Re: CQLSSTableWriter memory leak

[Xu Zhongxing]

We figured out the reason for the growing memory usage. When adding rows, if 
flush-to-disk operation is done in SStableSimpleUnsortedWriter.newRow(). But 
for the compound primary key case, when the clustering key is identical, there 
is no new row created. So the single huge row is kept in the memory and no disk 
sync() is done.






在 2014-06-06 00:16:13，"Jack Krupansky" <j...@basetechnology.com> 写道：

How many rows (primary key values) are you writing for each partition of the 
primary key? I mean, are there relatively few, or are these very wide 
partitions?
 
Oh, I see! You’re writing 50,000,000 rows to a single partition! My, that IS 
ambitious.
 
-- Jack Krupansky
 
From:Xu Zhongxing
Sent: Thursday, June 5, 2014 3:34 AM
To:user@cassandra.apache.org
Subject: CQLSSTableWriter memory leak
 

I am using Cassandra's CQLSSTableWriter to import a large amount of data into 
Cassandra. When I use CQLSSTableWriter to write to a table with compound 
primary key, the memory consumption keeps growing. The GC of JVM cannot collect 
any used memory. When writing to tables with no compound primary key, the JVM 
GC works fine.

My Cassandra version is 2.0.5. The OS is Ubuntu 14.04 x86-64. JVM parameters 
are -Xms1g -Xmx2g. This is sufficient for all other non-compound primary key 
cases.

The problem can be reproduced by the following test case:

import org.apache.cassandra.io.sstable.CQLSSTableWriter;
import org.apache.cassandra.exceptions.InvalidRequestException;

import java.io.IOException;
import java.util.UUID;

class SS {
    public static void main(String[] args) {
        String schema = "create table test.t (x uuid, y uuid, primary key (x, 
y))";


        String insert = "insert into test.t (x, y) values (?, ?)";
        CQLSSTableWriter writer = CQLSSTableWriter.builder()
            .inDirectory("/tmp/test/t")
            .forTable(schema).withBufferSizeInMB(32)
            .using(insert).build();

        UUID id = UUID.randomUUID();
        try {
            for (int i = 0; i < 50000000; i++) {
                UUID id2 = UUID.randomUUID();
                writer.addRow(id, id2);
            }

            writer.close();
        } catch (Exception e) {
            System.err.println("hell");
        }
    }
}