Add read-replica routing for Perfherder read-only endpoints#9528
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Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Routes 10 read-only Perfherder viewsets to the read replica (PerformanceSignatureViewSet, PerformancePlatformViewSet, PerformanceJobViewSet, PerformanceDatumViewSet, PerformanceBugTemplateViewSet, PerformanceIssueTrackerViewSet, PerformanceSummary, PerformanceAlertSummaryTasks, PerfCompareResults, TestSuiteHealthViewSet). Adds integration tests for signature list and summary endpoints. Updates test_perfcompare_api.py, test_performance_data_api.py, and test_performance_bug_template_api.py to declare read_replica database access. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Two review fixes: 1. When the kill switch is off (READ_REPLICA_ENABLED=false or READ_REPLICA_DATABASE_URL unset), the mixin previously still wrapped dispatch, set the thread-local (a no-op without a router), and would emit a misleading "db_routing_fallback" log on any primary failure. The mixin now checks connections.databases for the alias and bypasses wrapping when absent. 2. The three test files that gained databases=["default","read_replica"] implicitly relied on fixtures pulling in transactional_db. Make the transactional requirement explicit with transaction=True so the behavior survives future fixture refactors. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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## master #9528 +/- ##
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+ Coverage 82.75% 82.84% +0.08%
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| into reading from the ``read_replica`` database alias. The router only routes | ||
| models whose Django app label is in :data:`READ_REPLICA_APP_ALLOW_LIST`. | ||
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| Design: .claude/plans/READ_REPLICA_DESIGN.md |
| The router and mixin are then active in dev. Routing is a no-op unless an | ||
| endpoint opts in via `ReadReplicaMixin`; see | ||
| `treeherder/config/db_routing.py` and the design at | ||
| `.claude/plans/READ_REPLICA_DESIGN.md`. |
| _RecordingView.raise_on_call = 0 | ||
| _RecordingView.call_count = 0 | ||
| _RecordingView.saw_use_replica = [] | ||
| yield |
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What's the benefit of this?
The feature is a no-op locally with the default .env (both env vars unset → no read_replica alias → mixin early-returns). Standard local dev doesn't need to know about the routing. The design, code-level docstring, and PR deploy notes cover the cases that do. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Successful replica routing was previously silent — only the fallback path emitted a log line. Adds a single DEBUG-level log per routed request so a developer (or ops) can grep \`db_routing routed_to=read_replica\` to confirm which requests hit the replica. Prod-silent by default (logger threshold is INFO); enable locally with LOGGING_LEVEL=DEBUG. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
Routes 11 read-only Perfherder GET endpoints through a separate
read_replicaPostgreSQL connection to relieve write-side contention on the primary database. Gated behind two env vars (READ_REPLICA_DATABASE_URL+READ_REPLICA_ENABLED) so it ships as a no-op until ops flips the switch.ReadReplicaRouter(DjangoDATABASE_ROUTERS) routes reads to the replica only when a thread-local flag is set and the model's app label is in an explicit allow-list ({"perf", "model"}).ReadReplicaMixinflips that flag forGET/HEAD/OPTIONSonly, on a one-shot retry against primary if the replica raisesOperationalError/InterfaceError, and emits adb_routing_fallbackwarning log. The mixin is a true no-op when the alias isn't configured.treeherder/webapp/api/performance_data.py. The 3 mutating viewsets (PerformanceAlertSummaryViewSet,PerformanceAlertViewSet,PerformanceTagViewSet) are intentionally left on primary so create→read flows stay consistent.Design doc:
.claude/plans/READ_REPLICA_DESIGN.md(local). Mechanism is reusable — applying it to Logviewer / Intermittent Failures View later is a one-line viewset change each.Test plan
CaptureQueriesContextasserting the replica alias actually serves opted-in endpoints and does NOT serve excluded ones — 4 tests.READ_REPLICA_DATABASE_URLin stage; flipREAD_REPLICA_ENABLED=true; soak; watchdb_routing_fallbacklog volume + primary DB CPU; then prod.READ_REPLICA_ENABLED=false(one env-var flip) and verify all routed endpoints continue returning correct data via primary.🤖 Generated with Claude Code