Remote sampling support - AWS X-Ray

[bhautikpip]

This PR introduces remote sampling support using AWS X-Ray. This implementation uses 2 X-Ray APIs as mentioned below.

1. getSamplingRules (retrieve customer set rules on AWS X-Ray console)
2. getSamplingTargets (retrieve targets assigned to each client for each rule but API request should also send a snapshot on how many requests are sample, borrowed and matched using each rule)

Reference docs for some of the data structures used in implementation
https://docs.aws.amazon.com/xray/latest/devguide/xray-console-sampling.html#xray-console-config
https://docs.aws.amazon.com/xray/latest/api/API_GetSamplingRules.html
https://docs.aws.amazon.com/xray/latest/api/API_GetSamplingTargets.html

[codecov]

Codecov Report

Merging #1859 (1fc8df8) into main (5611141) will increase coverage by 0.8%.
The diff coverage is 75.3%.

@@           Coverage Diff           @@
##            main   #1859     +/-   ##
=======================================
+ Coverage   68.5%   69.4%   +0.8%     
=======================================
  Files        124     135     +11     
  Lines       5366    6113    +747     
=======================================
+ Hits        3680    4243    +563     
- Misses      1582    1742    +160     
- Partials     104     128     +24     

Impacted Files	Coverage Δ
samplers/aws/xray/timer.go	0.0% <0.0%> (ø)
samplers/aws/xray/remote_sampler.go	2.1% <2.1%> (ø)
samplers/aws/xray/rand.go	23.0% <23.0%> (ø)
samplers/aws/xray/internal/client.go	79.6% <79.6%> (ø)
samplers/aws/xray/internal/rule.go	82.2% <82.2%> (ø)
samplers/aws/xray/internal/manifest.go	90.2% <90.2%> (ø)
samplers/aws/xray/remote_sampler_config.go	91.4% <91.4%> (ø)
samplers/aws/xray/internal/match.go	92.3% <92.3%> (ø)
samplers/aws/xray/fallback_sampler.go	97.8% <97.8%> (ø)
samplers/aws/xray/internal/clock.go	100.0% <100.0%> (ø)
... and 1 more

[bhautikpip]

@anuraaga @MrAlias @jmacd @Aneurysm9 Can you review this PR? I have closed the older one and opened a fresh PR with complete remote sampling support and tried to address most of the concerns/comments we have discussed. Feel free to take a look again. Thanks!

[hanyuancheung]

PTAL at the suggestion.

[bhautikpip]

While running the make precommit I have started receiving this error. There is some checksum mis match in deps of tools module. Are we planning to fix this issue as part of the other PR ?

bhautip@38f9d362ae67 opentelemetry-go-contrib % make precommit     
cd ./tools && \
        go build -o /Users/bhautip/Documents/lambda/opentelemetry-go-contrib/.tools/dbotconf go.opentelemetry.io/build-tools/dbotconf
verifying github.com/blizzy78/varnamelen@v0.6.1/go.mod: checksum mismatch
        downloaded: h1:mGBHm+Uo4e8JnZEKHRoZgVEOQdSBdQfY/x+k4NAXBWA=
        go.sum:     h1:zy2Eic4qWqjrxa60jG34cfL0VXcSwzUrIx68eJPb4Q8=

[Aneurysm9]

That version should be retracted. Not sure why it is being used. You may be able to work around it temporarily by putting an exclude directive for it in tools/go.mod.

[MrAlias]

One final unresolved issue as far as I see: #1859 (comment)

Otherwise this is looking good 👍

[bhautikpip]

Also, not sure why linter check is failing. I'm able to run it in my local. Maybe re-running it would be helpful since it's some timeout issue.

[bhautikpip]

@MrAlias can you run tests again? looks like some flaky test failure. If you don't have further comments we would be okay to merge this?

[MrAlias]

@MadVikingGod PTAL

[bhautikpip]

@MadVikingGod Can you take a look again to see if you have further comments on this PR or this is good to merge?

[Aneurysm9]

I spoke with @MadVikingGod and he's good with this proceeding. He will ask for follow-up PRs if he has any concerns that need to be addressed.