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From "Russ Hatch (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-11340) Heavy read activity on system_auth tables can cause apparent livelock
Date Sat, 09 Apr 2016 00:32:25 GMT


Russ Hatch commented on CASSANDRA-11340:

I've been attempting to reproduce this issue, but haven't had any success so far. Have tried
20 and 60 node clusters (ec2).

Using PasswordAuthenticator, CassandraAuthorizer, various values for permissions_validity_in_ms.
I've managed to get nodes up to several hundred connections, but cpu utilization always recovers
afterwards. This was with short duration connections, so perhaps this has something to do
with connection duration as well.

I'll attach my python script I was using to generate connections and create a small amount
of writes.

> Heavy read activity on system_auth tables can cause apparent livelock
> ---------------------------------------------------------------------
>                 Key: CASSANDRA-11340
>                 URL:
>             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
>  - 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.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
>  - org.apache.cassandra.auth.Auth.isExistingUser(java.lang.String) @bci=1, line=86 (Compiled
>  - 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$Dispatcher.channelRead0(,
org.apache.cassandra.transport.Message$Request) @bci=75, line=439 (Compiled frame)
>  - org.apache.cassandra.transport.Message$Dispatcher.channelRead0(,
java.lang.Object) @bci=6, line=335 (Compiled frame)
>  -,
java.lang.Object) @bci=17, line=105 (Compiled frame)
>  -
@bci=9, line=333 (Compiled frame)
>  -$700(,
java.lang.Object) @bci=2, line=32 (Compiled frame)
>  -$ @bci=8, line=324 (Compiled
>  - java.util.concurrent.Executors$ @bci=4, line=511 (Compiled frame)
>  - org.apache.cassandra.concurrent.AbstractTracingAwareExecutorService$
@bci=5, line=164 (Compiled frame)
>  - @bci=87, line=105 (Interpreted frame)
>  - @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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