[Impala-ASF-CR] IMPALA-4671: (part-2) Replace kudu::ServicePool with one that uses Impala threads

["Sailesh Mukil (Code Review)" <ge...@cloudera.org>]

Sailesh Mukil has uploaded a new patch set (#3). ( http://gerrit.cloudera.org:8080/8472 )

Change subject: IMPALA-4671: (part-2) Replace kudu::ServicePool with one that uses Impala threads
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IMPALA-4671: (part-2) Replace kudu::ServicePool with one that uses Impala threads

The KuduRPC subsystem uses kudu::ServicePool to service all incoming
RPCs. Since this lives inside the Kudu codebase, all instrumentation
of RPCs flowing through the KuduRPC subsystem is not visible to Impala,
as Kudu does not export this instrumentation, but only maintains it
internally within kudu::ServicePool.

In order to reliably view the instrumentation of all RPCs flowing through
KRPC, one option is to modify kudu::ServicePool to take their
instrumentation and display it on our webpages, which is very invasive.

A second option is to have a parallel implementation of kudu::ServicePool
which for all purposes behaves the same way, but instead has this extra
code that displays this instrumentation in our webpages.

This patch is Part 2 of the second option.

In Part 1, we simply copied the code from kudu::ServicePool into the Impala
namespace. In this patch, we rename the redundant kudu::ServicePool
(that was copied into be/src/rpc/) to ImpalaServicePool. We also expose
the instrumentaion of the ImpalaServicePool as JSON.

This patch also enables the tracking of the RpcMgr via the Webserver. The
RpcMgr calls into the active ImpalaServicePool objects and retrieves their
instrumentation as JSON and makes it available in the Impala webpage.

Finally, the threads in use by the service pool will also be visible in
the /threadz page.

A screenshot of the new additions to the /rpcz page is here:
https://ibb.co/nciLDG

This patch is partially based on an abandoned patch by Henry Robinson.

Change-Id: Ia3e0fa9ae22c4803b0cea736eb35e333e2671448
---
M be/src/rpc/CMakeLists.txt
M be/src/rpc/impala-service-pool.cc
M be/src/rpc/impala-service-pool.h
M be/src/rpc/rpc-mgr.cc
M be/src/rpc/rpc-mgr.h
M be/src/rpc/rpc-trace.cc
M be/src/rpc/rpc-trace.h
M be/src/service/impalad-main.cc
M www/rpcz.tmpl
9 files changed, 411 insertions(+), 139 deletions(-)


  git pull ssh://gerrit.cloudera.org:29418/Impala-ASF refs/changes/72/8472/3
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Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: newpatchset
Gerrit-Change-Id: Ia3e0fa9ae22c4803b0cea736eb35e333e2671448
Gerrit-Change-Number: 8472
Gerrit-PatchSet: 3
Gerrit-Owner: Sailesh Mukil <sa...@cloudera.com>