Lock all read/writes of selected keys via the public key set #147
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With our PoC at https://github.com/kevink-sq/jetty-concurrency-issue-poc/tree/575469b3453e7b09d9d60f6460cdab8117b8e773, we noticed that there is unbounded growth of file descriptors when running our simple load test: ```bash seq 1 15000 | xargs -P1500 -I{} curl --unix-socket ./junix-ingress.sock http://localhost/process ``` Leading to timeouts from curl and timeout exceptions in jetty: ``` java.util.concurrent.TimeoutException: Idle timeout expired: 32422/30000 ms at org.eclipse.jetty.io.IdleTimeout.checkIdleTimeout(IdleTimeout.java:170) at org.eclipse.jetty.io.IdleTimeout.idleCheck(IdleTimeout.java:112) at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:539) at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264) at java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:304) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635) at java.base/java.lang.Thread.run(Thread.java:833) ``` This patch fixes the issue by ensuring that keys with the `OP_INVALID` bit are still tracked in the selected key set and cancelled accordingly Changes: * Add invalid keys to `selectedKeysSet` in `setOpsReady` and mark as cancelled, ensuring that the fd is cleaned up timely * Switch from `cancelNoRemove` to `cancel` now that the registered keys are modified separately in the select implementation * Prefer `!key.isValid()` over `key.hasOpInvalid()` since the former is a superset of the latter * In `implCloseSelector`, cancel the keys before clearing `keysRegistered` since `keys()` is backed by `keysRegistered` * Store cancelled keys in a deque instead of a hash set, which should be a little more efficient * Remove dead code
This ensures that the selector and its clients use the same lock to synchronize access to the selected keys Changes: * Always lock on `selectedKeysPublic` to be consistent with clients * Synchronize on `selectedKeysPublic` when adding or clearing selected keys * Reorder the calls to `consumeAllBytesAfterPoll` and `selectedKeysPublic.clear()` after polling in order to push down the lock on `selectedKeysPublic`. This should be safe since neither the channel closing loop nor `consumeAllBytesAfterPoll` operates on the selected key set * Remove redudnant use of `synchronized` on methods that are always called under a lock on `this`. Use assertions to document what locks are required for the given method instead
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I guess with the latest changes, this is no longer being pursued? |
I don't think the new locking strategy is compatible with this PR, so I'll close this for now. |
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This ensures that the selector and its clients use the same lock to synchronize access to the selected keys
Changes:
selectedKeysPublicto be consistent with clientsselectedKeysPublicwhen adding or clearing selected keysconsumeAllBytesAfterPollandselectedKeysPublic.clear()after polling in order to push down the lock onselectedKeysPublic. This should be safe since neither the channel closing loop norconsumeAllBytesAfterPolloperates on the selected key setsynchronizedon methods that are always called under a lock onthis. Use assertions to document what locks are required for the given method instead