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From Boris Yen <yulin...@gmail.com>
Subject Enormous counter problem?
Date Tue, 09 Aug 2011 05:28:06 GMT
Hi,

I am not sure if this is a bug or we use the counter the wrong way, but I
keep getting a enormous counter number in our deployment. After a few tries,
I am finally able to reproduce it. The following are the settings of my
development:
-----------------------------------------------------
I have two-node cluster with the following keyspace and column family
settings.

Cluster Information:
   Snitch: org.apache.cassandra.locator.SimpleSnitch
   Partitioner: org.apache.cassandra.dht.RandomPartitioner
   Schema versions:
63fda700-c243-11e0-0000-2d03dcafebdf: [172.17.19.151, 172.17.19.152]

Keyspace: test:
  Replication Strategy: org.apache.cassandra.locator.NetworkTopologyStrategy
  Durable Writes: true
    Options: [datacenter1:2]
  Column Families:
    ColumnFamily: testCounter (Super)
    "APP status information."
      Key Validation Class: org.apache.cassandra.db.marshal.BytesType
      Default column value validator:
org.apache.cassandra.db.marshal.CounterColumnType
      Columns sorted by:
org.apache.cassandra.db.marshal.BytesType/org.apache.cassandra.db.marshal.BytesType
      Row cache size / save period in seconds: 0.0/0
      Key cache size / save period in seconds: 200000.0/14400
      Memtable thresholds: 1.1578125/1440/247 (millions of ops/MB/minutes)
      GC grace seconds: 864000
      Compaction min/max thresholds: 4/32
      Read repair chance: 1.0
      Replicate on write: true
      Built indexes: []

Then, I use a test program based on hector to add a counter column
(testCounter[sc][column]) 1000 times. In the middle the adding process, I
intentional shut down the node 172.17.19.152. In addition to that, the test
program is smart enough to switch the consistency level from Quorum to One,
so that the following adding actions would not fail.

After all the adding actions are done, I start the cassandra
on 172.17.19.152, and I use cassandra-cli to check if the counter is correct
on both nodes, and I got a result 1001 which should be reasonable because
hector will retry once. However, when I shut down 172.17.19.151 and
after 172.17.19.152 is aware of 172.17.19.151 is down, I try to start the
cassandra on 172.17.19.151 again. Then, I check the counter again, this time
I got a result 481387 which is so wrong.

I was wondering if anyone could explain why this happens, is this a bug or
do I use the counter the wrong way?.

Regards
Boris

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