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https://issues.apache.org/jira/browse/CASSANDRA-12461?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15513021#comment-15513021
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Alex Petrov edited comment on CASSANDRA-12461 at 9/22/16 12:37 PM:
-------------------------------------------------------------------
I've discovered several more problems while working on this patch, in the last
version (from [here|https://github.com/acoz/cassandra/commits/12461]):
* node drain code was duplicated (with minor differences, which I indicate
below), as I mentioned
* it is possible to re-start services after drain which won't run regular
shutdown path on jvm exit
* if the node was drained, under Windows the timer resolution (added in
[CASSANDRA-9634]) was not reset, since the node was considered "already
drained" (although this existed before already)
* same was happening with post-shutdown hooks in patch, since
[here|https://github.com/acoz/cassandra/blob/f15cd6d2ea95540bfacd7285dc75d9d95999e5a2/src/java/org/apache/cassandra/service/StorageService.java#L575-L576]
we'll return from runnable, since those services were shut down during
{{drain}}
[here|https://github.com/acoz/cassandra/blob/f15cd6d2ea95540bfacd7285dc75d9d95999e5a2/src/java/org/apache/cassandra/service/StorageService.java#L586-L589].
So they wouldn't run at all if {{nodetool drain}} was called.
* because logging system is shutdown in the post-shutdown hook, we depend on
the order, although we have to guarantee that logging is available for all
hooks and avoid any races or having to register hooks at the particular stage.
This is one of the reasons I was suggesting single drain process.
I also suggest disallowing re-enabling auto-compaction, binary, gossip, handoff
and thrift to ensure that we do not need to re-stop them in the final shutdown
hook. Operator can not bring the node into "working" state after drain without
restart anyways (one of the reasons is the fact that commit log is shut down by
that time), and it was most likely never intended to do so.
I've made a comparison table to make it easier to see what {{drain()}} method
was doing compared to {{drainOnShutdown}} runnable:
|| nodetool drain || shutdown drain hook |
| disables autocompaction |
|
| shuts down compaction manager | |
| recycles commitlog segment recycling |
|
| shuts down batchlog and hints earlier |
|
| | flushes only tables with
durable_writes |
| | clears set timer resolution for
windows |
I've combined the two processes, made clearer distinctions to allow running
things in {{drainOnShutdown}}. Since we can run all the items from the
{{nodetool drain}} part of the list during the normal node shutdown, the code
got a bit simpler, too (the only difference is now logging). If this
granularity is not enough, we have two more options:
* run post-shutdown hooks directly before the JVM shutdown
* have 3 stages: pre-, post- drain and pre-jvm shutdown instead
Although I prefer the current way.
Preliminary version of the update (also, CI pending):
|[12461-trunk-v2|https://github.com/ifesdjeen/cassandra/tree/12461-trunk-v2]|[dtest|http://cassci.datastax.com/job/ifesdjeen-12461-trunk-v2-dtest/]|[utest|http://cassci.datastax.com/job/ifesdjeen-12461-trunk-v2-testall/]|
(I've discussed the change "in theory" with [~slebresne], although it's still
worth for someone to take a deeper look at it, I'll ask around)
was (Author: ifesdjeen):
I've discovered several more problems while working on this patch:
* node drain code was duplicated (with minor differences, which I indicate
below)
* if the node was drained, under Windows the timer resolution (added in
[CASSANDRA-9634]) was not reset, since the node was considered "already
drained".
* same was happening with post-shutdown hooks, since
[here|https://github.com/acoz/cassandra/blob/f15cd6d2ea95540bfacd7285dc75d9d95999e5a2/src/java/org/apache/cassandra/service/StorageService.java#L575-L576]
we'll return from runnable, since those services were shut down during
{{drain}}
[here|https://github.com/acoz/cassandra/blob/f15cd6d2ea95540bfacd7285dc75d9d95999e5a2/src/java/org/apache/cassandra/service/StorageService.java#L586-L589].
This is one of the reasons I was advocating for a single consistent drain
process.
I also suggest disallowing re-enabling auto-compaction, binary, gossip, handoff
and thrift to ensure that we do not need to re-stop them in the final shutdown
hook. Operator can not bring the node into "working" state after drain without
restart anyways (one of the reasons is the fact that commit log is shut down by
that time), and it was most likely never intended to do so.
I've made a comparison table to make it easier to see what {{drain()}} method
was doing compared to {{drainOnShutdown}} runnable:
|| nodetool drain || shutdown drain hook |
| disables autocompaction |
|
| shuts down compaction manager | |
| recycles commitlog segment recycling |
|
| shuts down batchlog and hints earlier |
|
| | flushes only tables with
durable_writes |
| | clears set timer resolution for
windows |
I've combined the two processes, made clearer distinctions to allow running
things in {{drainOnShutdown}}. Since we can run all the items from the
{{nodetool drain}} part of the list during the normal node shutdown, the code
got a bit simpler, too (the only difference is now logging).
Preliminary version of the update (also, CI pending):
|[12461-trunk-v2|https://github.com/ifesdjeen/cassandra/tree/12461-trunk-v2]|[dtest|http://cassci.datastax.com/job/ifesdjeen-12461-trunk-v2-dtest/]|[utest|http://cassci.datastax.com/job/ifesdjeen-12461-trunk-v2-testall/]|
(I've discussed the change "in theory" with [~slebresne], although it's still
worth for someone to take a deeper look at it, I'll ask around)
> Add hooks to StorageService shutdown
> ------------------------------------
>
> Key: CASSANDRA-12461
> URL: https://issues.apache.org/jira/browse/CASSANDRA-12461
> Project: Cassandra
> Issue Type: Bug
> Reporter: Anthony Cozzie
> Assignee: Anthony Cozzie
> Fix For: 3.x
>
> Attachments:
> 0001-CASSANDRA-12461-add-C-support-for-shutdown-runnables.patch
>
>
> The JVM will usually run shutdown hooks in parallel. This can lead to
> synchronization problems between Cassandra, services that depend on it, and
> services it depends on. This patch adds some simple support for shutdown
> hooks to StorageService.
> This should nearly solve CASSANDRA-12011
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