Akshat Aranya created SPARK-7708:
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Summary: Incorrect task serialization with Kryo closure serializer
Key: SPARK-7708
URL: https://issues.apache.org/jira/browse/SPARK-7708
Project: Spark
Issue Type: Bug
Components: Spark Core
Affects Versions: 1.2.2
Reporter: Akshat Aranya
I've been investigating the use of Kryo for closure serialization with Spark
1.2, and it seems like I've hit upon a bug:
When a task is serialized before scheduling, the following log message is
generated:
[info] o.a.s.s.TaskSetManager - Starting task 124.1 in stage 0.0 (TID 342,
<host>, PROCESS_LOCAL, 302 bytes)
This message comes from TaskSetManager which serializes the task using the
closure serializer. Before the message is sent out, the TaskDescription (which
included the original task as a byte array), is serialized again into a byte
array with the closure serializer. I added a log message for this in
CoarseGrainedSchedulerBackend, which produces the following output:
[info] o.a.s.s.c.CoarseGrainedSchedulerBackend - 124.1 size=132
The serialized size of TaskDescription (132 bytes) turns out to be _smaller_
than serialized task that it contains (302 bytes). This implies that
TaskDescription.buffer is not getting serialized correctly.
On the executor side, the deserialization produces a null value for
TaskDescription.buffer.
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