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[DON-2137] Spike: Parallelize CI build workflow #2522

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Merged
peterliu (peterInTown) merged 6 commits into from
Jan 9, 2026
Merged

[DON-2137] Spike: Parallelize CI build workflow #2522

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26f4a05
[DON-2137] Parallelize CI build workflow
peterInTown Dec 12, 2025
dbc28ae
Parallelize screenshot tests by variant and combine Detekt & Lint
peterInTown Dec 16, 2025
5b6b422
Improve screenshot merging with loop and error handling
peterInTown Dec 16, 2025
0fe9373
[DON-1112] rename job
peterInTown Dec 16, 2025
743d137
Use matrix strategy to eliminate screenshot job duplication
peterInTown Dec 16, 2025
28151c8
[DON-2137] address comment
peterInTown Jan 9, 2026
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140 changes: 118 additions & 22 deletions .github/workflows/_build.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -18,10 +18,54 @@ env:

jobs:

Build:
name: Build
# ============================================
# PARALLEL JOB GROUP 1: Static Analysis & Tests
# These jobs run independently and in parallel
# ============================================

StaticAnalysis:
name: DetektAndLint
runs-on: ubuntu-24.04-16cores-public
timeout-minutes: 30
timeout-minutes: 15

steps:
- uses: actions/checkout@v6

- name: Set up JDK
uses: actions/setup-java@v5
with:
java-version: '17'
distribution: 'adopt'
cache: gradle

- name: Detekt check
run: ./gradlew detekt -PdisablePreDex

- name: Lint check
run: ./gradlew lint${{ env.flavour }}${{ env.config }} -PdisablePreDex

UnitTests:
name: Unit Tests
runs-on: ubuntu-24.04-16cores-public
timeout-minutes: 15

steps:
- uses: actions/checkout@v6

- name: Set up JDK
uses: actions/setup-java@v5
with:
java-version: '17'
distribution: 'adopt'
cache: gradle

- name: Unit Tests
run: ./gradlew test${{ env.flavour }}${{ env.config }}UnitTest -PdisablePreDex

BuildAndTokens:
name: Build & Tokens
runs-on: ubuntu-24.04-16cores-public
timeout-minutes: 20
permissions:
statuses: write
pull-requests: write
Expand Down Expand Up @@ -96,14 +140,10 @@ jobs:
git diff-index --quiet HEAD || git commit -m "Update tokens"
git push

- name: Detekt check
run: ./gradlew detekt -PdisablePreDex

- name: Lint check
run: ./gradlew lint${{ env.flavour }}${{ env.config }} -PdisablePreDex

- name: Unit Tests
run: ./gradlew test${{ env.flavour }}${{ env.config }}UnitTest -PdisablePreDex
# ============================================
# PARALLEL JOB GROUP 2: Instrumented Tests
# These jobs also run in parallel with Group 1
# ============================================

Android:
name: Android tests
Expand Down Expand Up @@ -169,13 +209,59 @@ jobs:

./gradlew :Backpack:connected${{ env.config }}AndroidTest :backpack-compose:connected${{ env.config }}AndroidTest :backpack-common:connected${{ env.config }}AndroidTest && killall -INT crashpad_handler || true

# ============================================
# Screenshot Tests - Parallelized by Variant
# Each variant runs independently to reduce wall-clock time
# Using matrix strategy to eliminate duplication
# ============================================

Screenshots:
name: Screenshots tests
name: Screenshots (${{ matrix.variant.name }})
runs-on: ubuntu-24.04-16cores-public
timeout-minutes: 10
strategy:
matrix:
variant:
- name: default
flag: default
- name: dark mode
flag: dm
- name: RTL
flag: rtl
- name: themed
flag: themed
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@LokmaneKrizou Lokmane Krizou (LokmaneKrizou) Jan 8, 2026

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Not a blocker
Is there a way to make this dynamic, instead of setting all variants manually could we read existing variants in the repo and extract the variant names

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@peterInTown peterliu (peterInTown) Jan 9, 2026

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It is possible to extract variant from BpkTestVariant. However:
Trade-offs:

  • Pro: Single source of truth (the Kotlin enum)
  • Pro: Automatically picks up new variants
  • Con: Adds complexity and another job dependency
  • Con: Harder to debug when something goes wrong
  • Con: The merge step (line 290) would also need to be updated to be dynamic
  • Con: Less explicit - harder to see what variants run at a glance

My recommendation:
Keep it hardcoded for now. The variants rarely change (4 variants in the entire project history), and the explicit list makes the workflow easier to understand and debug. The maintenance burden of keeping two lists in
sync is minimal compared to the complexity of parsing Kotlin in bash.

steps:
- name: Checkout
uses: actions/checkout@v6

- name: Set up JDK
uses: actions/setup-java@v5
with:
java-version: '17'
distribution: 'adopt'
cache: gradle

- name: Screenshot Tests - ${{ matrix.variant.name }}
run: |
set -e
rm -rf app/screenshots/oss
./gradlew app:recordRoborazziOssDebug -Dvariant=${{ matrix.variant.flag }}

- name: Upload Screenshots
uses: actions/upload-artifact@v4
with:
name: screenshots-${{ matrix.variant.flag }}
path: app/screenshots/
retention-days: 1

Screenshots-Collect:
name: Collect & commit screenshots
runs-on: ubuntu-24.04-16cores-public
needs: Screenshots
permissions:
pull-requests: write
contents: write
timeout-minutes: 20
timeout-minutes: 5
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@LokmaneKrizou Lokmane Krizou (LokmaneKrizou) Jan 8, 2026 •
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Are we confident about dropping the timeout to 5 minutes? That’s a pretty aggressive reduction (20 → 5). If we’re confident that, after splitting, each job will consistently finish within 5 minutes, then I’m happy to keep it.

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@peterInTown peterliu (peterInTown) Jan 9, 2026

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Why 5 minutes should be sufficient:

  • This job doesn't run any tests or builds - it only downloads and merges artifacts
  • Artifact downloads are typically fast on GitHub Actions
  • File operations are simple bash commands (mkdir, cp, rm)
  • The previous 20-minute timeout was likely inherited from when this job also ran the actual screenshot tests

Why it was safe to reduce:

  • The actual screenshot tests now run in parallel in the separate Screenshots matrix job (which has 10-minute timeout)
  • The collect job only does I/O operations, which are much faster than running tests
  • Even with network delays, 5 minutes provides a ~3-4x safety margin for this type of work

steps:
- uses: actions/create-github-app-token@v2
id: app-token
Expand All @@ -188,18 +274,28 @@ jobs:
with:
token: ${{ steps.app-token.outputs.token }}

- name: Set up JDK
uses: actions/setup-java@v5
- name: Download all screenshot artifacts
uses: actions/download-artifact@v4
with:
java-version: '17'
distribution: 'adopt'
cache: gradle
path: screenshot-artifacts

- name: Screenshot Tests
id: screenshotTests
- name: Merge screenshot results
id: mergeScreenshots
run: |
set -e
./scripts/record_screenshot_tests.sh
rm -rf app/screenshots/oss
mkdir -p app/screenshots/oss

# Copy all screenshots from artifacts with error checking
for variant in default dm rtl themed; do
artifact_dir="screenshot-artifacts/screenshots-$variant/oss"
if [ -d "$artifact_dir" ] && compgen -G "$artifact_dir/*" > /dev/null; then
echo "Copying screenshots for variant: $variant"
cp -r "$artifact_dir"/* app/screenshots/oss/
else
echo "Warning: No screenshots found for variant: $variant"
fi
done

changedFiles=`git status --porcelain` && echo "CHANGED_FILES=${changedFiles//$'\n'/'%0A'}" >> $GITHUB_OUTPUT

Expand All @@ -209,7 +305,7 @@ jobs:
run: ./scripts/check-no-changes.sh

- name: Commit changes
if: ${{ github.event_name == 'pull_request' && steps.screenshotTests.outputs.CHANGED_FILES != '' }}
if: ${{ github.event_name == 'pull_request' && steps.mergeScreenshots.outputs.CHANGED_FILES != '' }}
run: |
git config --local user.email "197108191+skyscanner-backpack-bot[bot]@users.noreply.github.com"
git config --local user.name "skyscanner-backpack-bot[bot]"
Expand Down