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[Server] Add an opt-in per-session lock - #582
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chr-hertel wants to merge 4 commits into
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chr-hertel wants to merge 4 commits into
chr-hertel wants to merge 4 commits into
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Concurrent requests of one session no longer overwrite each other's changes to different keys.
Concurrent requests of one session take turns instead of losing each other's changes to the same key.
chr-hertel
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🟡 Changes recommended
Concurrent saves, resumed fibers, session destruction, and lease expiry still leave serialization gaps.
4 open findings
What changed in this PR
Adds concurrency protections for session-backed protocol state through incremental saves and an opt-in per-session lock.
Changes:
- Merges changed session keys onto freshly loaded data.
- Adds configurable Symfony-based session locking.
- Adds concurrency tests and usage documentation.
| File | Description |
|---|---|
CHANGELOG.md |
Records concurrency improvements. |
composer.json |
Suggests and tests with symfony/lock. |
docs/run/sessions.md |
Documents concurrent requests and lock setup. |
src/Server/Builder.php |
Exposes session-lock configuration. |
src/Server/Protocol.php |
Applies locking around protocol session operations. |
src/Server/Session/Session.php |
Tracks and merges changed keys. |
src/Server/Session/SessionLockInterface.php |
Defines the locking contract. |
src/Server/Session/SymfonySessionLock.php |
Implements Symfony-backed locking. |
tests/Unit/Server/ProtocolSessionLockTest.php |
Tests protocol locking behavior. |
tests/Unit/Server/Session/Fixture/FiberSessionLock.php |
Simulates locking between fibers. |
tests/Unit/Server/Session/SessionTest.php |
Tests changed-key merge semantics. |
tests/Unit/Server/Session/SymfonySessionLockTest.php |
Tests lock acquisition and release. |
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| 'session_id' => $sessionId->toRfc4122(), | ||
| ]); | ||
| // Taken under the lock, from a fresh read, before the transport resumes the fiber with it. | ||
| $responseData = $this->locked($sessionId, fn (): mixed => $this->consumeResponse($requestId, $sessionId)); |
Comment on lines
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| if (null !== $this->changes) { | ||
| $data = $this->load(); | ||
| foreach (array_keys($this->changes) as $key) { | ||
| $this->apply($data, (string) $key); | ||
| } |
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Closed in favor of #584 |
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Stacked on #572 - that one keeps disjoint keys, but read-modify-write on the same key (a counter in a tool handler,
_mcp.pending_requests,_mcp.outgoing_queue) still loses updates under parallel requests. Follows the lock idea from #275.Builder::setSessionLock()with a smallSessionLockInterface, off by defaultSymfonySessionLockon top ofsymfony/lock(optional dependency), bounded wait =>TimeoutExceptionProtocolholds the lock from loading to saving the session; a suspended request saves and returns, so the lock is free while it waits on the client - the polling loop locks again only to take a response or queued messagesFixes chr-hertel#58 (together with #572)
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