Lars Volker has uploaded this change for review. ( 
http://gerrit.cloudera.org:8080/12225


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

The latest PS:
* Experiments with making the PROFILE_* counters callable, e.g.
  PROFILE_BytesRead(runtime_profile()) instead of having an Instantiate
  method.
* Shows how to replace a string constant with the counter name
* Replaces all counters in scan-node and hdfs-scan-node-base

Open questions are:

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

WIP

Change-Id: I04fb00c0d055d3151b98ce2c9c74e2245f58725d
---
M be/src/exec/hdfs-scan-node-base.cc
M be/src/exec/scan-node.cc
M be/src/exec/scan-node.h
M be/src/runtime/coordinator-backend-state.cc
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
10 files changed, 517 insertions(+), 151 deletions(-)



  git pull ssh://gerrit.cloudera.org:29418/Impala-ASF refs/changes/25/12225/1
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Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: newchange
Gerrit-Change-Id: I04fb00c0d055d3151b98ce2c9c74e2245f58725d
Gerrit-Change-Number: 12225
Gerrit-PatchSet: 1
Gerrit-Owner: Lars Volker <[email protected]>

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