GitHub user rdblue opened a pull request:
https://github.com/apache/spark/pull/17813
[SPARK-20540][CORE] Fix unstable executor requests.
There are two problems fixed in this commit. First, the
ExecutorAllocationManager sets a timeout to avoid requesting executors
too often. However, the timeout is always updated based on its value and
a timeout, not the current time. If the call is delayed by locking for
more than the ongoing scheduler timeout, the manager will request more
executors on every run. This seems to be the main cause of SPARK-20540.
The second problem is that the total number of requested executors is
not tracked by the CoarseGrainedSchedulerBackend. Instead, it calculates
the value based on the current status of 3 variables: the number of
known executors, the number of executors that have been killed, and the
number of pending executors. But, the number of pending executors is
never less than 0, even though there may be more known than requested.
When executors are killed and not replaced, this can cause the request
sent to YARN to be incorrect because there were too many executors due
to the scheduler's state being slightly out of date. This is fixed by
tracking
the currently requested size explicitly.
## How was this patch tested?
Existing tests.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/rdblue/spark
SPARK-20540-fix-dynamic-allocation
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/17813.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #17813
----
commit 96a76868abe168d17b24011d9090cb495c8c1c3f
Author: Ryan Blue <[email protected]>
Date: 2017-04-24T18:42:57Z
SPARK-20540: Fix unstable executor requests.
There are two problems fixed in this commit. First, the
ExecutorAllocationManager sets a timeout to avoid requesting executors
too often. However, the timeout is always updated based on its value and
a timeout, not the current time. If the call is delayed by locking for
more than the ongoing scheduler timeout, the manager will request more
executors on every run.
The second problem is that the total number of requested executors is
not tracked by the CoarseGrainedSchedulerBackend. Instead, it calculates
the value based on the current status of 3 variables: the number of
known executors, the number of executors that have been killed, and the
number of pending executors. But, the number of pending executors is
never less than 0, even though there may be more known than requested.
When executors are killed and not replaced, this can cause the request
sent to YARN to be incorrect because there were too many executors due
to the scheduler's state being slightly out of date.
----
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