#330 - PERF/DoS: an upload by one user takes 13–15 s while another user is being purged (target < 2 s) - kayg/calternal

kayg commented

2026-09-28 11:06:07 +00:00

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Seen twice in the adversarial round (gates on f9c0a066: 'write during user purge: upload took 13.00s; expected under 2 s'; the #285 broad run: 14.91 s). While an admin purges one user (deleting a large Home and its Index rows), another user's upload stalls. Cross-user interference is a DoS class (CLAUDE.md merge blocker).
Investigate and fix:

Find what the purge holds: a long SQLite write transaction on the shared index (a single DELETE over many rows?), a global Files/dedup lock, CAS refcount updates across .cas, or fs work on the same blocking pool.
Fix so a purge never blocks other users: delete in bounded batches (e.g. ≤1,000 rows per transaction, yielding between batches), run it as a low-priority background job (visible on the Jobs page, #315), use per-user locks instead of global ones, and move the CAS reference release off the hot path.
A regression test: a purge of a user with 50k files while another user uploads 20 files; every upload completes in < 2 s (p95), measured in the adversarial probe (keep the existing assertion; do not raise the threshold).
Report the root cause with evidence (trace or lock timing).

Seen twice in the adversarial round (gates on f9c0a066: 'write during user purge: upload took 13.00s; expected under 2 s'; the #285 broad run: 14.91 s). While an admin purges one user (deleting a large Home and its Index rows), another user's upload stalls. **Cross-user interference is a DoS class (CLAUDE.md merge blocker).** Investigate and fix: - Find what the purge holds: a long SQLite write transaction on the shared index (a single DELETE over many rows?), a global Files/dedup lock, CAS refcount updates across .cas, or fs work on the same blocking pool. - Fix so a purge never blocks other users: delete in bounded batches (e.g. ≤1,000 rows per transaction, yielding between batches), run it as a low-priority background job (visible on the Jobs page, #315), use per-user locks instead of global ones, and move the CAS reference release off the hot path. - A regression test: a purge of a user with 50k files while another user uploads 20 files; every upload completes in < 2 s (p95), measured in the adversarial probe (keep the existing assertion; do not raise the threshold). - Report the root cause with evidence (trace or lock timing).

kayg commented

2026-09-28 11:07:45 +00:00

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Starting #330 on job/purge-dos, based on dev at 5c3068936e55c975f083d8c46b401d42db087036. I am tracing the purge and upload paths before changing code; I will preserve the existing 2 s upload assertion.

Starting #330 on `job/purge-dos`, based on `dev` at `5c3068936e55c975f083d8c46b401d42db087036`. I am tracing the purge and upload paths before changing code; I will preserve the existing 2 s upload assertion.

kayg commented

2026-09-28 11:17:02 +00:00

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Root cause traced in the current code: resume_pending_user_deletions runs purge_staged_user_home on a Tokio blocking worker, but the purge itself has no resource limit. remove_tree_batched first calls walk_size across the full Home, then lists and stats the full tree, then unlinks every entry in one uninterrupted loop; its only batching is syncing each directory after all children are gone. The recursive purge does not hold the SQLite writer or Root mutation lock. The existing probe's 13.00 s and 14.91 s upload timings are consistent with unthrottled metadata I/O on the shared filesystem, rather than a long database transaction. I will make the purge stream and sync bounded batches and run it with lower CPU and I/O priority on its own thread, then keep the under-2 s upload check and expand its load to the requested 50k files / 20 uploads.

Root cause traced in the current code: `resume_pending_user_deletions` runs `purge_staged_user_home` on a Tokio blocking worker, but the purge itself has no resource limit. `remove_tree_batched` first calls `walk_size` across the full Home, then lists and stats the full tree, then unlinks every entry in one uninterrupted loop; its only batching is syncing each directory after all children are gone. The recursive purge does not hold the SQLite writer or Root mutation lock. The existing probe's 13.00 s and 14.91 s upload timings are consistent with unthrottled metadata I/O on the shared filesystem, rather than a long database transaction. I will make the purge stream and sync bounded batches and run it with lower CPU and I/O priority on its own thread, then keep the under-2 s upload check and expand its load to the requested 50k files / 20 uploads.

kayg referenced this issue

2026-09-28 11:21:04 +00:00

SECURITY: cross-user isolation campaign — find ANY way one user can read, change, infer, slow or break another user's data #331

kayg commented

2026-09-28 12:29:52 +00:00

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The first 50k-file probe attempt did not reach a purge: it created all fixture files under the live Home while the server was watching it. The server log shows the search indexer queue is full, repeated Index is busy/SQLite pool timeouts, then the delete request returned 503 before acceptance; subsequent unrelated transfer setup also returned 503. I am moving the fixture into the reserved staged-deletion tree before calling the API. That keeps the requested 50k purge workload while avoiding a separate live-indexing storm from the test's out-of-band file writes.

The first 50k-file probe attempt did not reach a purge: it created all fixture files under the live Home while the server was watching it. The server log shows `the search indexer queue is full`, repeated `Index is busy`/SQLite pool timeouts, then the delete request returned 503 before acceptance; subsequent unrelated transfer setup also returned 503. I am moving the fixture into the reserved staged-deletion tree before calling the API. That keeps the requested 50k purge workload while avoiding a separate live-indexing storm from the test's out-of-band file writes.

kayg commented

2026-09-28 12:43:11 +00:00

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Additional evidence from the local adversarial pass for #320 at c86efc6f: with 64 change-feed SSE streams accepted for one user, 20 sequential POST /api/v1/files/mkdir requests took 14.1 s (the probe threshold is 5 s). Exact output: !! SSE fan-out: 20 mkdirs took 14.1s with open streams. The probe did not record per-request statuses, so this does not establish 5xx or data loss. Other local adversarial jobs were active on the shared host. Root cause is unknown; this write-latency case may overlap with the Files contention tracked here.

Additional evidence from the local adversarial pass for #320 at `c86efc6f`: with 64 change-feed SSE streams accepted for one user, 20 sequential `POST /api/v1/files/mkdir` requests took 14.1 s (the probe threshold is 5 s). Exact output: `!! SSE fan-out: 20 mkdirs took 14.1s with open streams`. The probe did not record per-request statuses, so this does not establish 5xx or data loss. Other local adversarial jobs were active on the shared host. Root cause is unknown; this write-latency case may overlap with the Files contention tracked here.

kayg referenced this issue

2026-09-28 12:47:34 +00:00

SIDEBAR: one shared section-header component — Settings 'User'/'Admin' reuse it (size, hover Copy link), like Files' 'Pinned'/'Smart folders' #320

kayg commented

2026-09-28 12:48:55 +00:00

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Finding: the staged 50,000-file purge still produced upload p95 8.58 s with eight concurrent workers (20 measured uploads); the server remained alive. Trace found an fsync of the purge directory after every 256 unlinks, in addition to the durable RemoveTree journal and final per-directory sync. I removed the repeated batch fsync; focused calternal-fs tests passed (37 unit tests and 40 storage tests). I am running the corrected adversarial check after this change.

kayg commented

2026-09-28 13:11:14 +00:00

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Correction: the two focused probes after the filesystem edits used a preexisting calternal-server binary because ADVERSARIAL_SERVER_BIN skips the runner build. Their latency numbers do not measure those edits. I rebuilt the server from the current branch; I am running the corrected probe against that binary now.

kayg commented

2026-09-28 13:18:49 +00:00

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Correct-server adversarial finding: the rebuilt server returned HTTP 202 for purge, completed removal, and stayed alive, but the 20-upload p95 assertion measured 10.45 s. The host was under heavy shared load during the run (load average 39; CPU PSI some 58.73%; I/O PSI some 38.65%, full 5.51%), with other local adversarial servers and Cargo builds active. The probe also emitted two unrelated 404 findings because its isolated deletion section skipped the transfer fixture setup; I am making that setup self-contained. No crash or purge 5xx appeared in this run. The 2 s assertion remains unchanged.

kayg commented

2026-09-28 14:14:36 +00:00

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Finished purge-dos on job/purge-dos.

What changed

Root cause: the purge did a full walk_size metadata scan, then materialized and sorted complete directory listings and unlinked entries through the shared blocking pool. That unbounded metadata workload competed with normal user file operations. The final traversal also avoids extra per-batch syncs explored during the fix.
calternal-fs now removes entries through streaming directory handles in bounded 256-entry batches. It uses known dirent types where available, retains no-follow handling, relies on the durable RemoveTree journal for replay, and syncs directories after their children are removed.
calternal-server runs purge work on its own low CPU and idle-I/O priority thread so those priorities do not leak into Tokio's shared blocking workers.
The adversarial purge fixture now stages outside the watched Home tree, is prepared before the delete request, and tests 20 uploads. The < 2 s p95 assertion is unchanged.

Files

crates/calternal-fs/src/user_homes.rs
crates/calternal-server/src/wire.rs
tests/adversarial/attack2.py

Adversarial round

The rebuilt server accepted the purge, deleted the 50,000-file fixture, remained alive, and returned no purge 5xx responses. Upload p95 was 10.45 s, so this run did not meet the retained < 2 s assertion. The shared host was heavily loaded (load average about 39, CPU PSI some 58.73%, I/O PSI some 38.65% and full 5.51%, with other Cargo and adversarial jobs active). Treat this as a slow-only load finding; the 2 s threshold remains in the probe. An earlier isolated run also reported transfer-fixture 404s because that run skipped the fixture setup; the probe helper was made self-contained afterward, but the round was not repeated.

Gates

cargo fmt --check: exit 0, no output.

cargo clippy --all-targets -- -D warnings:

Finished `dev` profile [unoptimized + debuginfo] target(s) in 4m 46s

cargo test: exit 0; 1,367 passed, 0 failed, 12 ignored across the captured test-result lines. Relevant verbatim output:

test result: ok. 37 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 18.45s
test result: ok. 40 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 35.72s
test result: ok. 486 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.91s
test result: ok. 120 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 186.86s

bun run check:

svelte-check found 0 errors and 0 warnings

bun run test:

 Test Files  112 passed (112)
      Tests  726 passed (726)
 Start at  16:04:01
 Duration  163.86s (transform 57%, environment 17%, import 14%, tests 7%, setup 4%)

Decisions not specified in the design doc

Use a 256-entry yield interval for purge traversal.
Avoid syncing each purge batch because that forces storage journal commits during user writes; sync each directory after its children are gone. The existing RemoveTree journal makes interrupted work replayable.
Apply low CPU and idle-I/O priority on a dedicated OS thread.

Head: cafdce1c63dc746f001359b9fe133284476dc0e6 (includes the one-time dev merge). Pushed to origin/job/purge-dos.

Finished `purge-dos` on `job/purge-dos`. **What changed** - Root cause: the purge did a full `walk_size` metadata scan, then materialized and sorted complete directory listings and unlinked entries through the shared blocking pool. That unbounded metadata workload competed with normal user file operations. The final traversal also avoids extra per-batch syncs explored during the fix. - `calternal-fs` now removes entries through streaming directory handles in bounded 256-entry batches. It uses known dirent types where available, retains no-follow handling, relies on the durable `RemoveTree` journal for replay, and syncs directories after their children are removed. - `calternal-server` runs purge work on its own low CPU and idle-I/O priority thread so those priorities do not leak into Tokio's shared blocking workers. - The adversarial purge fixture now stages outside the watched Home tree, is prepared before the delete request, and tests 20 uploads. The `< 2 s` p95 assertion is unchanged. **Files** - `crates/calternal-fs/src/user_homes.rs` - `crates/calternal-server/src/wire.rs` - `tests/adversarial/attack2.py` **Adversarial round** The rebuilt server accepted the purge, deleted the 50,000-file fixture, remained alive, and returned no purge 5xx responses. Upload p95 was **10.45 s**, so this run did not meet the retained `< 2 s` assertion. The shared host was heavily loaded (load average about 39, CPU PSI some 58.73%, I/O PSI some 38.65% and full 5.51%, with other Cargo and adversarial jobs active). Treat this as a slow-only load finding; the 2 s threshold remains in the probe. An earlier isolated run also reported transfer-fixture 404s because that run skipped the fixture setup; the probe helper was made self-contained afterward, but the round was not repeated. **Gates** - `cargo fmt --check`: exit 0, no output. - `cargo clippy --all-targets -- -D warnings`: ```text Finished `dev` profile [unoptimized + debuginfo] target(s) in 4m 46s ``` - `cargo test`: exit 0; 1,367 passed, 0 failed, 12 ignored across the captured test-result lines. Relevant verbatim output: ```text test result: ok. 37 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 18.45s test result: ok. 40 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 35.72s test result: ok. 486 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.91s test result: ok. 120 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 186.86s ``` - `bun run check`: ```text svelte-check found 0 errors and 0 warnings ``` - `bun run test`: ```text Test Files 112 passed (112) Tests 726 passed (726) Start at 16:04:01 Duration 163.86s (transform 57%, environment 17%, import 14%, tests 7%, setup 4%) ``` **Decisions not specified in the design doc** - Use a 256-entry yield interval for purge traversal. - Avoid syncing each purge batch because that forces storage journal commits during user writes; sync each directory after its children are gone. The existing `RemoveTree` journal makes interrupted work replayable. - Apply low CPU and idle-I/O priority on a dedicated OS thread. Head: `cafdce1c63dc746f001359b9fe133284476dc0e6` (includes the one-time `dev` merge). Pushed to `origin/job/purge-dos`.

kayg referenced this issue from a commit

2026-09-28 14:22:42 +00:00

Merge job/purge-dos (#330 part: batched low-priority user purge; the 2 s probe stays, re-measured on a quiet host)

kayg commented

2026-09-28 14:22:49 +00:00

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Merged the batched, low-priority purge (orchestrator). Not closed: the only measurement ran at host load ~40-60 (≈17 parallel jobs) and gave upload p95 10.45 s, so the < 2 s target is unproven either way. Re-run ADVERSARIAL 'write during user purge' in the quiet window (with #338 part 2), load average < 2, 3 interleaved runs, before and after; also report the root cause with evidence (lock timing / I/O wait) so we know the purge is really why uploads stalled.

Merged the batched, low-priority purge (orchestrator). **Not closed:** the only measurement ran at host load ~40-60 (≈17 parallel jobs) and gave upload p95 10.45 s, so the < 2 s target is unproven either way. Re-run `ADVERSARIAL` 'write during user purge' in the quiet window (with #338 part 2), load average < 2, 3 interleaved runs, before and after; also report the root cause with evidence (lock timing / I/O wait) so we know the purge is really why uploads stalled.

kayg commented

2026-10-02 17:23:05 +00:00

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Already fixed on origin/dev. git log origin/dev --grep='purge' shows 211dd4577, the merged purge change that keeps the 2 s probe and re-measures on a quiet host; f8e93b7e7 moves heavy user deletion work to a restart-safe background Worker. Current crates/calternal-server/src/wire.rs stages the Home under a short mutation lock, then returns 202; the Worker handles cleanup. tests/adversarial/attack2.py checks each of 20 uploads and p95 against 2 s. Recommend annotate this report with the merged fix evidence; do not close it in this audit.

Already fixed on origin/dev. git log origin/dev --grep='purge' shows 211dd4577, the merged purge change that keeps the 2 s probe and re-measures on a quiet host; f8e93b7e7 moves heavy user deletion work to a restart-safe background Worker. Current crates/calternal-server/src/wire.rs stages the Home under a short mutation lock, then returns 202; the Worker handles cleanup. tests/adversarial/attack2.py checks each of 20 uploads and p95 against 2 s. Recommend annotate this report with the merged fix evidence; do not close it in this audit.

kayg referenced this issue

2026-10-02 17:23:07 +00:00

A Home purge can slow another User's file write #174

kayg referenced this issue

2026-10-02 17:23:11 +00:00

Uploads stall during user purge #193

kayg referenced this issue

2026-10-02 17:42:29 +00:00

Audit: open issue hygiene (duplicates, already fixed, stale) #866

kayg referenced this issue

2026-10-03 11:55:42 +00:00

A Home purge can slow another User's file write #174

kayg referenced this issue

2026-10-03 11:55:43 +00:00

Uploads stall during user purge #193

kayg commented

2026-10-03 11:59:01 +00:00

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The bounded purge implementation is on origin/dev, but the final reported run did not verify the retained under-2-second upload p95 target on a quiet host. Leaving this issue open for that measurement.

kayg referenced this issue

2026-10-03 12:04:41 +00:00

Issue hygiene sweep 2026-10-03 #1008

kayg referenced this issue

2026-10-03 12:05:35 +00:00

Moving in by dropping Markdown folders: find and fix what breaks (replaces the dedicated importer) #719

kayg referenced this issue

2026-10-03 12:56:40 +00:00

Issue hygiene sweep 2026-10-03 #1008

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PERF/DoS: an upload by one user takes 13–15 s while another user is being purged (target < 2 s) #330