[
https://issues.apache.org/jira/browse/CASSANDRA-13265?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15964613#comment-15964613
]
Ariel Weisberg commented on CASSANDRA-13265:
--------------------------------------------
Squashing is preferred, but I like to keep the history. When I squash I create
a second -squashed branch to hold the squash commit. I never delete branches
and tolerate the cluttered namespace. If we used pull requests I would delete
branches since the pull request preserves the information, but we don't :-(
Since people tend to work on multiple tickets they don't name the branch
cassandra-3.0 they do something like cassandra-13625-3.0. The commit process I
follow is http://cassandra.apache.org/doc/latest/development/how_to_commit.html.
For the commit message don't list multiple reviewers just the one in the JIRA
(me). I have been told that line is automatically parsed so we want to stick to
the expected format. Also some OCD people want a line break in between the
first and last line of the commit message.
Having CHANGES.TXT in the patch is helpful so I don't forget to add it in one
branch. If it's not there and I follow the commit process I have to add it at
each branch. For the entry also include the ticket number in parens at the end.
I'll kick off the tests now.
> Expiration in OutboundTcpConnection can block the reader Thread
> ---------------------------------------------------------------
>
> Key: CASSANDRA-13265
> URL: https://issues.apache.org/jira/browse/CASSANDRA-13265
> Project: Cassandra
> Issue Type: Bug
> Environment: Cassandra 3.0.9
> Java HotSpot(TM) 64-Bit Server VM version 25.112-b15 (Java version
> 1.8.0_112-b15)
> Linux 3.16
> Reporter: Christian Esken
> Assignee: Christian Esken
> Fix For: 3.0.x
>
> Attachments: cassandra.pb-cache4-dus.2017-02-17-19-36-26.chist.xz,
> cassandra.pb-cache4-dus.2017-02-17-19-36-26.td.xz
>
>
> I observed that sometimes a single node in a Cassandra cluster fails to
> communicate to the other nodes. This can happen at any time, during peak load
> or low load. Restarting that single node from the cluster fixes the issue.
> Before going in to details, I want to state that I have analyzed the
> situation and am already developing a possible fix. Here is the analysis so
> far:
> - A Threaddump in this situation showed 324 Threads in the
> OutboundTcpConnection class that want to lock the backlog queue for doing
> expiration.
> - A class histogram shows 262508 instances of
> OutboundTcpConnection$QueuedMessage.
> What is the effect of it? As soon as the Cassandra node has reached a certain
> amount of queued messages, it starts thrashing itself to death. Each of the
> Thread fully locks the Queue for reading and writing by calling
> iterator.next(), making the situation worse and worse.
> - Writing: Only after 262508 locking operation it can progress with actually
> writing to the Queue.
> - Reading: Is also blocked, as 324 Threads try to do iterator.next(), and
> fully lock the Queue
> This means: Writing blocks the Queue for reading, and readers might even be
> starved which makes the situation even worse.
> -----
> The setup is:
> - 3-node cluster
> - replication factor 2
> - Consistency LOCAL_ONE
> - No remote DC's
> - high write throughput (100000 INSERT statements per second and more during
> peak times).
>
--
This message was sent by Atlassian JIRA
(v6.3.15#6346)
