[close #635] constraint the getMember timeout by inject a backoffer

[iosmanthus]

Signed-off-by: iosmanthus myosmanthustree@gmail.com

What problem does this PR solve?

Issue Number: close #635

Problem Description:

The getMembers is not limited by a backoffer, which might cause the exception will not throw in time. For example, a user might set the timeout of a request to 400ms, but if the PD is disconnected, the getMembers might sleep more than 400ms since the backoffer it used is not passed from the upper code.

What is changed and how does it work?

Inject a backoffer for getMembers and check timeout before acquiring a channel from the pool.

Check List for Tests

This PR has been tested by at least one of the following methods:

• Unit test

Related changes

• Need to cherry-pick the release branch

[codecov]

Codecov Report

Merging #636 (95f9b92) into master (2ae746d) will increase coverage by 0.28%.
The diff coverage is 57.14%.

@@             Coverage Diff              @@
##             master     #636      +/-   ##
============================================
+ Coverage     34.68%   34.96%   +0.28%     
- Complexity     1420     1435      +15     
============================================
  Files           278      278              
  Lines         17358    17361       +3     
  Branches       1972     1974       +2     
============================================
+ Hits           6020     6071      +51     
+ Misses        10726    10675      -51     
- Partials        612      615       +3     

Impacted Files	Coverage Δ
.../main/java/org/tikv/common/AbstractGRPCClient.java	49.35% <ø> (+7.04%)	⬆️
...java/org/tikv/common/operation/PDErrorHandler.java	38.70% <50.00%> (ø)
src/main/java/org/tikv/common/PDClient.java	64.75% <58.33%> (+7.93%)	⬆️
...g/tikv/common/operation/iterator/ScanIterator.java	76.31% <0.00%> (-2.64%)	⬇️
...ty/handler/codec/http2/Http2ConnectionHandler.java	48.65% <0.00%> (-2.45%)	⬇️
src/main/java/io/grpc/internal/ClientCallImpl.java	57.07% <0.00%> (+0.24%)	⬆️
...rc/main/java/io/grpc/netty/NettyClientHandler.java	56.89% <0.00%> (+0.64%)	⬆️
...n/java/org/tikv/common/util/ConcreteBackOffer.java	84.68% <0.00%> (+0.90%)	⬆️
src/main/java/org/tikv/common/TiConfiguration.java	70.82% <0.00%> (+3.45%)	⬆️
... and 1 more

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[ti-srebot]

@zhangyangyu, Thanks for your review. The bot only counts LGTMs from Reviewers and higher roles, but you're still welcome to leave your comments. You are not a reviewer or committer or co-leader or leader.

[sunxiaoguang]

LGTM

[ti-srebot]

cherry pick to release-3.3 in PR #637