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From "Daniel Doubleday (Created) (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-4065) Bogus MemoryMeter liveRatio calculations
Date Tue, 20 Mar 2012 08:39:45 GMT
Bogus MemoryMeter liveRatio calculations
----------------------------------------

                 Key: CASSANDRA-4065
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4065
             Project: Cassandra
          Issue Type: Bug
          Components: Core
    Affects Versions: 1.0.8
            Reporter: Daniel Doubleday
            Priority: Minor


I get strange cfs.liveRatios.

A couple of mem meter runs seem to calculate bogus results: 

{noformat}
Tue 09:14:48 dd@blnrzh045:~$ grep 'setting live ratio to maximum of 64 instead of' /var/log/cassandra/system.log
 WARN [MemoryMeter:1] 2012-03-20 08:08:07,253 Memtable.java (line 193) setting live ratio
to maximum of 64 instead of Infinity
 WARN [MemoryMeter:1] 2012-03-20 08:08:09,160 Memtable.java (line 193) setting live ratio
to maximum of 64 instead of Infinity
 WARN [MemoryMeter:1] 2012-03-20 08:08:13,274 Memtable.java (line 193) setting live ratio
to maximum of 64 instead of Infinity
 WARN [MemoryMeter:1] 2012-03-20 08:08:22,032 Memtable.java (line 193) setting live ratio
to maximum of 64 instead of Infinity
 WARN [MemoryMeter:1] 2012-03-20 08:12:41,057 Memtable.java (line 193) setting live ratio
to maximum of 64 instead of 67.11787351054079
 WARN [MemoryMeter:1] 2012-03-20 08:13:50,877 Memtable.java (line 193) setting live ratio
to maximum of 64 instead of 112.58547951925435
 WARN [MemoryMeter:1] 2012-03-20 08:15:29,021 Memtable.java (line 193) setting live ratio
to maximum of 64 instead of 193.36945063589877
 WARN [MemoryMeter:1] 2012-03-20 08:17:50,716 Memtable.java (line 193) setting live ratio
to maximum of 64 instead of 348.45008340969434
{noformat}

Because meter runs never decrease liveRatio in Memtable (Which seems strange to me. If past
calcs should be included for any reason wouldn't averaging make more sense?):

{noformat}
cfs.liveRatio = Math.max(cfs.liveRatio, newRatio);
{noformat}

Memtables are flushed every couple of secs:

{noformat}
ColumnFamilyStore.java (line 712) Enqueuing flush of Memtable-BlobStore@935814661(1874540/149963200
serialized/live bytes, 202 ops)
{noformat}

Even though a saner liveRatio has been calculated after the bogus runs:

{noformat}
INFO [MemoryMeter:1] 2012-03-20 08:19:55,934 Memtable.java (line 198) CFS(Keyspace='SmeetBlob',
ColumnFamily='BlobStore') 
   liveRatio is 64.0 (just-counted was 2.97165811895841).  calculation took 124ms for 58 columns
{noformat}

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