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Todd Lipcon commented on HDFS-767: ---------------------------------- Hi Ning, The formula seems reasonable but slightly more complicated than necessary. Why not simply use truncated binary exponential backoff like ethernet? http://en.wikipedia.org/wiki/Truncated_binary_exponential_backoff - this formula is well known and proven to be effective for similar situations. > Job failure due to BlockMissingException > ---------------------------------------- > > 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. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.