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Posted to github@arrow.apache.org by "thinkharderdev (via GitHub)" <gi...@apache.org> on 2023/02/04 21:24:52 UTC
[GitHub] [arrow-ballista] thinkharderdev opened a new issue, #655: Issues with lost executor handling
thinkharderdev opened a new issue, #655:
URL: https://github.com/apache/arrow-ballista/issues/655
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While working on the cluster state refactor and observing some issues with handling of lost executors in our system, I think there are a couple of issues with the current approach:
1. In multi-scheduler deployments, an executor will register itself and send heartbeats with a particular scheduler.
2. Any scheduler can scheduler tasks on the executor
3. However, in the case of a `SIGTERM` the executor will call `executor_stopped` on the scheduler from 1.
This doesn't work particularly well with the curated task architecture since the scheduler from step 1 may not be the owner of the jobs which the executor is running when it gets the `SIGTERM`. At best this may cause the lost executor handling to not work correctly (or be delayed since the owning scheduler has to wait for a timeout). At worst it could corrupt the job state and cause unpredictable errors in the scheduler.
More broadly, resetting tasks immediately when an executor gets a `SIGTERM` is a bit limiting. The executor may have anywhere from 30s - 2 minutes (or maybe more) to cleanup and finish any existing work after receiving a `SIGTERM` and ideally we could take advantage of that to minimize disruptions.
**Describe the solution you'd like**
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We have an existing mechanism to broadcast executor state to all schedulers using the executor heartbeat. These will also go to a particular scheduler but can be broadcast fairly easily through `ClusterState`. So I would propose the following:
1. Remove the `executor_stopped` rpc.
2. Instead of sending the `executor_stopped` rpc on `SIGTERM` the executor can just send a heartbeat where it's state changes from `Active` to `Dead` (or maybe something more descriptive like `ShuttingDown`).
3. When receiving that heartbeat the scheduler can put that executor in a "quarantine" state which means:
a. Stop scheduling new tasks on it
b. Wait for some (configurable) interval before resetting tasks
This can ensure that we handle job updates on the appropriate scheduler and that we can attempt to finish outstanding work before potentially re-computing tasks/stages.
**Describe alternatives you've considered**
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The executor could maybe track all schedulers for which it has active tasks and send an `executor_stopped` rpc to all of them but the rpc itself seems somewhat duplicative of the existing heartbeat mechanism
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[GitHub] [arrow-ballista] mingmwang commented on issue #655: Issues with lost executor handling
Posted by "mingmwang (via GitHub)" <gi...@apache.org>.
mingmwang commented on issue #655:
URL: https://github.com/apache/arrow-ballista/issues/655#issuecomment-1422102875
@yahoNanJing
I remember in the past we had some discussion with and come up a solution for this.
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[GitHub] [arrow-ballista] thinkharderdev closed issue #655: Issues with lost executor handling
Posted by "thinkharderdev (via GitHub)" <gi...@apache.org>.
thinkharderdev closed issue #655: Issues with lost executor handling
URL: https://github.com/apache/arrow-ballista/issues/655
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[GitHub] [arrow-ballista] mingmwang commented on issue #655: Issues with lost executor handling
Posted by "mingmwang (via GitHub)" <gi...@apache.org>.
mingmwang commented on issue #655:
URL: https://github.com/apache/arrow-ballista/issues/655#issuecomment-1418576039
I will take a look.
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[GitHub] [arrow-ballista] thinkharderdev commented on issue #655: Issues with lost executor handling
Posted by "thinkharderdev (via GitHub)" <gi...@apache.org>.
thinkharderdev commented on issue #655:
URL: https://github.com/apache/arrow-ballista/issues/655#issuecomment-1424191101
@yahoNanJing @mingmwang I prototyped something on our fork here https://github.com/coralogix/arrow-ballista/commit/9887f7757f33225769de52874ef10aa7fa6e4b57
The basic gist is:
1. Add a new executor status `Fenced` indicating executor is shutting down
2. When executor begins shutdown, immediately send a heartbeat with status `Fenced`
3. Schedulers should only consider executors with `Active` status as alive.
4. Executor still sends `executor_stopped` rpc immediately when it begin shutdown
5. But when the scheduler receives that rpc is waits a configurable amount of time (default 30s) before removing the executor
If this seems sensible I can work on upstreaming it.
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