Job failure due to BlockMissingException
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Key: HDFS-767
URL: https://issues.apache.org/jira/browse/HDFS-767
Project: Hadoop HDFS
Issue Type: Improvement
Reporter: Ning Zhang
If a block is request by too many mappers/reducers (say, 3000) at the same
time, a BlockMissingException is thrown because it exceeds the upper limit (I
think 256 by default) of number of threads accessing the same block at the same
time. The DFSClient wil catch that exception and retry 3 times after waiting
for 3 seconds. Since the wait time is a fixed value, a lot of clients will
retry at about the same time and a large portion of them get another failure.
After 3 retries, there are about 256*4 = 1024 clients got the block. If the
number of clients are more than that, the job will fail.
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