[CASSANDRA-4065] Bogus MemoryMeter liveRatio calculations

• Type: Bug
• Status: Resolved
• Priority: Low
• Resolution: Fixed
• Fix Version/s: 1.1.0
• Severity: Low
• Assignee: Daniel Doubleday
• Reporter: Daniel Doubleday

Authors

Daniel Doubleday

Reviewers

Jonathan Ellis

• Created: 20/Mar/12 08:39
• Updated: 16/Apr/19 09:32
• Resolved: 18/Apr/12 23:14

Description

I get strange cfs.liveRatios.

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

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

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?):

cfs.liveRatio = Math.max(cfs.liveRatio, newRatio);

Memtables are flushed every couple of secs:

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

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

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