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Pageserver lifecycle : replace task_mgr spawn & shutdown with handle-based abstraction #4175

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problame opened this issue May 8, 2023 · 0 comments
Open

Pageserver lifecycle : replace task_mgr spawn & shutdown with handle-based abstraction #4175

problame opened this issue May 8, 2023 · 0 comments
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c/storage/pageserver Component: storage: pageserver

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@problame
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problame commented May 8, 2023

Motivation

DoD

  • task_mgr::shutdown_tasks, task_mgr::associate_with and task_mgr::is_shutdown_requested are gone
  • task_mgr::spawn callers get back a handle on the task they spawned
  • the task handle allows requesting task shutdown & waiting for task to exit
  • there are mechanisms to ensure that all tasks associated with a tenant have shut down
    • e.g., ability to assert at end of detach that all tasks associated with the tenant have stopped
      • this is critical for relocation correctness, task_mgr does a 90%-good job at it

bonus points / follow-up:

  • there is a mechanism to prevent new tasks from being started for a tenant (tombstone)
    • detach arms this mechanism
    • attach disables it
@shanyp shanyp added t/Epic Issue type: Epic c/storage/pageserver Component: storage: pageserver and removed t/Epic Issue type: Epic labels May 8, 2023
@shanyp shanyp changed the title Epic: replace task_mgr spawn & shutdown with handle-based abstraction Pageserver lifecycle : replace task_mgr spawn & shutdown with handle-based abstraction May 10, 2023
@problame problame mentioned this issue Mar 8, 2024
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koivunej added a commit that referenced this issue Mar 9, 2024
@koivunej
fix: on-demand downloads can outlive timeline shutdown (#7051)
b09d686 
## Problem

Before this PR, it was possible that on-demand downloads were started
after `Timeline::shutdown()`.

For example, we have observed a walreceiver-connection-handler-initiated
on-demand download that was started after `Timeline::shutdown()`s final
`task_mgr::shutdown_tasks()` call.

The underlying issue is that `task_mgr::shutdown_tasks()` isn't sticky,
i.e., new tasks can be spawned during or after
`task_mgr::shutdown_tasks()`.

Cc: #4175 in lieu of a more
specific issue for task_mgr. We already decided we want to get rid of it
anyways.

Original investigation:
https://neondb.slack.com/archives/C033RQ5SPDH/p1709824952465949

## Changes

- enter gate while downloading
- use timeline cancellation token for cancelling download

thereby, fixes #7054

Entering the gate might also remove recent "kept the gate from closing"
in staging.
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@problame @shanyp