Bob Hansen created HDFS-10781:
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Summary: libhdfs++: redefine NN timeout to be "time without a
response"
Key: HDFS-10781
URL: https://issues.apache.org/jira/browse/HDFS-10781
Project: Hadoop HDFS
Issue Type: Sub-task
Reporter: Bob Hansen
In the find tool, we submit a zillion requests to the NameNode asynchronously.
As the queue on the NameNode grows, the time to response for each individual
message will increase. In the find tool, we were eventually getting timeouts
on requests, even though the NN was respoinding as fast as its little feet
could carry it.
I propose that we should redefine timeouts to be on a per-connection basis
rather than per-request. If a client has an outstanding request to the NN but
hasn't gotten a response back within n msec, it should declare the connection
dead and retry. As long as the NameNode is being responsive to the best of its
ability and providing data, we will not declare the link dead.
One potential for Failure of Least Astonishment here is that it will mean any
particular request from a client cannot be depended on to get a positive or
negative response within a fixed amount of time, but I think that may be a good
trade to make.
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