Andrew Wong has posted comments on this change. ( 
http://gerrit.cloudera.org:8080/15315 )

Change subject: [java] subprocess: add a metrics message
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Patch Set 1:

(2 comments)

http://gerrit.cloudera.org:8080/#/c/15315/1/java/kudu-subprocess/src/main/java/org/apache/kudu/subprocess/SubprocessExecutor.java
File 
java/kudu-subprocess/src/main/java/org/apache/kudu/subprocess/SubprocessExecutor.java:

PS1:
> One thing I find a little unintuitive with the current implementation is th
Yeah, I think the guiding principle here was "do as little as we can in the 
reader/writer threads since they're single-threaded". I'll need to look into 
whether we can maybe construct a SubprocessRequestPB.Builder without entirely 
deserializing the bytes on the reader thread.


http://gerrit.cloudera.org:8080/#/c/15315/1/src/kudu/subprocess/subprocess.proto
File src/kudu/subprocess/subprocess.proto:

http://gerrit.cloudera.org:8080/#/c/15315/1/src/kudu/subprocess/subprocess.proto@49
PS1, Line 49:   // Number of requests in the subprocess's inbound queue.
            :   optional int64 inbound_queue_length = 3;
            :
            :   // Number of responses in the subprocess's outbound queue.
            :   optional int64 outbound_queue_length = 4;
> "...at the time that the {request,response} was queued." presumably?
To debug slowness of a single request, a snapshot at the time of queueing is 
useful. I don't expect us to actually debug a single request in isolation 
though.

To get a gauge what the current state of the queues are in general, "as late as 
we can before sending back to C++" is useful.

Do you think it's worth adding both? A snapshot upon entering the system and a 
snapshot upon exiting the system? Or is that overkill and wasteful?



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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: I11a89fff8df23c5057c577f2aebfd40922d01e3c
Gerrit-Change-Number: 15315
Gerrit-PatchSet: 1
Gerrit-Owner: Andrew Wong <[email protected]>
Gerrit-Reviewer: Adar Dembo <[email protected]>
Gerrit-Reviewer: Andrew Wong <[email protected]>
Gerrit-Reviewer: Attila Bukor <[email protected]>
Gerrit-Reviewer: Hao Hao <[email protected]>
Gerrit-Reviewer: Kudu Jenkins (120)
Gerrit-Comment-Date: Fri, 28 Feb 2020 19:56:25 +0000
Gerrit-HasComments: Yes

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