[Impala-ASF-CR] WIP IMPALA-7550 Add documentation to profile counters

["Lars Volker (Code Review)" <ge...@cloudera.org>]

Hello Philip Zeyliger, Tim Armstrong, Impala Public Jenkins, 

I'd like you to reexamine a change. Please visit

    http://gerrit.cloudera.org:8080/12116

to look at the new patch set (#2).

Change subject: WIP IMPALA-7550 Add documentation to profile counters
......................................................................

WIP IMPALA-7550 Add documentation to profile counters

This is a prototype, I'm looking for feedback on the overall approach.

This change adds a singleton registry for runtime profile counters
prototypes, similar to what Kudu does for metrics. That allows us to
print documentation for all profile counters. As an example, this change
adds a debug webpage /profile_docs. With that we can also generate
documentation for all profile counters. In a future change we can then
add tooltips to the profile view directly.

Profile counters are annotated with their stability:

* Stable counters - generally useful to understand query performance,
should only change rarely and if it does we'll make some effort to
notify users. E.g. BytesRead.
* Unstable but useful - useful to understand query performance, but
subject to change, particularly if the implementation changes. E.g.
RowBatchQueuePutWaitTime, MaterializeTupleTimer
* Debugging counters - generally not useful to users of Impala, the main
use case is low-level debugging. Can be hidden to reduce noise for most
consumers of profiles.

The downside is that we'd reduce the comments that currently explain
some of the counters in header files by moving them to the .cc files.
Additionally a (arguably good) limitation is that profile counter names
need to be unique.

Change-Id: I1f088227b03fca19b0efee6c390f30de0b327226

End of prototype

Mention profile_docs

Change-Id: Idaa0a44f0a996f3487566b545d984d562e6e1588
---
M be/src/exec/scan-node.cc
M be/src/exec/scan-node.h
M be/src/runtime/coordinator.cc
M be/src/runtime/coordinator.h
D be/src/util/debug-counters.h
M be/src/util/default-path-handlers.cc
M be/src/util/runtime-profile-counters.h
M be/src/util/runtime-profile.cc
M www/query_profile.tmpl
9 files changed, 192 insertions(+), 93 deletions(-)


  git pull ssh://gerrit.cloudera.org:29418/Impala-ASF refs/changes/16/12116/2
-- 
To view, visit http://gerrit.cloudera.org:8080/12116
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Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: newpatchset
Gerrit-Change-Id: Idaa0a44f0a996f3487566b545d984d562e6e1588
Gerrit-Change-Number: 12116
Gerrit-PatchSet: 2
Gerrit-Owner: Lars Volker <lv...@cloudera.com>
Gerrit-Reviewer: Impala Public Jenkins <im...@cloudera.com>
Gerrit-Reviewer: Philip Zeyliger <ph...@cloudera.com>
Gerrit-Reviewer: Tim Armstrong <ta...@cloudera.com>