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fix(mount): startup splay and process-wide full-pull read cap - #521
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Mounts started in the same instant (scheduled sandboxes at cron boundaries, scoped siblings in one process) ran their first, possibly full-tree, reconcile immediately and in lockstep. Scoped layouts also run one Syncer per remote path, each with its own 4-worker bootstrap pool, so N scopes issued 4N concurrent reads against the single-threaded workspace Durable Object. - relayfile-mount: --startup-jitter / RELAYFILE_MOUNT_STARTUP_JITTER (default 5s, max 5m, 0 disables) delays the first cycle by a uniform random amount; cancellation during the splay stops cleanly (and fails --once, which has not bootstrapped). - mountsync: a process-wide gate caps in-flight full-pull reads (tree pages, bulk reads, bootstrap point reads, export snapshots) at 4 across all Syncers (RELAYFILE_FULL_PULL_READ_CONCURRENCY, max 16). Waiting honours ctx, so a timed-out cycle yields exactly as before. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com> Session-Id: 04a50716-3a69-4bf5-b6b2-7696cd1021cd
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Included review availability: This review used your included allowance. Your plan provides up to 1 included review per hour; 0 remain after this review. 📝 WalkthroughWalkthroughBoth mount commands now support a configurable delay before the first sync. Full-pull reads now use a process-wide concurrency gate with a configurable limit. ChangesStartup splay
Full-pull read concurrency
Priority: ⬇️ Low Estimated code review effort: 3 (Moderate) | ~25 minutes Change: Bug fix Sequence Diagram(s)sequenceDiagram
participant Syncer
participant fullPullReadGate
participant GitHubAPI
Syncer->>fullPullReadGate: Submit remote read with context
fullPullReadGate->>GitHubAPI: Run manifest, export, tree-listing, or file read
GitHubAPI-->>fullPullReadGate: Return read result
fullPullReadGate-->>Syncer: Return result and release slot
Merge Risk: ⚪ Minimal · up to The bounded startup delay and shared read limit are mergeable after normal checks. No concrete blocking issue remains identified. Security Architecture ReviewSecurity architecture risk: 🔵 Low · up to The change reduces synchronized read bursts without adding a new access mechanism. One bounded failure-isolation concern remains: waiting for shared read capacity can also delay a mount’s local writeback processing. Some security and recovery coverage remains incomplete. Retained concerns
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🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
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Inline comments:
Review comments at @cmd/relayfile-mount/startup_splay_test.go:
- Line 72: Update the startup-splay test to inject a fixed delay longer than its
context deadline, so the test does not depend on a random sample or
request-cycle outcome to determine whether it waited. Locate the test around the
`err == nil` check and assert the wait using the injected delay.
Review comments at @internal/mountsync/fullpull_gate_test.go:
- Line 43: Update the concurrency-limit test around `client.maxActiveRead` to
install a four-slot gate before starting the Syncers, independent of the
package-initialized environment setting. Save the previous gate and restore it
with `t.Cleanup` so the test remains isolated.
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cmd/relayfile-mount/main.gocmd/relayfile-mount/startup_splay_test.gointernal/mountsync/fullpull_gate.gointernal/mountsync/fullpull_gate_test.gointernal/mountsync/syncer.go
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The GitHub working-tree seed read its clone manifest outside fullPullReadGate and released nothing for its tar export, whose body is streamed after the request returns. N GitHub scopes seeding together therefore ran N unbounded manifest reads and tar streams on top of the four gated tree/bulk reads. - Gate the clone-manifest read. - Hold one slot from the tar export request until its body is closed (readGate.acquire returns an idempotent release). - Tests install their own gate (withFullPullReadGate) so the cap assertion no longer depends on RELAYFILE_FULL_PULL_READ_CONCURRENCY in the environment that initialised the package gate. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com> Session-Id: cfcb450a-cb3d-44b8-b164-ee16099b74f9
A SIGUSR1 flush that arrived while the daemon was still waiting out its startup splay (up to 5m) stayed queued until the splay ended, so `--notify-flush` gave up after notifyFlushWait (2x the cycle timeout) without an ack. A flush now ends the splay and is serviced immediately through the same handler as the main loop (serviceFlushRequest). The splay test pins its sample (startupSplaySample) instead of retrying a random draw, so it no longer depends on the cycle's outcome. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com> Session-Id: cfcb450a-cb3d-44b8-b164-ee16099b74f9
The public `relayfile mount` command runs its own loop (runMountLoopWithAuthLock), so only standalone relayfile-mount waited out the startup splay; simultaneous public mounts still bootstrapped in lockstep. Add --startup-jitter / RELAYFILE_MOUNT_STARTUP_JITTER (default 5s, max 5m) and wait before the first cycle. Each scoped runner calls the loop separately and draws its own delay; cancellation keeps the existing once-mode error and daemon-mode clean stop. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com> Session-Id: cfcb450a-cb3d-44b8-b164-ee16099b74f9
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Cursor Bugbot has reviewed your changes using default effort and found 1 potential issue.
❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.
Reviewed by Cursor Bugbot for commit 389705d. Configure here.
… mutex The GitHub tar seed acquired its full-pull slot before runFullPullIO released s.mu, so while sibling scopes owned every slot this Syncer's local writeback, outbox and watcher handling were blocked for the rest of their streams. Acquire inside runFullPullIO like every other gated read, and do not record a gate wait cancellation as a cloud failure (Bugbot). Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com> Session-Id: cfcb450a-cb3d-44b8-b164-ee16099b74f9
TestOptionsMatchSourceFlagSets requires every flag runMount registers to be declared in the command table; regenerate the SDK command-spec snapshot with gen-command-spec.mjs. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com> Session-Id: cfcb450a-cb3d-44b8-b164-ee16099b74f9
End-to-end evidence: real
|
| first-read spread across scopes | max full-pull reads in flight | |
|---|---|---|
red (origin/main) |
0.21s | 6 |
| green | 11.86s (drawn splays 3.1–15.0s) | 2 |
The export path makes one read per scope, so the win here comes from the startup splay.
B. One process running 6 in-process scoped syncers (runScopedPollingMounts), per-file bootstrap path
The proxy returns 404 for export and bulk-read, as older servers do, so the mount falls back to tree listing plus individual reads.
| first-read spread across scopes | max full-pull reads in flight (all scopes) | |
|---|---|---|
red (origin/main) |
0.00s | 24 (6 syncers × 4 workers) |
| green | 16.70s | 4 (the process-wide cap) |
Each run made 366 full-pull reads. Scoped layout is refused at the CLI surface, so scenario B calls the runner from a build-tagged test that is not committed.
Caveat on the process-wide cap
Cloud's packages/core/src/relayfile/mount-script.ts states that multi-path mounts run one process per remote root, and both CLIs currently refuse scoped layout. So in production today the cap bounds each process, not the whole workspace. Scenario A shows that the startup splay is what spreads concurrent processes' bootstraps.
Unit-level red → green (per review thread)
- Tar seed and gate:
TestGithubTarSeedHoldsFullPullSlotUntilBodyClosed: red on the unfixed code for both the manifest read and the body-held stream.TestGithubTarSeedWaitsForSlotWithoutHoldingSyncerMutex: red, "Syncer mutex was held…".TestConcurrentSyncerBootstrapsShareProcessWideReadBudget: the original version failed underRELAYFILE_FULL_PULL_READ_CONCURRENCY=16with "= 12, want <= 4".
- Flush during splay:
TestFlushRequestDuringStartupSplayIsAcknowledgedPromptlywas red ("not acknowledged within 4s"). - Public
relayfile mount:TestPublicMountLoopWaitsStartupSplayBeforeFirstRequestwas red.
2 participants
Summary
The mount client has no timers tied to the clock: the periodic loop is already ±20% jittered, and
integrationCatalogTTLis only a CLI cache TTL. It did make simultaneous starts worse in two ways:This complements AgentWorkforce/cloud fix/relaycron-schedule-splay (the root cause: every schedule fired at exactly HH:00).
Change
relayfile-mount: new--startup-jitterflag, also settable asRELAYFILE_MOUNT_STARTUP_JITTER.--once, which has not bootstrapped yet.mountsync: a process-widefullPullReadGatecaps in-flight full-pull reads at 4 across all Syncers.RELAYFILE_FULL_PULL_READ_CONCURRENCY, max 16.DeadlineExceededand takes the existing resumable-yield path.Tests
internal/mountsync/fullpull_gate_test.go:cmd/relayfile-mount/startup_splay_test.go:runSinglePollingMountmakes zero workspace requests during the splay. Mutation-checked: it fails when the wait is removed.go test ./... -count=1: all 14 packages pass.-race, the pre-existing timing assertionTestPullRemoteFullTreePrunesNestedMountRuntimeBeforeDescendantEnumeration(<500ms) failed once during the loaded full run. In 8 isolated race runs each it took about 0.3s with and without this change, so it's a timing flake, not a regression.🤖 Generated with Claude Code
Note
Medium Risk
Touches bootstrap timing and all full-pull I/O paths in mountsync; mis-tuning could slow initial sync or change concurrency under load, but defaults preserve single-scope throughput and behavior is env-flag tunable.
Overview
Adds startup splay and a process-wide full-pull read cap so many mounts bootstrapping together do not hammer the workspace Durable Object in the same second.
Startup jitter:
--startup-jitter/RELAYFILE_MOUNT_STARTUP_JITTER(default 5s, max 5m, 0 disables) onrelayfile mountandrelayfile-mount. Each scoped runner draws a uniform random delay before the first reconcile; cancellation during the wait fails--oncecleanly. Onrelayfile-mount, a SIGUSR1 flush during the splay skips the wait and runs reconcile immediately (serviceFlushRequest); the public CLI mount loop gets the same delay behavior.Read gate:
mountsyncaddsfullPullReadGate(default 4 concurrent reads per process, tunable viaRELAYFILE_FULL_PULL_READ_CONCURRENCY, max 16) across tree pages, bulk/point bootstrap reads, export snapshots, and GitHub tar seeding (slot held until the tar body closes). Gate waits respectcontextfor resumable yields; tar slot acquisition stays outside the Syncer mutex while waiting.CLI command spec and TypeScript
command-spec.jsondocument the new flag. Tests cover splay bounds, zero workspace traffic during splay, flush-during-splay acks, and multi-Syncer read concurrency.Reviewed by Cursor Bugbot for commit 76c8e2b. Bugbot is set up for automated code reviews on this repo. Configure here.