Steve Loughran created HADOOP-18190:
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Summary: s3a prefetching streams to collect iostats on prefetching
operations
Key: HADOOP-18190
URL: https://issues.apache.org/jira/browse/HADOOP-18190
Project: Hadoop Common
Issue Type: Sub-task
Components: fs/s3
Affects Versions: 3.4.0
Reporter: Steve Loughran
There is a lot more happening in reads, so lot of more to collect and publish
in IO stats for us to view in a summary at the end of processes as well as get
from the stream while it is active
Some useful ones would seem to be
counters
* is in memory. using 0 or 1 here lets aggregation reports count total #of
memory cached files.
* prefetching operations executed
* errors during prefetching
gauges
* number of blocks in cache
* total size of blocks
* active prefetches
+ active memory used
duration tracking count/min/max/ave
* time to fetch a block
* time queued before the actual fetch begins
* time a reader is blocked waiting for a block fetch to complete
and some info on cache use itself
* number of blocks discarded unread
* number of prefetched blocks later used
* number of backward seeks to a prefetched block
* number of forward seeks to a prefetched block
the key ones I care about are
# memory consumption
# can we determine if cache is working (reads with cache hit) and when it is
not (misses, wasted prefetches)
# time blocked on executors
The stats need to be accessible on a stream even when closed, and aggregated
into the FS. once we get per-thread stats contexts we can publish there too and
collect in worker threads for reporting in task commits
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