JDBCInputFormat GC overhead limit exceeded error

[Maximilian Bode]

Hi everyone,

I am facing a problem using the JDBCInputFormat which occurred in a larger 
Flink job. As a minimal example I can reproduce it when just writing data into 
a csv after having read it from a database, i.e.

DataSet<Tuple1<String>> existingData = env.createInput(
        JDBCInputFormat.buildJDBCInputFormat()
                .setDrivername("oracle.jdbc.driver.OracleDriver")
                .setUsername(…)
                .setPassword(…)
                .setDBUrl(…)
                .setQuery("select DATA from TABLENAME")
                .finish(),
        new TupleTypeInfo<>(Tuple1.class, BasicTypeInfo.STRING_TYPE_INFO));
existingData.writeAsCsv(…);

where DATA is a column containing strings of length ~25 characters and 
TABLENAME contains 20 million rows.

After starting the job on a YARN cluster (using -tm 3072 and leaving the other 
memory settings at default values), Flink happily goes along at first but then 
fails after something like three million records have been sent by the 
JDBCInputFormat. The Exception reads "The slot in which the task was executed 
has been released. Probably loss of TaskManager …". The local taskmanager.log 
in the affected container reads
"java.lang.OutOfMemoryError: GC overhead limit exceeded
        at 
java.util.Collections$UnmodifiableCollection.iterator(Collections.java:1063)
        at 
org.jboss.netty.channel.socket.nio.NioClientBoss.processConnectTimeout(NioClientBoss.java:119)
        at 
org.jboss.netty.channel.socket.nio.NioClientBoss.process(NioClientBoss.java:83)
        at 
org.jboss.netty.channel.socket.nio.AbstractNioSelector.run(AbstractNioSelector.java:312)
        at 
org.jboss.netty.channel.socket.nio.NioClientBoss.run(NioClientBoss.java:42)
        at 
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
        at 
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
        at java.lang.Thread.run(Thread.java:744)"

Any ideas what is going wrong here?

Cheers,
Max

— 
Maximilian Bode * Junior Consultant * maximilian.b...@tngtech.com
TNG Technology Consulting GmbH, Betastr. 13a, 85774 Unterföhring
Geschäftsführer: Henrik Klagges, Christoph Stock, Dr. Robert Dahlke
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