Deadlock when numerous identical actions run at the same time

[chrisstaite-menlo]

On a rare occasion it appears that workers somehow end up processing all of the requests twice and therefore end up locking themselves up. This is the cause for the random worker lock up, but I'm not sure why it happens.

Here's an example log:

warn{"timestamp":"2025-10-22T09:47:21.604176Z","level":"WARN","fields":{"message":"Running prepare_action for DigestInfo(\"f6bf3a8df3a1b6bc5d7fe27ae5419ace6900fc3cc414226c29b9e0eb03bc645b-5264\")"},"target":"nativelink_worker::running_actions_manager","span":{"name":"worker_start_action"},"spans":[{"name":"\"worker_0\"","name":"worker"},{"name":"worker_start_action"}]}

warn{"timestamp":"2025-10-22T09:47:21.604176Z","level":"WARN","fields":{"message":"Running prepare_action for DigestInfo(\"f6bf3a8df3a1b6bc5d7fe27ae5419ace6900fc3cc414226c29b9e0eb03bc645b-5264\")"},"target":"nativelink_worker::running_actions_manager","span":{"name":"worker_start_action"},"spans":[{"name":"\"worker_0\"","name":"worker"},{"name":"worker_start_action"}]}

warn{"timestamp":"2025-10-22T09:47:21.614965Z","level":"WARN","fields":{"message":"Running prepare_action for DigestInfo(\"e928292e301bc3ac4d92adb91ed6c4c0f970dbd1f25e8770dd5bd169f640b75f-13180\")"},"target":"nativelink_worker::running_actions_manager","span":{"name":"worker_start_action"},"spans":[{"name":"\"worker_0\"","name":"worker"},{"name":"worker_start_action"}]}

warn{"timestamp":"2025-10-22T09:47:21.614965Z","level":"WARN","fields":{"message":"Running prepare_action for DigestInfo(\"e928292e301bc3ac4d92adb91ed6c4c0f970dbd1f25e8770dd5bd169f640b75f-13180\")"},"target":"nativelink_worker::running_actions_manager","span":{"name":"worker_start_action"},"spans":[{"name":"\"worker_0\"","name":"worker"},{"name":"worker_start_action"}]}

warn{"timestamp":"2025-10-22T09:47:21.636644Z","level":"WARN","fields":{"message":"Running prepare_action for DigestInfo(\"4111923225b3a30fda94fdc797ace9d6561bcfb4fe8afac60e8bc4b41eea9173-13249\")"},"target":"nativelink_worker::running_actions_manager","span":{"name":"worker_start_action"},"spans":[{"name":"\"worker_0\"","name":"worker"},{"name":"worker_start_action"}]}

warn{"timestamp":"2025-10-22T09:47:21.636644Z","level":"WARN","fields":{"message":"Running prepare_action for DigestInfo(\"4111923225b3a30fda94fdc797ace9d6561bcfb4fe8afac60e8bc4b41eea9173-13249\")"},"target":"nativelink_worker::running_actions_manager","span":{"name":"worker_start_action"},"spans":[{"name":"\"worker_0\"","name":"worker"},{"name":"worker_start_action"}]}

warn{"timestamp":"2025-10-22T09:47:21.639999Z","level":"WARN","fields":{"message":"Running prepare_action for DigestInfo(\"a70c0ab328b077af31640a2f880b9da5ee39730626eae7869bc791271a961943-5887\")"},"target":"nativelink_worker::running_actions_manager","span":{"name":"worker_start_action"},"spans":[{"name":"\"worker_0\"","name":"worker"},{"name":"worker_start_action"}]}

warn{"timestamp":"2025-10-22T09:47:21.639999Z","level":"WARN","fields":{"message":"Running prepare_action for DigestInfo(\"a70c0ab328b077af31640a2f880b9da5ee39730626eae7869bc791271a961943-5887\")"},"target":"nativelink_worker::running_actions_manager","span":{"name":"worker_start_action"},"spans":[{"name":"\"worker_0\"","name":"worker"},{"name":"worker_start_action"}]}

warn{"timestamp":"2025-10-22T09:47:21.677947Z","level":"WARN","fields":{"message":"Running prepare_action for DigestInfo(\"26d6ae6eb8c14431e2e931d35b1ab90f8c369452885c002f4c654770ff2b4742-13242\")"},"target":"nativelink_worker::running_actions_manager","span":{"name":"worker_start_action"},"spans":[{"name":"\"worker_0\"","name":"worker"},{"name":"worker_start_action"}]}

warn{"timestamp":"2025-10-22T09:47:21.677947Z","level":"WARN","fields":{"message":"Running prepare_action for DigestInfo(\"26d6ae6eb8c14431e2e931d35b1ab90f8c369452885c002f4c654770ff2b4742-13242\")"},"target":"nativelink_worker::running_actions_manager","span":{"name":"worker_start_action"},"spans":[{"name":"\"worker_0\"","name":"worker"},{"name":"worker_start_action"}]}

warn{"timestamp":"2025-10-22T09:47:21.678043Z","level":"WARN","fields":{"message":"Running prepare_action for DigestInfo(\"96f50fb4fba62a463cf13c9586e2c1b953af94263744a8094850ba8569b3752c-5754\")"},"target":"nativelink_worker::running_actions_manager","span":{"name":"worker_start_action"},"spans":[{"name":"\"worker_0\"","name":"worker"},{"name":"worker_start_action"}]}

warn{"timestamp":"2025-10-22T09:47:21.678043Z","level":"WARN","fields":{"message":"Running prepare_action for DigestInfo(\"96f50fb4fba62a463cf13c9586e2c1b953af94263744a8094850ba8569b3752c-5754\")"},"target":"nativelink_worker::running_actions_manager","span":{"name":"worker_start_action"},"spans":[{"name":"\"worker_0\"","name":"worker"},{"name":"worker_start_action"}]}

warn{"timestamp":"2025-10-22T09:47:21.678292Z","level":"WARN","fields":{"message":"Running prepare_action for DigestInfo(\"6a6b7c3a06506bcdc570529758eee869e5f9d5dc6ac0c77ff584019d88af9d7d-5789\")"},"target":"nativelink_worker::running_actions_manager","span":{"name":"worker_start_action"},"spans":[{"name":"\"worker_0\"","name":"worker"},{"name":"worker_start_action"}]}

warn{"timestamp":"2025-10-22T09:47:21.678292Z","level":"WARN","fields":{"message":"Running prepare_action for DigestInfo(\"6a6b7c3a06506bcdc570529758eee869e5f9d5dc6ac0c77ff584019d88af9d7d-5789\")"},"target":"nativelink_worker::running_actions_manager","span":{"name":"worker_start_action"},"spans":[{"name":"\"worker_0\"","name":"worker"},{"name":"worker_start_action"}]}

warn{"timestamp":"2025-10-22T09:47:21.895726Z","level":"WARN","fields":{"message":"Running prepare_action for DigestInfo(\"bc9c9905197ec6852f8fde799daaf413aab7fba337861924a23f9aa4aa2d70c8-6052\")"},"target":"nativelink_worker::running_actions_manager","span":{"name":"worker_start_action"},"spans":[{"name":"\"worker_0\"","name":"worker"},{"name":"worker_start_action"}]}

warn{"timestamp":"2025-10-22T09:47:21.895726Z","level":"WARN","fields":{"message":"Running prepare_action for DigestInfo(\"bc9c9905197ec6852f8fde799daaf413aab7fba337861924a23f9aa4aa2d70c8-6052\")"},"target":"nativelink_worker::running_actions_manager","span":{"name":"worker_start_action"},"spans":[{"name":"\"worker_0\"","name":"worker"},{"name":"worker_start_action"}]}

This log came from a worker with this added to the start of inner_prepare_action:

tracing::warn!("Running prepare_action for {:?}", self.action_info.command_digest);

Having looked at the command digests, there's nothing special about them. So it would appear that somehow the worker has managed to register twice with the scheduler or something?

[chrisstaite-menlo]

I wonder if perhaps Tonic is managing to duplicate messages on the stream somehow? Maybe we need a sequence number and discard duplicate messages?

[chrisstaite-menlo]

Added code to check for duplicate operation IDs and it didn't trigger. Therefore I can only assume there's cloned operation IDs with identical command digests.