Steve Loughran created HADOOP-13695:
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Summary: S3A to use a thread pool for async path operations
Key: HADOOP-13695
URL: https://issues.apache.org/jira/browse/HADOOP-13695
Project: Hadoop Common
Issue Type: Sub-task
Components: fs/s3
Affects Versions: 2.8.0
Reporter: Steve Loughran
S3A path operations are often slow due to directory scanning, mock directory
create/delete, etc. Many of these can be done asynchronously
* because deletion is eventually consistent, deleting parent dirs after an
operation has returned doesn't alter the behaviour, except in the special case
of : operation failure.
* scanning for paths/parents of a file in the create operation only needs to
complete before the close() operation instantiates the object, no need to block
create().
* parallelized COPY calls would permit asynchronous rename.
We could either use the thread pool used for block writes, or somehow isolate
low cost path ops (GET, DELETE) from the more expensive calls (COPY, PUT) so
that a thread doing basic IO doesn't block for the duration of the long op.
Maybe also use {{Semaphore.tryAcquire()}} and only start async work if there
actually is an idle thread, doing it synchronously if not. Maybe it depends on
the operation. path query/cleanup before/after a write is something which could
be scheduled as just more futures to schedule in the block write.
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