CI: Build examples in parallel

Now you can create several 'build_examples_N' jobs
    in the .gitlab-ci.yaml and get parallel execution.

.gitlab-ci.yml

@@ -114,7 +114,7 @@ build_esp_idf_tests:
     - make print_flash_cmd | tail -n 1 > build/download.config
     - python tools/UnitTestParser.py
 
-build_examples:
+.build_examples_template: &build_examples_template
   <<: *build_template
   artifacts:
     paths:
@@ -122,15 +122,32 @@ build_examples:
       - build_examples/*/*/*/build/*.elf
       - build_examples/*/*/*/build/*.map
       - build_examples/*/*/*/build/bootloader/*.bin
-    expire_in: 6 mos
+    expire_in: 1 week
   variables:
     IDF_CI_BUILD: "1"
+    GIT_STRATEGY: fetch
   script:
     # it's not possible to build 100% out-of-tree and have the "artifacts"
     # mechanism work, but this is the next best thing
     - mkdir build_examples
     - cd build_examples
-    - ${IDF_PATH}/make/build_examples.sh
+    # build some of examples
+    - ${IDF_PATH}/make/build_examples.sh "${CI_JOB_NAME}"
+
+build_examples_00:
+  <<: *build_examples_template
+
+build_examples_01:
+  <<: *build_examples_template
+
+build_examples_02:
+  <<: *build_examples_template
+
+build_examples_03:
+  <<: *build_examples_template
+
+build_examples_04:
+  <<: *build_examples_template
 
 build_docs:
   stage: build

make/build_examples.sh

@@ -5,31 +5,107 @@
 #
 # Runs as part of CI process.
 #
-# Assumes CWD is an out-of-tree build directory, and will copy examples to individual subdirectories, one by one.
+# Assumes CWD is an out-of-tree build directory, and will copy examples
+# to individual subdirectories, one by one.
 #
-[ -z ${IDF_PATH} ] && echo "IDF_PATH is not set" && exit 1
+#
+# Without arguments it just builds all examples
+#
+# With one argument <JOB_NAME> it builds part of the examples. This is a useful for
+#   parallel execution in CI.
+#   <JOB_NAME> must look like this:
+#               <some_text_label>_<num>
+#   It scans .gitlab-ci.yaml to count number of jobs which have name "<some_text_label>_<num>"
+#   It scans the filesystem to count all examples
+#   Based on this, it decides to run qa set of examples.
+#
+
+# -----------------------------------------------------------------------------
+# Safety settings (see https://gist.github.com/ilg-ul/383869cbb01f61a51c4d).
+
+if [[ ! -z ${DEBUG} ]]
+then
+  set -x # Activate the expand mode if DEBUG is anything but empty.
+fi
+
+set -o errexit # Exit if command failed.
+set -o pipefail # Exit if pipe failed.
+set -o nounset # Exit if variable not set.
+
+# Remove the initial space and instead use '\n'.
+IFS=$'\n\t'
+
+# -----------------------------------------------------------------------------
+
+die() {
+    echo "${1:-"Unknown Error"}" 1>&2
+    exit 1
+}
+
+[ -z ${IDF_PATH} ] && die "IDF_PATH is not set"
+
+# only 0 or 1 arguments
+[ $# -le 1 ] || die "Have to run as $(basename $0) [<JOB_NAME>]"
 
 export BATCH_BUILD=1
 export V=0 # only build verbose if there's an error
 
-EXAMPLE_NUM=1
 RESULT=0
 FAILED_EXAMPLES=""
 
 RESULT_WARNINGS=22  # magic number result code for "warnings found"
 LOG_WARNINGS=$(mktemp -t example_all.XXXX.log)
 
+if [ $# -eq 0 ]
+then
+    START_NUM=0
+    END_NUM=999
+else
+    JOB_NAME=$1
+
+    # parse text prefix at the beginning of string 'some_your_text_NUM'
+    # (will be 'some_your_text' without last '_')
+    JOB_PATTERN=$( echo ${JOB_NAME} | sed -n -r 's/^(.*)_[0-9]+$/\1/p' )
+    [ -z ${JOB_PATTERN} ] && die "JOB_PATTERN is bad"
+
+    # parse number 'NUM' at the end of string 'some_your_text_NUM'
+    JOB_NUM=$( echo ${JOB_NAME} | sed -n -r 's/^.*_([0-9]+)$/\1/p' )
+    [ -z ${JOB_NUM} ] && die "JOB_NUM is bad"
+
+    # count number of the jobs
+    NUM_OF_JOBS=$( grep -c -E "^${JOB_PATTERN}_[0-9]+:$" "${IDF_PATH}/.gitlab-ci.yml" )
+    [ -z ${NUM_OF_JOBS} ] && die "NUM_OF_JOBS is bad"
+
+    # count number of examples
+    NUM_OF_EXAMPLES=$( find ${IDF_PATH}/examples/ -type f -name Makefile | wc -l )
+    [ -z ${NUM_OF_EXAMPLES} ] && die "NUM_OF_EXAMPLES is bad"
+
+    # separate intervals
+    #57 / 5 == 12
+    NUM_OF_EX_PER_JOB=$(( (${NUM_OF_EXAMPLES} + ${NUM_OF_JOBS} - 1) / ${NUM_OF_JOBS} ))
+    [ -z ${NUM_OF_EX_PER_JOB} ] && die "NUM_OF_EX_PER_JOB is bad"
+
+    # ex.: [0; 12); [12; 24); [24; 36); [36; 48); [48; 60)
+    START_NUM=$(( ${JOB_NUM} * ${NUM_OF_EX_PER_JOB} ))
+    [ -z ${START_NUM} ] && die "START_NUM is bad"
+
+    END_NUM=$(( (${JOB_NUM} + 1) * ${NUM_OF_EX_PER_JOB} ))
+    [ -z ${END_NUM} ] && die "END_NUM is bad"
+fi
+
 build_example () {
+    local ID=$1
+    shift
     local MAKE_FILE=$1
     shift
 
     local EXAMPLE_DIR=$(dirname "${MAKE_FILE}")
     local EXAMPLE_NAME=$(basename "${EXAMPLE_DIR}")
 
-    echo "Building ${EXAMPLE_NAME} as ${EXAMPLE_NUM}..."
+    echo "Building ${EXAMPLE_NAME} as ${ID}..."
-    mkdir -p "example_builds/${EXAMPLE_NUM}"
+    mkdir -p "example_builds/${ID}"
-    cp -r "${EXAMPLE_DIR}" "example_builds/${EXAMPLE_NUM}"
+    cp -r "${EXAMPLE_DIR}" "example_builds/${ID}"
-    pushd "example_builds/${EXAMPLE_NUM}/${EXAMPLE_NAME}"
+    pushd "example_builds/${ID}/${EXAMPLE_NAME}"
         # be stricter in the CI build than the default IDF settings
         export EXTRA_CFLAGS="-Werror -Werror=deprecated-declarations"
         export EXTRA_CXXFLAGS=${EXTRA_CFLAGS}
@@ -37,35 +113,42 @@ build_example () {
         # build non-verbose first
         local BUILDLOG=$(mktemp -t examplebuild.XXXX.log)
         (
-            set -o pipefail  # so result of make all isn't lost when piping to tee
-            set -e
             make clean defconfig
-            make $* all 2>&1 | tee "${BUILDLOG}"
+            make all 2>&1 | tee "${BUILDLOG}"
         ) || { RESULT=$?; FAILED_EXAMPLES+=" ${EXAMPLE_NAME}"; make V=1; } # verbose output for errors
     popd
 
-    EXAMPLE_NUM=$(( $EXAMPLE_NUM + 1 ))
-
     if grep ": warning:" "${BUILDLOG}" 2>&1 >> "${LOG_WARNINGS}"; then
         [ $RESULT -eq 0 ] && RESULT=$RESULT_WARNINGS
         FAILED_EXAMPLES+=" ${EXAMPLE_NAME} (warnings)"
     fi
 
-    grep -i error "${BUILDLOG}" 2>&1 >> "${LOG_WARNINGS}"
+    grep -i error "${BUILDLOG}" 2>&1 >> "${LOG_WARNINGS}" || :
 
     rm -f "${BUILDLOG}"
 }
 
+EXAMPLE_NUM=0
+
 find ${IDF_PATH}/examples/ -type f -name Makefile | \
-while read fn
+while read FN
 do
-    build_example "$fn" $*
+    if [[ $EXAMPLE_NUM -lt $START_NUM || $EXAMPLE_NUM -ge $END_NUM ]]
+    then
+        EXAMPLE_NUM=$(( $EXAMPLE_NUM + 1 ))
+        continue
+    fi
+    echo ">>> example [ ${EXAMPLE_NUM} ] - $FN"
+
+    build_example "${EXAMPLE_NUM}" "${FN}"
+
+    EXAMPLE_NUM=$(( $EXAMPLE_NUM + 1 ))
 done
 
 # show warnings
 echo -e "\nFound issues:"
 # pattern is: not 'error.o' and not '-Werror'
-grep -v "error.o\|\-Werror" -- "${LOG_WARNINGS}"
+grep -v "error.o\|\-Werror" -- "${LOG_WARNINGS}" || echo -e "\tNone"
 rm -f "${LOG_WARNINGS}"
 
 if [ $RESULT -eq $RESULT_WARNINGS ]; then
@@ -74,6 +157,6 @@ fi
 
 [ $RESULT -eq 0 ] || echo "Failed examples: $FAILED_EXAMPLES"
 
-echo -e "\nResult = $RESULT"
+echo -e "\nReturn code = $RESULT"
 
 exit $RESULT