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Posted to commits@cassandra.apache.org by "Aleksey Yeschenko (Jira)" <ji...@apache.org> on 2020/09/01 15:50:00 UTC
[jira] [Comment Edited] (CASSANDRA-15158) Wait for schema agreement
rather than in flight schema requests when bootstrapping
[ https://issues.apache.org/jira/browse/CASSANDRA-15158?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17188581#comment-17188581 ]
Aleksey Yeschenko edited comment on CASSANDRA-15158 at 9/1/20, 3:49 PM:
------------------------------------------------------------------------
Pushed some minor tweaks [here|https://github.com/iamaleksey/cassandra/commits/15158-review]. Made some bits more idiomatic, and changed the way in-flight requests are being kept track of.
In general, this does the job and solves the problem in the description. It doesn't, however, fully deal with storms in large clusters caused by a sequence of updates in quick succession, but, it's not intended to, either.
EDIT: the amount of synchronisation here bothers me a tiny bit, as all of it will likely have to be eventually gotten rid of, when and if TPC happens, but I can live with it.
was (Author: iamaleksey):
Pushed some minor tweaks [here|https://github.com/iamaleksey/cassandra/commits/15158-review]. Made some bits more idiomatic, and changed the way in-flight requests are being kept track of.
In general, this does the job and solves the problem in the description. It doesn't, however, fully deal with storms in large clusters caused by a sequence of updates in quick succession, but, it's not intended to, either.
> Wait for schema agreement rather than in flight schema requests when bootstrapping
> ----------------------------------------------------------------------------------
>
> Key: CASSANDRA-15158
> URL: https://issues.apache.org/jira/browse/CASSANDRA-15158
> Project: Cassandra
> Issue Type: Bug
> Components: Cluster/Gossip, Cluster/Schema
> Reporter: Vincent White
> Assignee: Blake Eggleston
> Priority: Normal
> Time Spent: 10m
> Remaining Estimate: 0h
>
> Currently when a node is bootstrapping we use a set of latches (org.apache.cassandra.service.MigrationTask#inflightTasks) to keep track of in-flight schema pull requests, and we don't proceed with bootstrapping/stream until all the latches are released (or we timeout waiting for each one). One issue with this is that if we have a large schema, or the retrieval of the schema from the other nodes was unexpectedly slow then we have no explicit check in place to ensure we have actually received a schema before we proceed.
> While it's possible to increase "migration_task_wait_in_seconds" to force the node to wait on each latche longer, there are cases where this doesn't help because the callbacks for the schema pull requests have expired off the messaging service's callback map (org.apache.cassandra.net.MessagingService#callbacks) after request_timeout_in_ms (default 10 seconds) before the other nodes were able to respond to the new node.
> This patch checks for schema agreement between the bootstrapping node and the rest of the live nodes before proceeding with bootstrapping. It also adds a check to prevent the new node from flooding existing nodes with simultaneous schema pull requests as can happen in large clusters.
> Removing the latch system should also prevent new nodes in large clusters getting stuck for extended amounts of time as they wait `migration_task_wait_in_seconds` on each of the latches left orphaned by the timed out callbacks.
>
> ||3.11||
> |[PoC|https://github.com/apache/cassandra/compare/cassandra-3.11...vincewhite:check_for_schema]|
> |[dtest|https://github.com/apache/cassandra-dtest/compare/master...vincewhite:wait_for_schema_agreement]|
>
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