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From Manfred Muench <docma...@domainerschoice.com>
Subject Java-Client returns empty data sets after Cassandra sits for a while
Date Fri, 18 Jun 2010 09:05:15 GMT
Hi,

I have noticed the following behaviour (bug?) which I don't completely
understand:
1. start Cassandra (I'm using 0.6.2, but it also appears in 0.6.1)
2. work with it (I'm using Java thrift API)
3. let it sit for a long time (in my case: a day or more) without
issuing any command
4. go back to (2) -- but now Cassandra always returns empty data sets to
queries in Java. The command line interface works, no matter if left
open or started newly.

Here's how I connect to Cassandra (leaving exception handling out for 
better readability):

---------------------------------------------------------------------
...
import org.apache.cassandra.thrift.Cassandra;
import org.apache.thrift.protocol.TBinaryProtocol;
import org.apache.thrift.protocol.TProtocol;
import org.apache.thrift.transport.TSocket;
...

TTransport transport = new TSocket(cassandraHost, cassandraPort);
TProtocol protocol = new TBinaryProtocol(transport);
Cassandra.Client client = new Cassandra.Client(protocol);
transport.open();
...
List<KeySlice> keySlices = client.get_range_slices(...);
...
transport.flush();
transport.close();
...
---------------------------------------------------------------------

This code usually works, but after leaving Cassandra running unused for 
a couple of hours (days), this code connects fine to Cassandra, but the 
client.get_range_slices returns an empty result set.

I am not very sure, but I believe it happens after compacting. Need to 
do more tests on this one.

Does anybody know what I'm doing wrong here? Is there any kind of 
"initialisation step" that I should have taken before running queries?

If you need more (debug) information on this matter, please let me know 
how I can provide you with it. The log files didn't show anything while 
running the query. The last log message was:

  INFO [COMPACTION-POOL:1] 2010-06-18 14:07:45,882 
CompactionManager.java (line 246) Compacting []

I ran the query at around 14:20, no other message after this one.

Thanks for your help in advance!

Cheers,
Manfred

-- 
Dr. Manfred Muench
Nanjing Imperiosus Technology Co. Ltd.
Wu Xing Nian Hua Da Sha, Room 1004
134 Hanzhong Lu, Nanjing, P.R. China



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