investigate: snapshot propagation latency degrades non-linearly under concurrent watchers (5th flake at maxForks=2 + 10s budget) #175

Closed
Closed
investigate: snapshot propagation latency degrades non-linearly under concurrent watchers (5th flake at maxForks=2 + 10s budget)#175
Labels
bugSomething isn't workingpriority-normal

Description

@moonming
moonming
opened on May 9, 2026

Summary

The harness-level fixes shipped in #169 (`waitConfigPropagation` 5s→10s + `maxForks` 4→2) did not eliminate the recurring flake on `guardrail-keyword-e2e.test.ts`. 5th occurrence observed on PR #172's CI (post-#169 rebase): `waitConfigPropagation: condition not met within 10s`.

RunmaxForksbudgetOutcome
1 (original #157)45sflake
2 (#165)45sflake
3 (#167)45sflake
4 (#169 own first attempt)410sflake (motivated maxForks→2 escalation)
5 (#172, post-#169 rebase)210sflake

Pattern

  • Failure is concentrated on `guardrail-keyword-e2e.test.ts` — the test that gates readiness on the last resource in a 4-resource setup batch (Model + ApiKey + ProviderKey + Guardrail).
  • Infra knobs (lower parallelism, longer budget) reduce frequency but don't eliminate it.
  • Even at maxForks=2 with 10s budget, propagation latency for the trailing Guardrail resource exceeds the budget.

This pattern strongly supports the product-side hypothesis that #157 noted as deferred:

Real product slowness — the gateway's snapshot propagation queue under N concurrent watch streams from N gateway instances could have a contention bug. Worth investigating whether propagation latency degrades non-linearly with concurrent watcher count.

Possible product-side root causes (need investigation)

  1. Lock contention in the snapshot reload path. When the gateway receives an etcd watch event, does the snapshot reload acquire a write-lock that blocks readers? Under N concurrent gateway instances → N watch streams → N times the lock-pressure on the shared etcd's revision dispatch loop.

  2. etcd revision-stream serialization across concurrent `Watch()` RPCs. etcd processes watch events in a single goroutine per stream; multiple streams against the same etcd may share contention on the underlying boltdb. Worth measuring per-revision dispatch latency under load.

  3. Per-resource-type sequential application. If the gateway applies a multi-resource batch one resource at a time and re-builds the entire snapshot between each resource (rather than batching), the LAST resource (Guardrail) lands after Model + ApiKey + ProviderKey have each triggered N rebuilds. With 4 resources and N=2 gateways, that's 8 rebuilds before Guardrail is visible.

  4. Watch-event coalescing dropped. etcd allows server-side coalescing of watch events; if the gateway's client doesn't coalesce, every revision triggers a full snapshot reload. Under load that's O(N × revisions) reloads.

Suggested investigation path

  1. Add OTLP / Prom counters for "snapshot propagation latency by resource type" — measure 95th/99th percentile under `maxForks=2` and `maxForks=4` runs.
  2. Add a stress test that spawns N=8 `aisix` instances against one etcd, each writing a 4-resource batch and timing snapshot-visibility for the LAST resource. Compare N=1 vs N=2 vs N=4 vs N=8 propagation latency.
  3. If latency degrades super-linearly with N, that's the product bug; if linear-only, the harness budget needs further bump but no product change.

Workaround if root-cause takes time

If a product-side fix is too involved to ship quickly, the harness could:

  • Bump `waitConfigPropagation` deadline further (10s→20s or 30s).
  • Force `singleFork: true` in vitest config (sequential e2e files, eliminates concurrency entirely — slower but deterministic).
  • Refactor `guardrail-keyword-e2e.test.ts` to register the Guardrail resource FIRST (before Model + ApiKey + ProviderKey), so propagation completion of the last resource is no longer the load-bearing readiness signal.

Severity

MEDIUM as a product concern (only affects observed CI flakiness, no production data loss); HIGH as a CI-velocity concern (5 reruns burned on this same flake).

Audit trail

Surfaced cumulatively across #156, #165, #167, #169 (own first run), #172. The hypothesis was flagged as a LOW audit finding on #169 ("symptomatic fix; product-side hypothesis still open"). With 5 occurrences across 5 PRs, the hypothesis warrants product-side investigation rather than further harness band-aids.

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      , 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
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}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

      Skip to content
      investigate: snapshot propagation latency degrades non-linearly under concurrent watchers (5th flake at maxForks=2 + 10s budget) #175
      Closed
      Closed
      investigate: snapshot propagation latency degrades non-linearly under concurrent watchers (5th flake at maxForks=2 + 10s budget)#175
      Labels
      bugSomething isn't workingpriority-normal
      Description
      @moonming
      moonming
      opened on May 9, 2026
      Summary
      The harness-level fixes shipped in #169 (`waitConfigPropagation` 5s→10s + `maxForks` 4→2) did not eliminate the recurring flake on `guardrail-keyword-e2e.test.ts`. 5th occurrence observed on PR #172's CI (post-#169 rebase): `waitConfigPropagation: condition not met within 10s`.
      RunmaxForksbudgetOutcome
      1 (original #157)45sflake
      2 (#165)45sflake
      3 (#167)45sflake
      4 (#169 own first attempt)410sflake (motivated maxForks→2 escalation)
      5 (#172, post-#169 rebase)210sflake
      Pattern
      • Failure is concentrated on `guardrail-keyword-e2e.test.ts` — the test that gates readiness on the last resource in a 4-resource setup batch (Model + ApiKey + ProviderKey + Guardrail).
      • Infra knobs (lower parallelism, longer budget) reduce frequency but don't eliminate it.
      • Even at maxForks=2 with 10s budget, propagation latency for the trailing Guardrail resource exceeds the budget.
      This pattern strongly supports the product-side hypothesis that #157 noted as deferred:
      Real product slowness — the gateway's snapshot propagation queue under N concurrent watch streams from N gateway instances could have a contention bug. Worth investigating whether propagation latency degrades non-linearly with concurrent watcher count.
      Possible product-side root causes (need investigation)
      1. Lock contention in the snapshot reload path. When the gateway receives an etcd watch event, does the snapshot reload acquire a write-lock that blocks readers? Under N concurrent gateway instances → N watch streams → N times the lock-pressure on the shared etcd's revision dispatch loop.
      2. etcd revision-stream serialization across concurrent `Watch()` RPCs. etcd processes watch events in a single goroutine per stream; multiple streams against the same etcd may share contention on the underlying boltdb. Worth measuring per-revision dispatch latency under load.
      3. Per-resource-type sequential application. If the gateway applies a multi-resource batch one resource at a time and re-builds the entire snapshot between each resource (rather than batching), the LAST resource (Guardrail) lands after Model + ApiKey + ProviderKey have each triggered N rebuilds. With 4 resources and N=2 gateways, that's 8 rebuilds before Guardrail is visible.
      4. Watch-event coalescing dropped. etcd allows server-side coalescing of watch events; if the gateway's client doesn't coalesce, every revision triggers a full snapshot reload. Under load that's O(N × revisions) reloads.
      Suggested investigation path
      1. Add OTLP / Prom counters for "snapshot propagation latency by resource type" — measure 95th/99th percentile under `maxForks=2` and `maxForks=4` runs.
      2. Add a stress test that spawns N=8 `aisix` instances against one etcd, each writing a 4-resource batch and timing snapshot-visibility for the LAST resource. Compare N=1 vs N=2 vs N=4 vs N=8 propagation latency.
      3. If latency degrades super-linearly with N, that's the product bug; if linear-only, the harness budget needs further bump but no product change.
      Workaround if root-cause takes time
      If a product-side fix is too involved to ship quickly, the harness could:
      • Bump `waitConfigPropagation` deadline further (10s→20s or 30s).
      • Force `singleFork: true` in vitest config (sequential e2e files, eliminates concurrency entirely — slower but deterministic).
      • Refactor `guardrail-keyword-e2e.test.ts` to register the Guardrail resource FIRST (before Model + ApiKey + ProviderKey), so propagation completion of the last resource is no longer the load-bearing readiness signal.
      Severity
      MEDIUM as a product concern (only affects observed CI flakiness, no production data loss); HIGH as a CI-velocity concern (5 reruns burned on this same flake).
      Audit trail
      Surfaced cumulatively across #156, #165, #167, #169 (own first run), #172. The hypothesis was flagged as a LOW audit finding on #169 ("symptomatic fix; product-side hypothesis still open"). With 5 occurrences across 5 PRs, the hypothesis warrants product-side investigation rather than further harness band-aids.
      Metadata
      Metadata
      Assignees
      No one assigned
        Labels
        bugSomething isn't workingpriority-normal
        Type
        No type
        Projects
        No projects
          Milestone
          No milestone
          Relationships
          None yet
          Development
          No branches or pull requests
          Issue actions
          
, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
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})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

          Skip to content
          investigate: snapshot propagation latency degrades non-linearly under concurrent watchers (5th flake at maxForks=2 + 10s budget) #175
          Closed
          Closed
          investigate: snapshot propagation latency degrades non-linearly under concurrent watchers (5th flake at maxForks=2 + 10s budget)#175
          Labels
          bugSomething isn't workingpriority-normal
          Description
          @moonming
          moonming
          opened on May 9, 2026
          Summary
          The harness-level fixes shipped in #169 (`waitConfigPropagation` 5s→10s + `maxForks` 4→2) did not eliminate the recurring flake on `guardrail-keyword-e2e.test.ts`. 5th occurrence observed on PR #172's CI (post-#169 rebase): `waitConfigPropagation: condition not met within 10s`.
          RunmaxForksbudgetOutcome
          1 (original #157)45sflake
          2 (#165)45sflake
          3 (#167)45sflake
          4 (#169 own first attempt)410sflake (motivated maxForks→2 escalation)
          5 (#172, post-#169 rebase)210sflake
          Pattern
          • Failure is concentrated on `guardrail-keyword-e2e.test.ts` — the test that gates readiness on the last resource in a 4-resource setup batch (Model + ApiKey + ProviderKey + Guardrail).
          • Infra knobs (lower parallelism, longer budget) reduce frequency but don't eliminate it.
          • Even at maxForks=2 with 10s budget, propagation latency for the trailing Guardrail resource exceeds the budget.
          This pattern strongly supports the product-side hypothesis that #157 noted as deferred:
          Real product slowness — the gateway's snapshot propagation queue under N concurrent watch streams from N gateway instances could have a contention bug. Worth investigating whether propagation latency degrades non-linearly with concurrent watcher count.
          Possible product-side root causes (need investigation)
          1. Lock contention in the snapshot reload path. When the gateway receives an etcd watch event, does the snapshot reload acquire a write-lock that blocks readers? Under N concurrent gateway instances → N watch streams → N times the lock-pressure on the shared etcd's revision dispatch loop.
          2. etcd revision-stream serialization across concurrent `Watch()` RPCs. etcd processes watch events in a single goroutine per stream; multiple streams against the same etcd may share contention on the underlying boltdb. Worth measuring per-revision dispatch latency under load.
          3. Per-resource-type sequential application. If the gateway applies a multi-resource batch one resource at a time and re-builds the entire snapshot between each resource (rather than batching), the LAST resource (Guardrail) lands after Model + ApiKey + ProviderKey have each triggered N rebuilds. With 4 resources and N=2 gateways, that's 8 rebuilds before Guardrail is visible.
          4. Watch-event coalescing dropped. etcd allows server-side coalescing of watch events; if the gateway's client doesn't coalesce, every revision triggers a full snapshot reload. Under load that's O(N × revisions) reloads.
          Suggested investigation path
          1. Add OTLP / Prom counters for "snapshot propagation latency by resource type" — measure 95th/99th percentile under `maxForks=2` and `maxForks=4` runs.
          2. Add a stress test that spawns N=8 `aisix` instances against one etcd, each writing a 4-resource batch and timing snapshot-visibility for the LAST resource. Compare N=1 vs N=2 vs N=4 vs N=8 propagation latency.
          3. If latency degrades super-linearly with N, that's the product bug; if linear-only, the harness budget needs further bump but no product change.
          Workaround if root-cause takes time
          If a product-side fix is too involved to ship quickly, the harness could:
          • Bump `waitConfigPropagation` deadline further (10s→20s or 30s).
          • Force `singleFork: true` in vitest config (sequential e2e files, eliminates concurrency entirely — slower but deterministic).
          • Refactor `guardrail-keyword-e2e.test.ts` to register the Guardrail resource FIRST (before Model + ApiKey + ProviderKey), so propagation completion of the last resource is no longer the load-bearing readiness signal.
          Severity
          MEDIUM as a product concern (only affects observed CI flakiness, no production data loss); HIGH as a CI-velocity concern (5 reruns burned on this same flake).
          Audit trail
          Surfaced cumulatively across #156, #165, #167, #169 (own first run), #172. The hypothesis was flagged as a LOW audit finding on #169 ("symptomatic fix; product-side hypothesis still open"). With 5 occurrences across 5 PRs, the hypothesis warrants product-side investigation rather than further harness band-aids.
          Metadata
          Metadata
          Assignees
          No one assigned
            Labels
            bugSomething isn't workingpriority-normal
            Type
            No type
            Projects
            No projects
              Milestone
              No milestone
              Relationships
              None yet
              Development
              No branches or pull requests
              Issue actions
              
, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

              Skip to content
              investigate: snapshot propagation latency degrades non-linearly under concurrent watchers (5th flake at maxForks=2 + 10s budget) #175
              Closed
              Closed
              investigate: snapshot propagation latency degrades non-linearly under concurrent watchers (5th flake at maxForks=2 + 10s budget)#175
              Labels
              bugSomething isn't workingpriority-normal
              Description
              @moonming
              moonming
              opened on May 9, 2026
              Summary
              The harness-level fixes shipped in #169 (`waitConfigPropagation` 5s→10s + `maxForks` 4→2) did not eliminate the recurring flake on `guardrail-keyword-e2e.test.ts`. 5th occurrence observed on PR #172's CI (post-#169 rebase): `waitConfigPropagation: condition not met within 10s`.
              RunmaxForksbudgetOutcome
              1 (original #157)45sflake
              2 (#165)45sflake
              3 (#167)45sflake
              4 (#169 own first attempt)410sflake (motivated maxForks→2 escalation)
              5 (#172, post-#169 rebase)210sflake
              Pattern
              • Failure is concentrated on `guardrail-keyword-e2e.test.ts` — the test that gates readiness on the last resource in a 4-resource setup batch (Model + ApiKey + ProviderKey + Guardrail).
              • Infra knobs (lower parallelism, longer budget) reduce frequency but don't eliminate it.
              • Even at maxForks=2 with 10s budget, propagation latency for the trailing Guardrail resource exceeds the budget.
              This pattern strongly supports the product-side hypothesis that #157 noted as deferred:
              Real product slowness — the gateway's snapshot propagation queue under N concurrent watch streams from N gateway instances could have a contention bug. Worth investigating whether propagation latency degrades non-linearly with concurrent watcher count.
              Possible product-side root causes (need investigation)
              1. Lock contention in the snapshot reload path. When the gateway receives an etcd watch event, does the snapshot reload acquire a write-lock that blocks readers? Under N concurrent gateway instances → N watch streams → N times the lock-pressure on the shared etcd's revision dispatch loop.
              2. etcd revision-stream serialization across concurrent `Watch()` RPCs. etcd processes watch events in a single goroutine per stream; multiple streams against the same etcd may share contention on the underlying boltdb. Worth measuring per-revision dispatch latency under load.
              3. Per-resource-type sequential application. If the gateway applies a multi-resource batch one resource at a time and re-builds the entire snapshot between each resource (rather than batching), the LAST resource (Guardrail) lands after Model + ApiKey + ProviderKey have each triggered N rebuilds. With 4 resources and N=2 gateways, that's 8 rebuilds before Guardrail is visible.
              4. Watch-event coalescing dropped. etcd allows server-side coalescing of watch events; if the gateway's client doesn't coalesce, every revision triggers a full snapshot reload. Under load that's O(N × revisions) reloads.
              Suggested investigation path
              1. Add OTLP / Prom counters for "snapshot propagation latency by resource type" — measure 95th/99th percentile under `maxForks=2` and `maxForks=4` runs.
              2. Add a stress test that spawns N=8 `aisix` instances against one etcd, each writing a 4-resource batch and timing snapshot-visibility for the LAST resource. Compare N=1 vs N=2 vs N=4 vs N=8 propagation latency.
              3. If latency degrades super-linearly with N, that's the product bug; if linear-only, the harness budget needs further bump but no product change.
              Workaround if root-cause takes time
              If a product-side fix is too involved to ship quickly, the harness could:
              • Bump `waitConfigPropagation` deadline further (10s→20s or 30s).
              • Force `singleFork: true` in vitest config (sequential e2e files, eliminates concurrency entirely — slower but deterministic).
              • Refactor `guardrail-keyword-e2e.test.ts` to register the Guardrail resource FIRST (before Model + ApiKey + ProviderKey), so propagation completion of the last resource is no longer the load-bearing readiness signal.
              Severity
              MEDIUM as a product concern (only affects observed CI flakiness, no production data loss); HIGH as a CI-velocity concern (5 reruns burned on this same flake).
              Audit trail
              Surfaced cumulatively across #156, #165, #167, #169 (own first run), #172. The hypothesis was flagged as a LOW audit finding on #169 ("symptomatic fix; product-side hypothesis still open"). With 5 occurrences across 5 PRs, the hypothesis warrants product-side investigation rather than further harness band-aids.
              Metadata
              Metadata
              Assignees
              No one assigned
                Labels
                bugSomething isn't workingpriority-normal
                Type
                No type
                Projects
                No projects
                  Milestone
                  No milestone
                  Relationships
                  None yet
                  Development
                  No branches or pull requests
                  Issue actions
                  
, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

                  Skip to content
                  investigate: snapshot propagation latency degrades non-linearly under concurrent watchers (5th flake at maxForks=2 + 10s budget) #175
                  Closed
                  Closed
                  investigate: snapshot propagation latency degrades non-linearly under concurrent watchers (5th flake at maxForks=2 + 10s budget)#175
                  Labels
                  bugSomething isn't workingpriority-normal
                  Description
                  @moonming
                  moonming
                  opened on May 9, 2026
                  Summary
                  The harness-level fixes shipped in #169 (`waitConfigPropagation` 5s→10s + `maxForks` 4→2) did not eliminate the recurring flake on `guardrail-keyword-e2e.test.ts`. 5th occurrence observed on PR #172's CI (post-#169 rebase): `waitConfigPropagation: condition not met within 10s`.
                  RunmaxForksbudgetOutcome
                  1 (original #157)45sflake
                  2 (#165)45sflake
                  3 (#167)45sflake
                  4 (#169 own first attempt)410sflake (motivated maxForks→2 escalation)
                  5 (#172, post-#169 rebase)210sflake
                  Pattern
                  • Failure is concentrated on `guardrail-keyword-e2e.test.ts` — the test that gates readiness on the last resource in a 4-resource setup batch (Model + ApiKey + ProviderKey + Guardrail).
                  • Infra knobs (lower parallelism, longer budget) reduce frequency but don't eliminate it.
                  • Even at maxForks=2 with 10s budget, propagation latency for the trailing Guardrail resource exceeds the budget.
                  This pattern strongly supports the product-side hypothesis that #157 noted as deferred:
                  Real product slowness — the gateway's snapshot propagation queue under N concurrent watch streams from N gateway instances could have a contention bug. Worth investigating whether propagation latency degrades non-linearly with concurrent watcher count.
                  Possible product-side root causes (need investigation)
                  1. Lock contention in the snapshot reload path. When the gateway receives an etcd watch event, does the snapshot reload acquire a write-lock that blocks readers? Under N concurrent gateway instances → N watch streams → N times the lock-pressure on the shared etcd's revision dispatch loop.
                  2. etcd revision-stream serialization across concurrent `Watch()` RPCs. etcd processes watch events in a single goroutine per stream; multiple streams against the same etcd may share contention on the underlying boltdb. Worth measuring per-revision dispatch latency under load.
                  3. Per-resource-type sequential application. If the gateway applies a multi-resource batch one resource at a time and re-builds the entire snapshot between each resource (rather than batching), the LAST resource (Guardrail) lands after Model + ApiKey + ProviderKey have each triggered N rebuilds. With 4 resources and N=2 gateways, that's 8 rebuilds before Guardrail is visible.
                  4. Watch-event coalescing dropped. etcd allows server-side coalescing of watch events; if the gateway's client doesn't coalesce, every revision triggers a full snapshot reload. Under load that's O(N × revisions) reloads.
                  Suggested investigation path
                  1. Add OTLP / Prom counters for "snapshot propagation latency by resource type" — measure 95th/99th percentile under `maxForks=2` and `maxForks=4` runs.
                  2. Add a stress test that spawns N=8 `aisix` instances against one etcd, each writing a 4-resource batch and timing snapshot-visibility for the LAST resource. Compare N=1 vs N=2 vs N=4 vs N=8 propagation latency.
                  3. If latency degrades super-linearly with N, that's the product bug; if linear-only, the harness budget needs further bump but no product change.
                  Workaround if root-cause takes time
                  If a product-side fix is too involved to ship quickly, the harness could:
                  • Bump `waitConfigPropagation` deadline further (10s→20s or 30s).
                  • Force `singleFork: true` in vitest config (sequential e2e files, eliminates concurrency entirely — slower but deterministic).
                  • Refactor `guardrail-keyword-e2e.test.ts` to register the Guardrail resource FIRST (before Model + ApiKey + ProviderKey), so propagation completion of the last resource is no longer the load-bearing readiness signal.
                  Severity
                  MEDIUM as a product concern (only affects observed CI flakiness, no production data loss); HIGH as a CI-velocity concern (5 reruns burned on this same flake).
                  Audit trail
                  Surfaced cumulatively across #156, #165, #167, #169 (own first run), #172. The hypothesis was flagged as a LOW audit finding on #169 ("symptomatic fix; product-side hypothesis still open"). With 5 occurrences across 5 PRs, the hypothesis warrants product-side investigation rather than further harness band-aids.
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                  No one assigned
                    Labels
                    bugSomething isn't workingpriority-normal
                    Type
                    No type
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                    No projects
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                      No milestone
                      Relationships
                      None yet
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

                      Skip to content
                      investigate: snapshot propagation latency degrades non-linearly under concurrent watchers (5th flake at maxForks=2 + 10s budget) #175
                      Closed
                      Closed
                      investigate: snapshot propagation latency degrades non-linearly under concurrent watchers (5th flake at maxForks=2 + 10s budget)#175
                      Labels
                      bugSomething isn't workingpriority-normal
                      Description
                      @moonming
                      moonming
                      opened on May 9, 2026
                      Summary
                      The harness-level fixes shipped in #169 (`waitConfigPropagation` 5s→10s + `maxForks` 4→2) did not eliminate the recurring flake on `guardrail-keyword-e2e.test.ts`. 5th occurrence observed on PR #172's CI (post-#169 rebase): `waitConfigPropagation: condition not met within 10s`.
                      RunmaxForksbudgetOutcome
                      1 (original #157)45sflake
                      2 (#165)45sflake
                      3 (#167)45sflake
                      4 (#169 own first attempt)410sflake (motivated maxForks→2 escalation)
                      5 (#172, post-#169 rebase)210sflake
                      Pattern
                      • Failure is concentrated on `guardrail-keyword-e2e.test.ts` — the test that gates readiness on the last resource in a 4-resource setup batch (Model + ApiKey + ProviderKey + Guardrail).
                      • Infra knobs (lower parallelism, longer budget) reduce frequency but don't eliminate it.
                      • Even at maxForks=2 with 10s budget, propagation latency for the trailing Guardrail resource exceeds the budget.
                      This pattern strongly supports the product-side hypothesis that #157 noted as deferred:
                      Real product slowness — the gateway's snapshot propagation queue under N concurrent watch streams from N gateway instances could have a contention bug. Worth investigating whether propagation latency degrades non-linearly with concurrent watcher count.
                      Possible product-side root causes (need investigation)
                      1. Lock contention in the snapshot reload path. When the gateway receives an etcd watch event, does the snapshot reload acquire a write-lock that blocks readers? Under N concurrent gateway instances → N watch streams → N times the lock-pressure on the shared etcd's revision dispatch loop.
                      2. etcd revision-stream serialization across concurrent `Watch()` RPCs. etcd processes watch events in a single goroutine per stream; multiple streams against the same etcd may share contention on the underlying boltdb. Worth measuring per-revision dispatch latency under load.
                      3. Per-resource-type sequential application. If the gateway applies a multi-resource batch one resource at a time and re-builds the entire snapshot between each resource (rather than batching), the LAST resource (Guardrail) lands after Model + ApiKey + ProviderKey have each triggered N rebuilds. With 4 resources and N=2 gateways, that's 8 rebuilds before Guardrail is visible.
                      4. Watch-event coalescing dropped. etcd allows server-side coalescing of watch events; if the gateway's client doesn't coalesce, every revision triggers a full snapshot reload. Under load that's O(N × revisions) reloads.
                      Suggested investigation path
                      1. Add OTLP / Prom counters for "snapshot propagation latency by resource type" — measure 95th/99th percentile under `maxForks=2` and `maxForks=4` runs.
                      2. Add a stress test that spawns N=8 `aisix` instances against one etcd, each writing a 4-resource batch and timing snapshot-visibility for the LAST resource. Compare N=1 vs N=2 vs N=4 vs N=8 propagation latency.
                      3. If latency degrades super-linearly with N, that's the product bug; if linear-only, the harness budget needs further bump but no product change.
                      Workaround if root-cause takes time
                      If a product-side fix is too involved to ship quickly, the harness could:
                      • Bump `waitConfigPropagation` deadline further (10s→20s or 30s).
                      • Force `singleFork: true` in vitest config (sequential e2e files, eliminates concurrency entirely — slower but deterministic).
                      • Refactor `guardrail-keyword-e2e.test.ts` to register the Guardrail resource FIRST (before Model + ApiKey + ProviderKey), so propagation completion of the last resource is no longer the load-bearing readiness signal.
                      Severity
                      MEDIUM as a product concern (only affects observed CI flakiness, no production data loss); HIGH as a CI-velocity concern (5 reruns burned on this same flake).
                      Audit trail
                      Surfaced cumulatively across #156, #165, #167, #169 (own first run), #172. The hypothesis was flagged as a LOW audit finding on #169 ("symptomatic fix; product-side hypothesis still open"). With 5 occurrences across 5 PRs, the hypothesis warrants product-side investigation rather than further harness band-aids.
                      Metadata
                      Metadata
                      Assignees
                      No one assigned
                        Labels
                        bugSomething isn't workingpriority-normal
                        Type
                        No type
                        Projects
                        No projects
                          Milestone
                          No milestone
                          Relationships
                          None yet
                          Development
                          No branches or pull requests
                          Issue actions
                          
, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

                          Skip to content
                          investigate: snapshot propagation latency degrades non-linearly under concurrent watchers (5th flake at maxForks=2 + 10s budget) #175
                          Closed
                          Closed
                          investigate: snapshot propagation latency degrades non-linearly under concurrent watchers (5th flake at maxForks=2 + 10s budget)#175
                          Labels
                          bugSomething isn't workingpriority-normal
                          Description
                          @moonming
                          moonming
                          opened on May 9, 2026
                          Summary
                          The harness-level fixes shipped in #169 (`waitConfigPropagation` 5s→10s + `maxForks` 4→2) did not eliminate the recurring flake on `guardrail-keyword-e2e.test.ts`. 5th occurrence observed on PR #172's CI (post-#169 rebase): `waitConfigPropagation: condition not met within 10s`.
                          RunmaxForksbudgetOutcome
                          1 (original #157)45sflake
                          2 (#165)45sflake
                          3 (#167)45sflake
                          4 (#169 own first attempt)410sflake (motivated maxForks→2 escalation)
                          5 (#172, post-#169 rebase)210sflake
                          Pattern
                          • Failure is concentrated on `guardrail-keyword-e2e.test.ts` — the test that gates readiness on the last resource in a 4-resource setup batch (Model + ApiKey + ProviderKey + Guardrail).
                          • Infra knobs (lower parallelism, longer budget) reduce frequency but don't eliminate it.
                          • Even at maxForks=2 with 10s budget, propagation latency for the trailing Guardrail resource exceeds the budget.
                          This pattern strongly supports the product-side hypothesis that #157 noted as deferred:
                          Real product slowness — the gateway's snapshot propagation queue under N concurrent watch streams from N gateway instances could have a contention bug. Worth investigating whether propagation latency degrades non-linearly with concurrent watcher count.
                          Possible product-side root causes (need investigation)
                          1. Lock contention in the snapshot reload path. When the gateway receives an etcd watch event, does the snapshot reload acquire a write-lock that blocks readers? Under N concurrent gateway instances → N watch streams → N times the lock-pressure on the shared etcd's revision dispatch loop.
                          2. etcd revision-stream serialization across concurrent `Watch()` RPCs. etcd processes watch events in a single goroutine per stream; multiple streams against the same etcd may share contention on the underlying boltdb. Worth measuring per-revision dispatch latency under load.
                          3. Per-resource-type sequential application. If the gateway applies a multi-resource batch one resource at a time and re-builds the entire snapshot between each resource (rather than batching), the LAST resource (Guardrail) lands after Model + ApiKey + ProviderKey have each triggered N rebuilds. With 4 resources and N=2 gateways, that's 8 rebuilds before Guardrail is visible.
                          4. Watch-event coalescing dropped. etcd allows server-side coalescing of watch events; if the gateway's client doesn't coalesce, every revision triggers a full snapshot reload. Under load that's O(N × revisions) reloads.
                          Suggested investigation path
                          1. Add OTLP / Prom counters for "snapshot propagation latency by resource type" — measure 95th/99th percentile under `maxForks=2` and `maxForks=4` runs.
                          2. Add a stress test that spawns N=8 `aisix` instances against one etcd, each writing a 4-resource batch and timing snapshot-visibility for the LAST resource. Compare N=1 vs N=2 vs N=4 vs N=8 propagation latency.
                          3. If latency degrades super-linearly with N, that's the product bug; if linear-only, the harness budget needs further bump but no product change.
                          Workaround if root-cause takes time
                          If a product-side fix is too involved to ship quickly, the harness could:
                          • Bump `waitConfigPropagation` deadline further (10s→20s or 30s).
                          • Force `singleFork: true` in vitest config (sequential e2e files, eliminates concurrency entirely — slower but deterministic).
                          • Refactor `guardrail-keyword-e2e.test.ts` to register the Guardrail resource FIRST (before Model + ApiKey + ProviderKey), so propagation completion of the last resource is no longer the load-bearing readiness signal.
                          Severity
                          MEDIUM as a product concern (only affects observed CI flakiness, no production data loss); HIGH as a CI-velocity concern (5 reruns burned on this same flake).
                          Audit trail
                          Surfaced cumulatively across #156, #165, #167, #169 (own first run), #172. The hypothesis was flagged as a LOW audit finding on #169 ("symptomatic fix; product-side hypothesis still open"). With 5 occurrences across 5 PRs, the hypothesis warrants product-side investigation rather than further harness band-aids.
                          Metadata
                          Metadata
                          Assignees
                          No one assigned
                            Labels
                            bugSomething isn't workingpriority-normal
                            Type
                            No type
                            Projects
                            No projects
                              Milestone
                              No milestone
                              Relationships
                              None yet
                              Development
                              No branches or pull requests
                              Issue actions
                              
, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

                              Skip to content
                              investigate: snapshot propagation latency degrades non-linearly under concurrent watchers (5th flake at maxForks=2 + 10s budget) #175
                              Closed
                              Closed
                              investigate: snapshot propagation latency degrades non-linearly under concurrent watchers (5th flake at maxForks=2 + 10s budget)#175
                              Labels
                              bugSomething isn't workingpriority-normal
                              Description
                              @moonming
                              moonming
                              opened on May 9, 2026
                              Summary
                              The harness-level fixes shipped in #169 (`waitConfigPropagation` 5s→10s + `maxForks` 4→2) did not eliminate the recurring flake on `guardrail-keyword-e2e.test.ts`. 5th occurrence observed on PR #172's CI (post-#169 rebase): `waitConfigPropagation: condition not met within 10s`.
                              RunmaxForksbudgetOutcome
                              1 (original #157)45sflake
                              2 (#165)45sflake
                              3 (#167)45sflake
                              4 (#169 own first attempt)410sflake (motivated maxForks→2 escalation)
                              5 (#172, post-#169 rebase)210sflake
                              Pattern
                              • Failure is concentrated on `guardrail-keyword-e2e.test.ts` — the test that gates readiness on the last resource in a 4-resource setup batch (Model + ApiKey + ProviderKey + Guardrail).
                              • Infra knobs (lower parallelism, longer budget) reduce frequency but don't eliminate it.
                              • Even at maxForks=2 with 10s budget, propagation latency for the trailing Guardrail resource exceeds the budget.
                              This pattern strongly supports the product-side hypothesis that #157 noted as deferred:
                              Real product slowness — the gateway's snapshot propagation queue under N concurrent watch streams from N gateway instances could have a contention bug. Worth investigating whether propagation latency degrades non-linearly with concurrent watcher count.
                              Possible product-side root causes (need investigation)
                              1. Lock contention in the snapshot reload path. When the gateway receives an etcd watch event, does the snapshot reload acquire a write-lock that blocks readers? Under N concurrent gateway instances → N watch streams → N times the lock-pressure on the shared etcd's revision dispatch loop.
                              2. etcd revision-stream serialization across concurrent `Watch()` RPCs. etcd processes watch events in a single goroutine per stream; multiple streams against the same etcd may share contention on the underlying boltdb. Worth measuring per-revision dispatch latency under load.
                              3. Per-resource-type sequential application. If the gateway applies a multi-resource batch one resource at a time and re-builds the entire snapshot between each resource (rather than batching), the LAST resource (Guardrail) lands after Model + ApiKey + ProviderKey have each triggered N rebuilds. With 4 resources and N=2 gateways, that's 8 rebuilds before Guardrail is visible.
                              4. Watch-event coalescing dropped. etcd allows server-side coalescing of watch events; if the gateway's client doesn't coalesce, every revision triggers a full snapshot reload. Under load that's O(N × revisions) reloads.
                              Suggested investigation path
                              1. Add OTLP / Prom counters for "snapshot propagation latency by resource type" — measure 95th/99th percentile under `maxForks=2` and `maxForks=4` runs.
                              2. Add a stress test that spawns N=8 `aisix` instances against one etcd, each writing a 4-resource batch and timing snapshot-visibility for the LAST resource. Compare N=1 vs N=2 vs N=4 vs N=8 propagation latency.
                              3. If latency degrades super-linearly with N, that's the product bug; if linear-only, the harness budget needs further bump but no product change.
                              Workaround if root-cause takes time
                              If a product-side fix is too involved to ship quickly, the harness could:
                              • Bump `waitConfigPropagation` deadline further (10s→20s or 30s).
                              • Force `singleFork: true` in vitest config (sequential e2e files, eliminates concurrency entirely — slower but deterministic).
                              • Refactor `guardrail-keyword-e2e.test.ts` to register the Guardrail resource FIRST (before Model + ApiKey + ProviderKey), so propagation completion of the last resource is no longer the load-bearing readiness signal.
                              Severity
                              MEDIUM as a product concern (only affects observed CI flakiness, no production data loss); HIGH as a CI-velocity concern (5 reruns burned on this same flake).
                              Audit trail
                              Surfaced cumulatively across #156, #165, #167, #169 (own first run), #172. The hypothesis was flagged as a LOW audit finding on #169 ("symptomatic fix; product-side hypothesis still open"). With 5 occurrences across 5 PRs, the hypothesis warrants product-side investigation rather than further harness band-aids.
                              Metadata
                              Metadata
                              Assignees
                              No one assigned
                                Labels
                                bugSomething isn't workingpriority-normal
                                Type
                                No type
                                Projects
                                No projects
                                  Milestone
                                  No milestone
                                  Relationships
                                  None yet
                                  Development
                                  No branches or pull requests
                                  Issue actions