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Posted to commits@cassandra.apache.org by "Michael Fong (JIRA)" <ji...@apache.org> on 2017/08/11 02:35:01 UTC
[jira] [Comment Edited] (CASSANDRA-11748) Schema version mismatch
may leads to Casandra OOM at bootstrap during a rolling upgrade process
[ https://issues.apache.org/jira/browse/CASSANDRA-11748?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16122718#comment-16122718 ]
Michael Fong edited comment on CASSANDRA-11748 at 8/11/17 2:34 AM:
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Hi, guys,
Thanks for putting some time on this issue, and this is an awesome discussion thread.
When we reported this issue a year ago, we ended up patching the C* (v2.0) with similar approach to CASSANDRA-13569, but later we found it was not addressing the root problem but putting more patches on top of one another as time goes by. In my humble opinion, I am not sure if we want to have many more types of soft/hard caps to reduce risks of running into OOM. Instead, we could probably look deeper into causes behind the current working model, such as
1. Have migration checks and requests fired asynchronously and finally stack up the all message at the receiver end merge the schema one-by-one at {code:java}Schema.instance.mergeAndAnnounceVersion(){code}
2. Send the receiver the complete copy of schema, instead of delta copy of schema out of diff between two nodes.
3. Last but not least, the most mysterious problem that leads to OOM and we could not figure out why back then, is that there are hundreds of migration task all fired nearly simultaneously, within 2 s. The number of rpcs does not match with the nodes in cluster, but is close to number of second taken for the node to reboot.
Maybe there are other tickets working to address these items already, which I may not know.
Thanks.
Michael Fong
was (Author: mcfongtw):
Hi, guys,
Thanks for putting some time on this issue, and this is an awesome discussion thread.
When we reported this issue a year ago, we ended up patching the C* (v2.0) with similar approach to CASSANDRA-13569, but later we found it was not addressing the root problem but putting more patches on top of one another as time goes by. In my humble opinion, I am not sure if we want to have many more types of soft/hard caps to reduce risks of running into OOM. Instead, we could probably look deeper into causes behind the current working model, such as
1. Have migration checks and requests fired asynchronously and finally stack up the all message at the receiver end merge the schema one-by-one at
{code:java}
Schema.instance.mergeAndAnnounceVersion()
{code}
2. Send the receiver the complete copy of schema, instead of delta copy of schema out of diff between two nodes.
3. Last but not least, the most mysterious problem that leads to OOM and we could not figure out why back then, is that there are hundreds of migration task all fired nearly simultaneously, within 2 s. The number of rpcs does not match with the nodes in cluster, but is close to number of second taken for the node to reboot.
Maybe there are other tickets working to address these items already, which I may not know.
Thanks.
Michael Fong
> Schema version mismatch may leads to Casandra OOM at bootstrap during a rolling upgrade process
> -----------------------------------------------------------------------------------------------
>
> Key: CASSANDRA-11748
> URL: https://issues.apache.org/jira/browse/CASSANDRA-11748
> Project: Cassandra
> Issue Type: Bug
> Environment: Rolling upgrade process from 1.2.19 to 2.0.17.
> CentOS 6.6
> Occurred in different C* node of different scale of deployment (2G ~ 5G)
> Reporter: Michael Fong
> Assignee: Matt Byrd
> Priority: Critical
> Fix For: 3.0.x, 3.11.x, 4.x
>
>
> We have observed multiple times when a multi-node C* (v2.0.17) cluster ran into OOM in bootstrap during a rolling upgrade process from 1.2.19 to 2.0.17.
> Here is the simple guideline of our rolling upgrade process
> 1. Update schema on a node, and wait until all nodes to be in schema version agreemnt - via nodetool describeclulster
> 2. Restart a Cassandra node
> 3. After restart, there is a chance that the the restarted node has different schema version.
> 4. All nodes in cluster start to rapidly exchange schema information, and any of node could run into OOM.
> The following is the system.log that occur in one of our 2-node cluster test bed
> ----------------------------------
> Before rebooting node 2:
> Node 1: DEBUG [MigrationStage:1] 2016-04-19 11:09:42,326 MigrationManager.java (line 328) Gossiping my schema version 4cb463f8-5376-3baf-8e88-a5cc6a94f58f
> Node 2: DEBUG [MigrationStage:1] 2016-04-19 11:09:42,122 MigrationManager.java (line 328) Gossiping my schema version 4cb463f8-5376-3baf-8e88-a5cc6a94f58f
> After rebooting node 2,
> Node 2: DEBUG [main] 2016-04-19 11:18:18,016 MigrationManager.java (line 328) Gossiping my schema version f5270873-ba1f-39c7-ab2e-a86db868b09b
> The node2 keeps submitting the migration task over 100+ times to the other node.
> INFO [GossipStage:1] 2016-04-19 11:18:18,261 Gossiper.java (line 1011) Node /192.168.88.33 has restarted, now UP
> INFO [GossipStage:1] 2016-04-19 11:18:18,262 TokenMetadata.java (line 414) Updating topology for /192.168.88.33
> ...
> DEBUG [GossipStage:1] 2016-04-19 11:18:18,265 MigrationManager.java (line 102) Submitting migration task for /192.168.88.33
> ... ( over 100+ times)
> ----------------------------------
> On the otherhand, Node 1 keeps updating its gossip information, followed by receiving and submitting migrationTask afterwards:
> INFO [RequestResponseStage:3] 2016-04-19 11:18:18,333 Gossiper.java (line 978) InetAddress /192.168.88.34 is now UP
> ...
> DEBUG [MigrationStage:1] 2016-04-19 11:18:18,496 MigrationRequestVerbHandler.java (line 41) Received migration request from /192.168.88.34.
> …… ( over 100+ times)
> DEBUG [OptionalTasks:1] 2016-04-19 11:19:18,337 MigrationManager.java (line 127) submitting migration task for /192.168.88.34
> ..... (over 50+ times)
> On the side note, we have over 200+ column families defined in Cassandra database, which may related to this amount of rpc traffic.
> P.S.2 The over requested schema migration task will eventually have InternalResponseStage performing schema merge operation. Since this operation requires a compaction for each merge and is much slower to consume. Thus, the back-pressure of incoming schema migration content objects consumes all of the heap space and ultimately ends up OOM!
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