diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml index c3dcff2..4c0b51a 100644 --- a/.github/workflows/ci.yml +++ b/.github/workflows/ci.yml @@ -314,13 +314,16 @@ jobs: name: E2E (API 37 preview) runs-on: ubuntu-latest timeout-minutes: 35 - # SPIKE / PoC (docs/perf/api37-e2e-sharding-spike.md) — DRAFT, DO NOT MERGE AS-IS. - # Shards the instrumented suite across N parallel API 37 emulators (each a separate matrix leg - # that hand-provisions its OWN emulator and runs one shard via AndroidJUnitRunner numShards/ - # shardIndex). Projected: ~17.1 min -> ~12.7 min (N=2), cutting the pipeline's critical path - # ~28%. `ci-passed` still lists `e2e-preview` once; GHA rolls all shard legs under it (a matrix - # job's result is `failure` if any shard fails), so no branch-protection change is needed. - # Keep API37_NUM_SHARDS in lockstep with the length of matrix.shard. + # Sharded N=2 (docs/perf/api37-e2e-sharding-spike.md). The instrumented suite is split across + # 2 parallel API 37 emulators — each a separate matrix leg that hand-provisions its OWN emulator + # and runs one shard via AndroidJUnitRunner's numShards/shardIndex. This leg is the pipeline's + # critical path, so sharding cuts it ~17.1 min -> ~12.7 min (~28% off total CI) for +1 emulator + # job. FAN-IN: `ci-passed` lists `e2e-preview` once and GHA rolls BOTH shard legs under that one + # entry — a matrix job's aggregate result is `failure` if ANY leg fails — so both shards must + # pass, and branch protection (which requires the "CI passed" context, not the per-leg + # "E2E (API 37 preview) (N)" names) needs no change. `fail-fast: false` lets one shard's failure + # NOT cancel the other, so both reports always upload. Keep API37_NUM_SHARDS in lockstep with the + # length of matrix.shard. strategy: fail-fast: false matrix: @@ -439,8 +442,8 @@ jobs: return 1 } - # SPIKE: start the adb daemon up-front (mirror api37_e2e.py wait_for_boot) so attempt 1 - # can't lose the adb-server "Address already in use" bind race that flaked #370's boot. + # Start the adb daemon up-front (mirrors api37_e2e.py wait_for_boot) so attempt 1 can't + # lose the adb-server "Address already in use" bind race that flaked #370's boot. adb start-server || true booted=0 @@ -448,21 +451,21 @@ jobs: [ "$booted" = "1" ] || { echo "::error::API 37 preview emulator failed to boot after 2 attempts"; exit 1; } adb shell input keyevent 82 || true - # SPIKE: run only this matrix leg's shard. AndroidJUnitRunner hashes each test name into - # one of numShards buckets and runs only shardIndex's bucket. The args flow through AGP's - # -Pandroid.testInstrumentationRunnerArguments.* channel (same one local_instrumented.py + # Run only this matrix leg's shard. AndroidJUnitRunner hashes each test name into one of + # numShards buckets and runs only shardIndex's bucket. The args flow through AGP's + # -Pandroid.testInstrumentationRunnerArguments.* channel (the same one local_instrumented.py # uses for .class=…) — no GMD, no orchestrator, no Gradle-side change. run_shard() { ./gradlew connectedDebugAndroidTest --stacktrace \ "-Pandroid.testInstrumentationRunnerArguments.numShards=${API37_NUM_SHARDS}" \ "-Pandroid.testInstrumentationRunnerArguments.shardIndex=${{ matrix.shard }}" } - # SPIKE: retry this shard's test run ONCE on failure — retry parity with the stable `e2e` - # matrix (which retries once, so a flaky test self-heals on API 29–36 but wedges the - # required gate on API 37 today, e.g. #370). Per-shard, so the retry re-runs only this - # shard's ~T/N tests, not the whole suite. MITIGATION, NOT A FIX: a blanket retry also - # masks genuine regressions, so the retried-but-passed case is flagged as a ::warning:: - # and the real fix stays test-level. See docs/perf/api37-e2e-sharding-spike.md. + # Retry this shard's test run ONCE on failure — retry parity with the stable `e2e` matrix + # (which retries once, so a flaky test self-heals on API 29–36 but would otherwise wedge + # the required gate on API 37, e.g. #370). Per-shard, so the retry re-runs only this shard's + # ~T/N tests, not the whole suite. MITIGATION, NOT A FIX: a blanket retry also masks genuine + # regressions, so the retried-but-passed case is flagged as a ::warning:: and the real fix + # stays test-level. See docs/perf/api37-e2e-sharding-spike.md. run_shard || { echo "::warning::API 37 shard ${{ matrix.shard }} test run failed — retrying once"; run_shard; } - name: Dump emulator log on failure @@ -477,7 +480,7 @@ jobs: if: always() uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1 with: - # SPIKE: shard-unique name — upload-artifact@v7 errors on duplicate artifact names. + # Shard-unique name — upload-artifact@v7 errors on duplicate artifact names. name: e2e-api37-boot-diagnostics-shard${{ matrix.shard }} path: | ${{ runner.temp }}/emulator.log @@ -493,7 +496,7 @@ jobs: if: ${{ !cancelled() }} uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1 with: - # SPIKE: shard-unique name — upload-artifact@v7 errors on duplicate artifact names. + # Shard-unique name — upload-artifact@v7 errors on duplicate artifact names. name: e2e-test-report-api37-preview-shard${{ matrix.shard }} path: app/build/reports/androidTests/connected/ if-no-files-found: warn diff --git a/docs/perf/api37-e2e-sharding-spike.md b/docs/perf/api37-e2e-sharding-spike.md index 28378ec..f551fc0 100644 --- a/docs/perf/api37-e2e-sharding-spike.md +++ b/docs/perf/api37-e2e-sharding-spike.md @@ -1,22 +1,27 @@ -# API 37 preview E2E sharding — feasibility spike +# API 37 preview E2E sharding — adopted at N=2 -A time-boxed investigation into whether **sharding the `e2e-preview` job** (the hand-provisioned -API 37 / `google_apis_ps16k` 16 KB-page emulator that runs the whole instrumented suite serially) -would meaningfully cut CI wall-clock. `e2e-preview` is **consistently the single longest leg in CI** -(~16.4–17.6 min on recent runs), so it sets the pipeline's critical path. +**Status: ADOPTED (N=2).** `e2e-preview` is sharded across 2 parallel API 37 emulators in +`.github/workflows/ci.yml`. This document is the design + measurement record behind that change: it +began as a time-boxed feasibility spike (should we shard the hand-provisioned API 37 / +`google_apis_ps16k` 16 KB-page emulator that ran the whole instrumented suite serially?) and now +records the adopted design. `e2e-preview` was **consistently the single longest leg in CI** +(~16.4–17.6 min on recent runs), so it set the pipeline's critical path. -This is an **assessment + recommendation**, not a finished feature. It was produced from CI run logs -and repo config only — **no emulator was booted locally** (avoids the machine-freeze risk noted in the -project memory and runner contention). All numbers below come from real successful `e2e-preview` runs. +The analysis below was produced from CI run logs and repo config only — **no emulator was booted +locally** (avoids the machine-freeze risk noted in the project memory and runner contention). All +numbers come from real successful `e2e-preview` runs; the PR's own CI run validates the live 2-shard +timings and that both shards gate `ci-passed`. ## TL;DR / recommendation -**GO — shard `e2e-preview` in CI at `N = 2`** (a `strategy.matrix.shard: [1, 2]` fan-out, each shard -provisioning its own API 37 emulator and running one half of the suite via AndroidJUnitRunner's built-in -`numShards`/`shardIndex`). Projected: the leg drops from **~17.1 min → ~12.7 min**, cutting the whole -pipeline's critical path by **~4.9 min (~28%)** for the cost of **+1 emulator job (~1.5× this leg's -emulator-minutes)**. +**ADOPTED — `e2e-preview` is sharded in CI at `N = 2`** (a `strategy.matrix.shard: [0, 1]` fan-out — +the values are **0-based** `shardIndex`es — each shard provisioning its own API 37 emulator and running +one half of the suite via AndroidJUnitRunner's built-in `numShards`/`shardIndex`). Projected: the leg +drops from **~17.1 min → ~12.7 min**, cutting the whole pipeline's critical path by **~4.9 min (~28%)** +for the cost of **+1 emulator job (~1.5× this leg's emulator-minutes)**. Two reliability fixes ship with +it: per-shard **test-retry parity** with the stable `e2e` matrix and an **`adb start-server`** before the +boot loop (§5.9 / §6). - **`N = 3` is a defensible stretch** (~11.2 min) but buys only ~0.7 min more of *total-CI* time, because at that point the **rest of the E2E matrix (API 30, ~12.0 min) becomes the new critical path**. The @@ -65,7 +70,7 @@ Sharding only parallelizes **test execution**; every shard re-pays boot **and** - **`T` (parallelizable test execution) ≈ 8.8 min** - **`B` (fixed, re-paid by every shard) ≈ 8.3 min** -i.e. **B ≈ T** — roughly a 50/50 split. That is the single most important number in this spike: because +i.e. **B ≈ T** — roughly a 50/50 split. That is the single most important number in this analysis: because the fixed overhead is about as large as the test time, sharding has a **hard floor of ~8.3 min** no matter how many shards you add. @@ -107,10 +112,12 @@ hand-provisioned `connectedDebugAndroidTest`** (no GMD required) each shard runs ```bash ./gradlew connectedDebugAndroidTest \ -Pandroid.testInstrumentationRunnerArguments.numShards=2 \ - -Pandroid.testInstrumentationRunnerArguments.shardIndex=${{ matrix.shard-index }} + -Pandroid.testInstrumentationRunnerArguments.shardIndex=${{ matrix.shard }} ``` -Wrapped in a `strategy.matrix.shard: [1, 2]` (or `[1, 2, 3]`) fan-out where each matrix leg provisions its +`shardIndex` is **0-based** (a bucket in `0..numShards-1`), so the matrix values are `[0, 1]`, **not** +`[1, 2]` — `shardIndex=numShards` would run an empty bucket and silently drop half the suite. +Wrapped in a `strategy.matrix.shard: [0, 1]` (or `[0, 1, 2]`) fan-out where each matrix leg provisions its **own** API 37 emulator and runs one shard. This is the same fan-in pattern the repo **already uses** for the `e2e` (API 29–36) matrix, and the same runner-arg channel `local_instrumented.py` already uses for `…arguments.class=` — so it is a known-good mechanism here, needs **no orchestrator, no Gradle-side change, @@ -217,39 +224,41 @@ min (API 30 ≈ 12.0 is its ceiling)**. So the API 37 leg only helps the pipelin strictly cheaper than the unsharded whole-suite retry (`B + T`). So sharding makes flake-recovery both still-necessary and *cheaper*. **Framing: mitigation, not a fix** — a blanket retry also masks genuine regressions, so surface the retried-but-passed case as a `::warning::` and keep the real fix test-level - (as #370 does). See §6 for the recommendation and the PoC. + (as #370 does). See §6 for the recommendation and the implementation. -## 6. Recommendation +## 6. Recommendation (adopted) -**Worth doing: yes.** `e2e-preview` is the pipeline's critical path, so unlike #258 (unit tests, which finish -~8.5 min *inside* the E2E-bounded gate and were correctly closed as not-worthwhile) sharding this leg +**Worth doing: yes — done.** `e2e-preview` is the pipeline's critical path, so unlike #258 (unit tests, which +finish ~8.5 min *inside* the E2E-bounded gate and were correctly closed as not-worthwhile) sharding this leg **directly** shortens total CI. -- **Ship `N = 2`** via a `strategy.matrix.shard` fan-out using AndroidJUnitRunner `numShards`/`shardIndex` - (§3a). Expected total-CI critical path **~17.6 → ~12.7 min (~28% off)** for **+1 emulator job**. Keep the - per-shard two-attempt boot loop; suffix shard index on the report/diagnostics artifact names; leave - `e2e-preview` in `ci-passed.needs` (matrix fan-in keeps the single gate). -- **`N = 3` optional** only if the last ~0.7 min matters and runner headroom is comfortable — it moves the - critical path onto the API 30 matrix leg (~12.0 min). **Never `N ≥ 4`** without also sharding the API 29–36 - matrix. +- **Adopted `N = 2`** via a `strategy.matrix.shard: [0, 1]` fan-out using AndroidJUnitRunner + `numShards`/`shardIndex` (§3a). Expected total-CI critical path **~17.6 → ~12.7 min (~28% off)** for **+1 + emulator job**. Each shard keeps the two-attempt boot loop; the report/diagnostics artifact names carry the + shard index; `e2e-preview` stays a single entry in `ci-passed.needs` (matrix fan-in keeps the single gate — + both shards must pass; §5.3). `fail-fast: false` so a failing shard doesn't cancel its sibling. +- **`N = 3` not adopted** — reserved for if the last ~0.7 min ever matters and runner headroom is comfortable; + it moves the critical path onto the API 30 matrix leg (~12.0 min). **Never `N ≥ 4`** without also sharding + the API 29–36 matrix. - **Local preflight stays single-emulator** — `api37_e2e.py` and `local_instrumented.py` keep their single - hand-provisioned boot (do **not** shard locally). One free hypervisor per dev box; parallel local emulators - risk freezing the machine (project memory). The sharding divergence is intentional and should be documented - in the job comment. + hand-provisioned boot (not sharded). One free hypervisor per dev box; parallel local emulators risk freezing + the machine (project memory). The sharding divergence is intentional and is documented in the job comment. -Two **reliability** fixes to pair with sharding (from the #370 root-cause; §5 item 9) — together they make -the API 37 leg *faster **and** more reliable*: +Two **reliability** fixes ship with sharding (from the #370 root-cause; §5 item 9) — together they make the +API 37 leg *faster **and** more reliable*: -- **Add retry parity.** Give `e2e-preview` the **same single test-run retry** the `e2e` matrix has, as a - **per-shard** retry (re-runs only that shard's `B + T/N`, not the whole suite), and **mirror it into the - local `api37_e2e.py`** test-run step (its `connectedDebugAndroidTest` invocation) so preflight and CI stay - in lockstep. **This is a mitigation, not a fix:** a blanket retry masks genuine regressions, so flag the - retried-but-passed case as a warning and keep real flakes fixed at the test level (as #370 did). Do **not** - raise the retry count above one. *Sharding interaction:* a per-shard retry is the natural fit and is - cheaper than an unsharded retry — see §5 item 9. -- **Minor: `adb start-server` before the boot loop** in `e2e-preview` (mirror `api37_e2e.py`'s - `wait_for_boot`, which already does this), to avoid the attempt-1 adb-daemon "Address already in use" bind - race seen in #370 (self-recovered there; low priority, but free to harden). +- **Retry parity — shipped (CI).** `e2e-preview` now gives each shard the **same single test-run retry** the + `e2e` matrix has, as a **per-shard** retry (re-runs only that shard's tests, not the whole suite). **This is + a mitigation, not a fix:** a blanket retry masks genuine regressions, so the retried-but-passed case is + flagged as a `::warning::` and real flakes stay fixed at the test level (as #370 did). The retry count is + **one**, not more. *Sharding interaction:* a per-shard retry is the natural fit and is cheaper than an + unsharded retry — see §5 item 9. **Local mirror deferred:** mirroring the same single test-retry into + `api37_e2e.py`'s `connectedDebugAndroidTest` step (for CI/local lockstep) is a small follow-up, kept out of + this change because it can't be validated without booting a local emulator (which this change deliberately + does not do). `api37_e2e.py` already matches CI on the boot-retry loop and `adb start-server`. +- **`adb start-server` before the boot loop — shipped (CI).** Mirrors `api37_e2e.py`'s `wait_for_boot` (which + already does this), avoiding the attempt-1 adb-daemon "Address already in use" bind race seen in #370 + (self-recovered there; free hardening). ### Relationship to #258 (unit-test sharding) @@ -260,16 +269,20 @@ so the conclusion flips to GO. **Distinct from #258:** different layer (on-devic different mechanism (`numShards`/`shardIndex` matrix vs `maxParallelForks`), and **no coverage-merge constraint** (instrumented coverage is out of scope), which makes this strictly simpler to land. -## PoC +## Implementation -This branch carries a **draft, non-auto-merged** PoC that converts `e2e-preview` to an `N = 2` shard matrix -(clearly marked as a spike). It also folds in the two §6 reliability fixes on the CI side so the PoC shows -the full *faster + more reliable* picture: a **per-shard single test retry** (retry parity with the `e2e` -matrix, flagged `::warning::` on the retried-but-passed case) and an **`adb start-server` before the boot -loop**. The matching `api37_e2e.py` retry mirror is left as a documented recommendation (a focused local -change, since the local path is validated by a real emulator, which this spike deliberately did not boot). +This change converts `e2e-preview` to an `N = 2` shard matrix (`strategy.matrix.shard: [0, 1]`, +`fail-fast: false`), each leg hand-provisioning its own API 37 emulator and running one shard via +`-Pandroid.testInstrumentationRunnerArguments.numShards=2 -Pandroid.testInstrumentationRunnerArguments.shardIndex=<0|1>`. +Each uploaded artifact name carries the shard index (`…-shard${{ matrix.shard }}`) — `upload-artifact@v7` +errors on duplicate names. It also folds in the two §6 reliability fixes on the CI side: a **per-shard single +test retry** (retry parity with the `e2e` matrix, flagged `::warning::` on the retried-but-passed case) and +an **`adb start-server` before the boot loop**. The matching `api37_e2e.py` local retry mirror is a +documented follow-up (§6) — not bundled here because it can't be validated without booting a local emulator. -Because a PR runs the workflow *from its own branch*, **the draft PR's own CI run is the validation** — the -maintainer can confirm both shards go green and read the real per-shard wall-clock straight off that run -(this is a CI-infra change, so a green pipeline is the "test", per #258's DoD note). It is **not** to be -merged as-is: adopt after reviewing the live shard timings and confirming runner headroom. +**Validation.** Because a PR runs the workflow *from its own branch*, **this PR's own CI run is the +validation** — both shards must go green and the real per-shard wall-clock is readable straight off that run +(this is a CI-infra change, so a green pipeline is the "test", per #258's DoD note). Both shards fan into the +single `e2e-preview` entry in `ci-passed.needs`; GHA's matrix aggregation makes `e2e-preview`'s result +`failure` if either shard fails, so `ci-passed` (the branch-protection-required "CI passed" context) stays +red unless **both** shards pass — no branch-protection change needed (§5.3).