ' -f1
+}
+
 function compute_tags {
   local tags=$1; shift
   local cachePrefix=$1; shift
-  local cacheId=$(echo "$@" | md5sum | cut -d' ' -f1)
+  local cacheId=$(compute_hash $@)
 
   compute_tags_from_hash $tags $cachePrefix $cacheId
 }
@@ -42,6 +46,19 @@ function has_remote_tags {
   return 0
 }
 
+function image_label_eq {
+  local imageName=$1; shift
+  local labelName=$1; shift
+  local expectedValue=$1; shift
+  local actualValue=$(docker inspect $imageName --format "{{ .Config.Labels.$labelName }}")
+
+  if [[ "$actualValue" != "$expectedValue" ]]; then
+    return 1
+  fi
+
+  return 0
+}
+
 function pull_first_tag {
   local -n selectedTag=$1; shift
   local loadTags=$@

build/new-jenkins/docker-build.sh

@@ -36,7 +36,7 @@ WORKSPACE=${WORKSPACE:-$(pwd)}
 # $WEBPACK_BUILDER_TAG: additional tag for the webpack-builder image
 #   - set to patchset unique ID for builds to reference without knowing about the hash ID
 
-export CACHE_VERSION="2022-09-23.1"
+export CACHE_VERSION="2022-09-26.1"
 export DOCKER_BUILDKIT=1
 
 source ./build/new-jenkins/docker-build-helpers.sh
@@ -101,6 +101,16 @@ WEBPACK_ASSETS_PARTS=(
   $WEBPACK_ASSETS_DOCKERFILE_MD5
 )
 
+# If any of these SHAs change - we don't want to use the previously cached webpack assets to prevent the
+# cache from using stale dependencies.
+WEBPACK_ASSETS_CACHE_ID_PARTS=(
+  "${WEBPACK_BUILDER_PARTS[@]}"
+  $WEBPACK_RUNNER_DEPENDENCIES_MD5
+  $WEBPACK_RUNNER_DOCKERFILE_MD5
+  $WEBPACK_ASSETS_DOCKERFILE_MD5
+)
+WEBPACK_ASSETS_CACHE_ID=$(compute_hash ${WEBPACK_ASSETS_CACHE_ID_PARTS[@]})
+
 declare -A BASE_RUNNER_TAGS; compute_tags "BASE_RUNNER_TAGS" $BASE_RUNNER_PREFIX ${BASE_RUNNER_PARTS[@]}
 declare -A RUBY_RUNNER_TAGS; compute_tags "RUBY_RUNNER_TAGS" $RUBY_RUNNER_PREFIX ${RUBY_RUNNER_PARTS[@]}
 declare -A YARN_RUNNER_TAGS; compute_tags "YARN_RUNNER_TAGS" $YARN_RUNNER_PREFIX ${YARN_RUNNER_PARTS[@]}
@@ -172,6 +182,8 @@ if [ -z "${WEBPACK_ASSETS_SELECTED_TAG}" ]; then
     WEBPACK_BUILDER_SELECTED_TAG=${WEBPACK_BUILDER_TAGS[SAVE_TAG]}
 
     add_log "built ${WEBPACK_BUILDER_SELECTED_TAG}"
+
+    tag_many starlord.inscloudgate.net/jenkins/core:focal local/webpack-assets-previous
   else
     RUBY_RUNNER_SELECTED_TAG=$(docker inspect $WEBPACK_BUILDER_SELECTED_TAG --format '{{ .Config.Labels.RUBY_RUNNER_SELECTED_TAG }}')
     YARN_RUNNER_SELECTED_TAG=$(docker inspect $WEBPACK_BUILDER_SELECTED_TAG --format '{{ .Config.Labels.YARN_RUNNER_SELECTED_TAG }}')
@@ -183,6 +195,18 @@ if [ -z "${WEBPACK_ASSETS_SELECTED_TAG}" ]; then
 
     ./build/new-jenkins/docker-with-flakey-network-protection.sh pull $RUBY_RUNNER_SELECTED_TAG
     tag_many $RUBY_RUNNER_SELECTED_TAG local/ruby-runner ${RUBY_RUNNER_TAGS[SAVE_TAG]}
+
+    (
+      ./build/new-jenkins/docker-with-flakey-network-protection.sh pull $WEBPACK_ASSETS_FUZZY_TAG
+
+      if ! image_label_eq $WEBPACK_ASSETS_FUZZY_TAG "WEBPACK_ASSETS_CACHE_ID" $WEBPACK_ASSETS_CACHE_ID; then
+        exit 1
+      fi
+
+      tag_many $WEBPACK_ASSETS_FUZZY_TAG local/webpack-assets-previous
+    ) || (
+      tag_many starlord.inscloudgate.net/jenkins/core:focal local/webpack-assets-previous
+    )
   fi
 
   tag_many $WEBPACK_BUILDER_SELECTED_TAG local/webpack-builder ${WEBPACK_BUILDER_TAGS[SAVE_TAG]} ${WEBPACK_BUILDER_TAGS[UNIQUE_TAG]-}
@@ -194,6 +218,7 @@ if [ -z "${WEBPACK_ASSETS_SELECTED_TAG}" ]; then
 
   docker build \
     --label "RUBY_RUNNER_SELECTED_TAG=$RUBY_RUNNER_SELECTED_TAG" \
+    --label "WEBPACK_ASSETS_CACHE_ID=$WEBPACK_ASSETS_CACHE_ID" \
     --label "WEBPACK_BUILDER_SELECTED_TAG=$WEBPACK_BUILDER_SELECTED_TAG" \
     --label "YARN_RUNNER_SELECTED_TAG=$YARN_RUNNER_SELECTED_TAG" \
     --tag "${WEBPACK_ASSETS_TAGS[SAVE_TAG]}" \

build/new-jenkins/library/vars/buildDockerImageStage.groovy

@@ -170,6 +170,7 @@ def premergeCacheImage() {
 def patchsetImage(asyncStepsStr = '') {
   credentials.withStarlordCredentials {
     def cacheScope = configuration.isChangeMerged() ? env.IMAGE_CACHE_MERGE_SCOPE : env.IMAGE_CACHE_BUILD_SCOPE
+    def webpackAssetsFuzzyTag = configuration.isChangeMerged() ? "" : "${env.WEBPACK_ASSETS_PREFIX}:${getFuzzyTagSuffix()}"
 
     slackSendCacheBuild {
       withEnv([
@@ -184,6 +185,7 @@ def patchsetImage(asyncStepsStr = '') {
         "RAILS_LOAD_ALL_LOCALES=${getRailsLoadAllLocales()}",
         "RUBY_RUNNER_PREFIX=${env.RUBY_RUNNER_PREFIX}",
         "WEBPACK_BUILDER_PREFIX=${env.WEBPACK_BUILDER_PREFIX}",
+        "WEBPACK_ASSETS_FUZZY_TAG=${webpackAssetsFuzzyTag}",
         "WEBPACK_ASSETS_PREFIX=${env.WEBPACK_ASSETS_PREFIX}",
         "YARN_RUNNER_PREFIX=${env.YARN_RUNNER_PREFIX}",
       ]) {