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Date: Mon, 14 Mar 2016 16:05:33 +0000 (UTC)
From: "Nate McCall (JIRA)" <jira@apache.org>
To: commits@cassandra.apache.org
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Subject: [jira] [Commented] (CASSANDRA-11340) Heavy read activity on
 system_auth tables can cause apparent livelock
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    [ https://issues.apache.org/jira/browse/CASSANDRA-11340?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15193529#comment-15193529 ] 

Nate McCall commented on CASSANDRA-11340:
-----------------------------------------

[~jjirsa] I think the barrage of RRs triggered on a big cluster backing up the SimpleCondition's queue is the main issue. 

> Heavy read activity on system_auth tables can cause apparent livelock
> ---------------------------------------------------------------------
>
>                 Key: CASSANDRA-11340
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-11340
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Jeff Jirsa
>            Assignee: Aleksey Yeschenko
>
> Reproduced in at least 2.1.9. 
> It appears possible for queries against system_auth tables to trigger speculative retry, which causes auth to block on traffic going off node. In some cases, it appears possible for threads to become deadlocked, causing load on the nodes to increase sharply. This happens even in clusters with RF of system_auth == N, as all requests being served locally puts the bar for 99% SR pretty low. 
> Incomplete stack trace below, but we haven't yet figured out what exactly is blocking:
> {code}
> Thread 82291: (state = BLOCKED)
>  - sun.misc.Unsafe.park(boolean, long) @bci=0 (Compiled frame; information may be imprecise)
>  - java.util.concurrent.locks.LockSupport.parkNanos(long) @bci=11, line=338 (Compiled frame)
>  - org.apache.cassandra.utils.concurrent.WaitQueue$AbstractSignal.awaitUntil(long) @bci=28, line=307 (Compiled frame)
>  - org.apache.cassandra.utils.concurrent.SimpleCondition.await(long, java.util.concurrent.TimeUnit) @bci=76, line=63 (Compiled frame)
>  - org.apache.cassandra.service.ReadCallback.await(long, java.util.concurrent.TimeUnit) @bci=25, line=92 (Compiled frame)
>  - org.apache.cassandra.service.AbstractReadExecutor$SpeculatingReadExecutor.maybeTryAdditionalReplicas() @bci=39, line=281 (Compiled frame)
>  - org.apache.cassandra.service.StorageProxy.fetchRows(java.util.List, org.apache.cassandra.db.ConsistencyLevel) @bci=175, line=1338 (Compiled frame)
>  - org.apache.cassandra.service.StorageProxy.readRegular(java.util.List, org.apache.cassandra.db.ConsistencyLevel) @bci=9, line=1274 (Compiled frame)
>  - org.apache.cassandra.service.StorageProxy.read(java.util.List, org.apache.cassandra.db.ConsistencyLevel, org.apache.cassandra.service.ClientState) @bci=57, line=1199 (Compiled frame)
>  - org.apache.cassandra.cql3.statements.SelectStatement.execute(org.apache.cassandra.service.pager.Pageable, org.apache.cassandra.cql3.QueryOptions, int, long, org.apache.cassandra.service.QueryState) @bci=35, line=272 (Compiled frame)
>  - org.apache.cassandra.cql3.statements.SelectStatement.execute(org.apache.cassandra.service.QueryState, org.apache.cassandra.cql3.QueryOptions) @bci=105, line=224 (Compiled frame)
>  - org.apache.cassandra.auth.Auth.selectUser(java.lang.String) @bci=27, line=265 (Compiled frame)
>  - org.apache.cassandra.auth.Auth.isExistingUser(java.lang.String) @bci=1, line=86 (Compiled frame)
>  - org.apache.cassandra.service.ClientState.login(org.apache.cassandra.auth.AuthenticatedUser) @bci=11, line=206 (Compiled frame)
>  - org.apache.cassandra.transport.messages.AuthResponse.execute(org.apache.cassandra.service.QueryState) @bci=58, line=82 (Compiled frame)
>  - org.apache.cassandra.transport.Message$Dispatcher.channelRead0(io.netty.channel.ChannelHandlerContext, org.apache.cassandra.transport.Message$Request) @bci=75, line=439 (Compiled frame)
>  - org.apache.cassandra.transport.Message$Dispatcher.channelRead0(io.netty.channel.ChannelHandlerContext, java.lang.Object) @bci=6, line=335 (Compiled frame)
>  - io.netty.channel.SimpleChannelInboundHandler.channelRead(io.netty.channel.ChannelHandlerContext, java.lang.Object) @bci=17, line=105 (Compiled frame)
>  - io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(java.lang.Object) @bci=9, line=333 (Compiled frame)
>  - io.netty.channel.AbstractChannelHandlerContext.access$700(io.netty.channel.AbstractChannelHandlerContext, java.lang.Object) @bci=2, line=32 (Compiled frame)
>  - io.netty.channel.AbstractChannelHandlerContext$8.run() @bci=8, line=324 (Compiled frame)
>  - java.util.concurrent.Executors$RunnableAdapter.call() @bci=4, line=511 (Compiled frame)
>  - org.apache.cassandra.concurrent.AbstractTracingAwareExecutorService$FutureTask.run() @bci=5, line=164 (Compiled frame)
>  - org.apache.cassandra.concurrent.SEPWorker.run() @bci=87, line=105 (Interpreted frame)
>  - java.lang.Thread.run() @bci=11, line=745 (Interpreted frame)
> {code}
> In a cluster with many connected clients (potentially thousands), a reconnection flood (for example, restarting all at once) is likely to trigger this bug. However, it is unlikely to be seen in normal operation. 


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