Save previous run data (#600)

Automatically make the metadata from the previous run available by copying it at the start of the build. This will be used to provide better failure messages.

bin/compile

@@ -134,6 +134,10 @@ install_bins() {
   bd_set "npm-version-request" "$npm_engine"
   bd_set "yarn-version-request" "$yarn_engine"
 
+  bd_set "node-version-request" "$node_engine"
+  bd_set "npm-version-request" "$npm_engine"
+  bd_set "yarn-version-request" "$yarn_engine"
+
   if [ -n "$iojs_engine" ]; then
     echo "engines.iojs (package.json):  $iojs_engine (iojs)"
   else

lib/build-data.sh

@@ -2,10 +2,18 @@
 
 # variable shared by this whole module
 BUILD_DATA_FILE=""
+PREVIOUS_BUILD_DATA_FILE=""
 
 bd_create() {
   local cache_dir="$1"
-  BUILD_DATA_FILE="$cache_dir/build-data/node"
+  BUILD_DATA_FILE="$cache_dir/build-data/nodejs"
+  PREVIOUS_BUILD_DATA_FILE="$cache_dir/build-data/nodejs-prev"
+
+  # if the file already exists because it's from the last build, save it
+  if [[ -f "$BUILD_DATA_FILE" ]]; then
+    cp "$BUILD_DATA_FILE" "$PREVIOUS_BUILD_DATA_FILE"
+  fi
+
   kv_create "$BUILD_DATA_FILE"
   # make sure this doesnt grow over time
   kv_clear "$BUILD_DATA_FILE"
@@ -29,6 +37,26 @@ bd_time() {
   kv_set "$BUILD_DATA_FILE" "$key" "$time"
 }
 
+# similar to mtime from stdlib
+bd_time() {
+  local key="$1"
+  local start="$2"
+  local end="${3:-$(nowms)}"
+  local time
+  time="$(echo "$start" "$end" | awk '{ printf "%.3f", ($2 - $1)/1000 }')"
+  kv_set "$BUILD_DATA_FILE" "$1" "$time"
+}
+
+# Retrieve a value from a previous build if it exists
+# This is useful to give the user context about what changed if the 
+# build has failed. Ex:
+#   - changed stacks
+#   - deployed with a new major version of Node
+#   - etc
+bd_prev_get() {
+  kv_get "$PREVIOUS_BUILD_DATA_FILE" "$1"
+}
+
 log_build_data() {
   # print all values on one line in logfmt format
   # https://brandur.org/logfmt

lib/dependencies.sh

@@ -80,6 +80,11 @@ log_build_scripts() {
   bd_set "heroku-prebuild-script" "$heroku_prebuild"
   bd_set "heroku-postbuild-script" "$heroku_prebuild"
 
+  bd_set "build-script" "$build"
+  bd_set "postinstall-script" "$postinstall"
+  bd_set "heroku-prebuild-script" "$heroku_prebuild"
+  bd_set "heroku-postbuild-script" "$heroku_prebuild"
+
   if [ -n "$build" ]; then
     mcount "scripts.build"
 

test/unit

@@ -180,6 +180,44 @@ testBuildData() {
   assertEquals "30.002" "$(bd_get time)"
 }
 
+testBuildDataPreviousBuild() {
+  local cache_dir=$(mktemp -d)
+
+  # the first time, there will be no previous build file
+  bd_create "$cache_dir"
+  assertContains "nodejs" "$BUILD_DATA_FILE"
+  assertContains "nodejs-prev" "$PREVIOUS_BUILD_DATA_FILE"
+  assertFileExists "$BUILD_DATA_FILE"
+
+  # set a value in the build data file
+  bd_set "test" "foo"
+  assertFileContains "test=foo" "$BUILD_DATA_FILE"
+  assertFileDoesNotExist "$PREVIOUS_BUILD_DATA_FILE"
+
+  assertEquals "$(bd_get test)" "foo"
+  assertEquals "$(bd_prev_get test)" ""
+
+  # the second time this is called (cache restored)
+  # there will be a previous build file
+  bd_create "$cache_dir"
+  assertFileExists "$BUILD_DATA_FILE"
+  assertFileExists "$PREVIOUS_BUILD_DATA_FILE"
+
+  # the data stored in the previous build should now be in the second file
+  assertFileNotContains "test=foo" "$BUILD_DATA_FILE"
+  assertFileContains "test=foo" "$PREVIOUS_BUILD_DATA_FILE"
+  assertEquals "$(bd_get test)" ""
+  assertEquals "$(bd_prev_get test)" "foo"
+  bd_set "test" "bar"
+
+  # doing it once more does not result in an error
+  bd_create "$cache_dir"
+  assertFileExists "$BUILD_DATA_FILE"
+  assertFileExists "$PREVIOUS_BUILD_DATA_FILE" 
+  assertEquals "$(bd_prev_get test)" "bar"
+  assertEquals "$(bd_get test)" ""
+}
+
 testWebConcurrencyProfileScript() {
   # this was set when we sourced the WEB_CONCURRENCY.sh file
   unset WEB_MEMORY
@@ -232,5 +270,8 @@ source "$(pwd)"/lib/kvstore.sh
 source "$(pwd)"/lib/build-data.sh
 source "$(pwd)"/profile/WEB_CONCURRENCY.sh
 
+# testing utils
+source "$(pwd)"/test/utils
+
 # import the testing framework
 source "$(pwd)"/test/shunit2