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

Change subject: [java] subprocess: add a metrics message
......................................................................


Patch Set 1:

(1 comment)

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;
> > To get a gauge what the current state of the queues are in general, "as l
>Not following the intuition here: doesn't _any_ point in time yield "the 
>current state of the queues", as long as the point in time is consistently 
>applied (i.e. always measure at enqueue time)?

It being consistent make the metrics usable, but take this as an example:
- enqueue on inbound, req 1 (take snapshot of queues at t=1000)
- enqueue on inbound, req 2 (take snapshot of queues at t=1001)
- enqueue on inbound, req 3 (take snapshot of queues at t=1002)
- process the requests in parallel
- enqueue on outbound, resp 3
- enqueue on outbound, resp 1
- enqueue on outbound, resp 2

This sequence gives us an unstable view of the state of the queue if we want to 
use this as a Gauge metric that tracks the current length of the queue. Though 
if we want to expose this as a histogram, the ordering doesn't matter as much.



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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: Sat, 29 Feb 2020 00:20:54 +0000
Gerrit-HasComments: Yes

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