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| Layer / File(s) | Summary |
|---|---|
Retention settings and watcher identity packages/workspace-fs/src/watch.ts |
Watcher state records root identity and idle timers. Manager options set the keep-alive period and maximum idle watcher count. |
Idle watcher reuse and disposal packages/workspace-fs/src/watch.ts, packages/workspace-fs/src/watch-idle-keep-alive.test.ts, packages/workspace-fs/src/watch-overflow-backoff.test.ts |
The manager retains watchers after the final unsubscribe, reuses them when the root identity still matches, and disposes them on expiry, capacity eviction, or shutdown. Tests cover reuse, expiry, eviction, teardown races, changed roots, and repeated unsubscribe calls. |
Estimated code review effort: 3 (Moderate) | ~20 minutes
Change: Bug fix
Sequence Diagram(s)
sequenceDiagram
participant Subscriber
participant FsWatcherManager
participant Filesystem
participant NativeWatcher
Subscriber->>FsWatcherManager: Unsubscribe final listener
FsWatcherManager->>NativeWatcher: Retain attached subscription during idle period
Subscriber->>FsWatcherManager: Subscribe to watched root
FsWatcherManager->>Filesystem: Read root identity
Filesystem-->>FsWatcherManager: Return device, inode, and birth time
FsWatcherManager->>NativeWatcher: Reuse subscription if identity matches
Suggested reviewers: kitenite
Merge Risk: 
bb41d
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Workspace switches may unnecessarily rebuild watches, and concurrent subscriptions around a root replacement can miss filesystem events. Resolve the stale-reuse race and establish a safe root-identity strategy before merging.
Security Architecture Review
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Security architecture risk: 🟡 Moderate · up to
bb41dA retained watcher may continue watching an old directory if a workspace path is a symlink that changes destination while the watcher is idle. On reuse, events from that old directory could appear to come from the current workspace path. The usual lifetime and capacity limits constrain the exposure, but the path-identity check does not address this case.
Retained concerns
- Medium · security · inferred: Reusing an idle watcher can attach a new listener to the old target of a retargeted symlink and report that target's events under the requested workspace path.
Security review details
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Security Blast Radius
- inferred — The conditional stale-target exposure is confined to a previously watched root that remains available during the idle window; the evidence does not establish a cross-tenant path or elevated filesystem access.
Security Findings and Attack Paths
- inferred — If an actor able to retarget a watched symlink switches it from A to B while idle and A remains intact, a subsequent listener can receive events from A labeled with the requested path. Whether that reaches an unauthorized listener depends on caller ownership and permissions not established here.
Trust Boundaries and Controls
- observed — The inspected host-service watch route resolves a workspace root from its workspace identifier, and targeted file watches reject paths outside the worktree before reaching filesystem watching. These caller checks do not establish that a cached resolved target still matches a later symlink destination.
Resilience and Maintainability Implications
- observed — Root-identity mismatch, expiry, eviction, and manager shutdown provide disposal paths. The identity comparison protects against replacement of the resolved root itself, but does not resolve the caller's path again.
Hardening Proposals
- proposed — Before reusing an idle subscription, resolve the requested path again and require it to identify the attached root; otherwise discard and reattach. Exercise symlink retargeting separately from root deletion in lifecycle tests.
🚥 Pre-merge checks | ✅ 4 | ❌ 1
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❌ Failed checks (1 warning)
Check name Status Explanation Resolution Docstring Coverage ⚠️ WarningDocstring coverage is 14.29% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 7 functions across 3 files. Write docstrings for the functions missing them to satisfy the coverage threshold. ✅ Passed checks (4 passed)
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Check name Status Explanation Title check ✅ Passed The title uses conventional commit format and clearly describes the main change: keeping idle workspace watchers warm across workspace switches. Description check ✅ Passed The description is complete and relevant. It explains the problem, implementation, testing, performance results, and checklist status. The maintainer-edit permission remains unchecked, but the author … Linked Issues check ✅ Passed Check skipped because no linked issues were found for this pull request. Out of Scope Changes check ✅ Passed Check skipped because no linked issues were found for this pull request.
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Finishing Touches
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Actionable comments posted: 2
- 🪄 Fix CodeRabbit comments on this PR
🤖 Prompt to fix review comments
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Inline comments:
In `@packages/workspace-fs/src/watch.ts`:
- Around line 233-236: Update readRootIdentity to call stat with bigint enabled
and build the identity from only dev and ino, removing birthtimeMs so metadata
changes do not invalidate a healthy watcher.
- Around line 373-380: Serialize idle-state validation in the subscribe flow
around this.watchers and isStillAttached so concurrent calls share one pending
validation and cannot attach to a stale WatcherState. Keep the listener-count
guard before releaseWatcher so validation cannot dispose a state that has gained
listeners.
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ℹ️ Review info
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Configuration used: defaults
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Plan: Advanced
Run ID: f7d219c7-55a5-4f27-aa0a-c2f6aa0e8f3c
📒 Files selected for processing (3)
packages/workspace-fs/src/watch-idle-keep-alive.test.tspackages/workspace-fs/src/watch-overflow-backoff.test.tspackages/workspace-fs/src/watch.ts
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Merges upstream main into the watcher build. The watcher fixes are the current heads of ParadevAI#7878 and ParadevAI#7879 plus the two held-back ignored-dir listing fixes, unchanged from 1.37.1-fswatch.1. Requires the bundled pdev like upstream's Linux build does. Claude-Session: https://claude.ai/code/session_01DdpvAat4Xg6xSnojshGJAQ
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Switching workspaces sends fs:unwatch for the one being left (the useWorkspaceEvent effect depends on workspaceId), which drops the root watcher's last listener, and FsWatcherManager disposed it on the spot. Switching back re-attached from scratch: on a large monorepo on Linux that is ~23k inotify watches rebuilt over 5-7 s at 150-640% CPU, on every switch. A watcher whose last listener leaves now stays attached for 60 s, and a re-subscribe in that window reuses it. At most 3 idle watchers are kept; beyond that the longest-idle one is disposed, so idle cost stays bounded as worktree count grows. Expiry, eviction and close() dispose exactly as before; idleKeepAliveMs: 0 restores immediate disposal. A watcher is never handed back on a dead tree: a suspended one (root deleted) is released instead of parked, and before reuse the root's dev/ino/birthtime is compared with the one recorded at attach, since a root deleted and recreated while idle is not always reported in time. Claude-Session: https://claude.ai/code/session_01CZBCrRCZ2rEBHv4DH3Wh3k
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I have read the CLA Document and I hereby sign the CLA You can retrigger this bot by commenting recheck in this Pull Request. Posted by the CLA Assistant Lite bot. |
HEAD: patiently:pr/fs-watcher-keep-alive → BASE: superset-sh:main
What & why
Refs #7877 (cause 1).
FsWatcherManager.subscribe()disposed a root's watcher as soon as its last listener left, so every workspace switch threw away the old workspace's watcher, and switching back crawled the whole tree again. On a monorepo that's ~23k inotify watches rebuilt per switch at 150–400% host-service CPU, and under steady switching the crawls stack into bursts of up to 377k.A watcher whose last listener leaves now stays attached for 60 s, and a re-subscribe in that window reuses it. At most 3 idle watchers are kept, and beyond that the longest-idle one is disposed, so the idle cost stays bounded as the worktree count grows. Expiry, eviction and
close()dispose exactly as before, andidleKeepAliveMs: 0restores immediate disposal.It builds on #7865's attach model rather than around it. Shared pending attaches, cancellation and the catch-up event are unchanged, and releasing a watch whose attach is still in flight still cancels it; only a fully attached watcher goes idle. A watcher is never handed back on a dead tree: a suspended one (root deleted) is released instead of parked, and before reuse the root's dev/ino/birthtime is compared with the one recorded at attach, because a root deleted and recreated while idle isn't always reported.
How I tested it
watch-idle-keep-alive.test.ts(fake backend) covers:close()disposing idle watchersidleKeepAliveMs: 0main2370f60 plus this PR, the hover PR and two small ignored-dir listing changes.main2370f60, same machine, scripted 30-minute workload (method in [perf] Linux: every workspace switch and sidebar hover re-crawls the whole worktree (bursts to 377k inotify watches) #7877). That fixed arm also included the hover PR and the two listing changes, which had no observable effect in that run:The median is higher by design (up to 3 warm workspaces); the bursts are gone. Nothing is user-visible, so there are no screenshots.
Checklist
type(scope): subject)bun run lintandbun run typecheckpass (fork CI run above)Summary by cubic
Keeps watchers warm across workspace switches so switching back no longer re-crawls the whole tree. Previously dropping a root's last listener disposed its watcher immediately, so every switch rebuilt ~23k inotify watches at heavy host-service CPU; a watcher now stays attached for 60 s and is reused if re-subscribed in that window.
At most 3 idle watchers are kept, with the longest-idle evicted first, so idle cost stays bounded as worktree count grows. Expiry, eviction, and
close()dispose as before, andidleKeepAliveMs: 0ormaxIdleWatchers: 0restores immediate disposal. An idle watcher is never reused on a dead tree: suspended watchers are released instead of parked, and the root's dev/ino/birthtime is verified before reuse because a recreated root isn't always reported while idle.Written for commit ee320ea. Summary will update on new commits.
Summary by CodeRabbit