apollo_storage: Use watch channels for marker tracking by dean-starkware · Pull Request #12690 · starkware-libs/sequencer

dean-starkware · 2026-02-18T10:29:32Z

Replace spawn_blocking-based marker reads with tokio::sync::watch channels. This eliminates the MDBX Thread Local Storage issue where uncommitted writes from one thread were not visible to reads from another thread in the blocking pool.

Note

Medium Risk
Changes core sync concurrency/marker propagation and compiled-class download flow; mistakes could stall progress or skip required compiled classes under certain config/compatibility conditions.

Overview
Sync now tracks header/state markers via tokio::sync::watch channels, updating them after each successful write, so block/state streams no longer poll storage each loop (avoids cross-thread MDBX visibility issues with batched/uncommitted writes).

Compiled class syncing is reworked from range-based stream_compiled_classes scanning markers to an event-driven model: after storing a state diff, the sync enqueues per-class CompiledClassRequests and fetches each CASM via get_compiled_class, while switching several validation/lookup reads to use the writer’s RW transaction for consistency. Tests are updated to mock get_compiled_class calls, and storage batching commit logic is slightly adjusted (removes a stray blank line only).

^{Written by Cursor Bugbot for commit fc546ad. This will update automatically on new commits. Configure here.}

reviewable-StarkWare · 2026-02-18T10:29:40Z

This change is

crates/apollo_central_sync/src/lib.rs

matanl-starkware

@matanl-starkware reviewed 2 files and all commit messages, and made 2 comments.
Reviewable status: all files reviewed, 2 unresolved discussions (waiting on dean-starkware).

crates/apollo_central_sync/src/lib.rs line 941 at r1 (raw file):

            // Skip forward through blocks without declared classes.
            while from < state_marker {
                let txn = reader.begin_ro_txn()?;

Here you don't have pending writes...

Code quote:

reader.begin_ro_txn()

crates/apollo_central_sync/src/lib.rs

crates/apollo_storage/src/state/mod.rs

crates/apollo_storage/src/lib.rs

crates/apollo_central_sync/src/lib.rs

github-actions · 2026-02-19T14:04:07Z

Artifacts upload workflows:

dean-starkware

@dean-starkware made 1 comment.
Reviewable status: 0 of 14 files reviewed, 1 unresolved discussion (waiting on matanl-starkware).

crates/apollo_central_sync/src/lib.rs line 941 at r1 (raw file):

Previously, matanl-starkware (Matan Lior) wrote…

Here you don't have pending writes...

Already fixed.

crates/apollo_central_sync/src/lib.rs

cursor

Cursor Bugbot has reviewed your changes and found 1 potential issue.

crates/apollo_central_sync/src/lib.rs

…ility bugs Replace direct DB marker reads in stream generators with tokio::sync::watch channels, eliminating spawn_blocking and MDBX thread-affinity issues. Remove spawn_blocking from perform_storage_writes to prevent MDBX TLS violations that caused State marker mismatches when batching was enabled. Switch compiler_backward_compatibility_marker and compiled_class_marker reads from begin_ro_txn to begin_rw_txn so they see uncommitted batched writes, fixing Class marker mismatches. Co-authored-by: Cursor <cursoragent@cursor.com>

cursor bot reviewed Feb 18, 2026

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crates/apollo_central_sync/src/lib.rs Outdated Show resolved Hide resolved

dean-starkware assigned matanl-starkware Feb 18, 2026

matanl-starkware requested changes Feb 18, 2026

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crates/apollo_central_sync/src/lib.rs Outdated Show resolved Hide resolved

dean-starkware force-pushed the dean/storage-batching-channel-markers branch 2 times, most recently from 1081b9f to d1ec325 Compare February 19, 2026 11:12