server/api: add an API to configure failpoints in runtime

[sticnarf]

What is changed and how it works?

It would be easier to construct test cases if we could configure failpoint in runtime. Both TiKV and TiDB support such an API.

This PR adds /pd/api/v1/fail/ to configure failpoints.

Check List

Tests

• Manual test (add detailed scripts or steps below)

First set GO_FAILPOINTS="github.com/tikv/pd/server/api/enableFailpointAPI=return" environment variable to enable this API.

Then, we can run HTTP requests like this to set failpoints:

curl -X PUT -d "return" http://{PD_ADDR}:2379/pd/api/v1/fail/github.com/tikv/pd/server/tso/systemTimeSlow

And we can also get the enabled failpoint list:

❯ curl http://{PD_ADDR}:2379/pd/api/v1/fail/
github.com/tikv/pd/server/api/enableFailpointAPI=return
github.com/tikv/pd/server/tso/systemTimeSlow=return

Code changes

• Has HTTP API interfaces change

Release note

• No release note.

[codecov]

Codecov Report

Merging #3488 (27e57a6) into master (b4813a2) will increase coverage by 0.01%.
The diff coverage is 33.33%.

@@            Coverage Diff             @@
##           master    #3488      +/-   ##
==========================================
+ Coverage   74.50%   74.52%   +0.01%     
==========================================
  Files         244      244              
  Lines       24034    24039       +5     
==========================================
+ Hits        17907    17915       +8     
- Misses       4508     4512       +4     
+ Partials     1619     1612       -7     

Flag	Coverage Δ
unittests	74.52% <33.33%> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
server/api/router.go	97.05% <33.33%> (-2.34%)	⬇️
pkg/tempurl/tempurl.go	60.00% <0.00%> (-10.00%)	⬇️
server/tso/local_allocator.go	73.23% <0.00%> (-7.05%)	⬇️
server/tso/global_allocator.go	70.80% <0.00%> (-6.57%)	⬇️
server/election/lease.go	89.83% <0.00%> (-5.09%)	⬇️
server/tso/allocator_manager.go	75.08% <0.00%> (-1.83%)	⬇️
pkg/btree/btree.go	85.30% <0.00%> (-0.97%)	⬇️
server/grpc_service.go	47.42% <0.00%> (-0.68%)	⬇️
client/client.go	72.33% <0.00%> (-0.29%)	⬇️
client/base_client.go	83.78% <0.00%> (+0.54%)	⬆️
... and 11 more

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[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• JmPotato
• nolouch

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[JmPotato]

/merge

[ti-chi-bot]

@JmPotato: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

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[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 9126856