Automatically set GOMAXPROCS

[rubenvp8510]

Which problem is this PR solving?

• Fixes Issue Enable adding user-defined environment variables to collector/query jaeger-operator#396

Short description of the changes

• This PR set the GOMXPROCS to an automatic valid depending of the containers limits.

Does we need to make this configurable? I mean enable/disable using flags? @pavolloffay @objectiser

[objectiser]

@yurishkuro This is probably one you should answer, especially as it is using the Uber automaxprocs package? Would you prefer it configurable or enabled all the time?

[pavolloffay]

@rubenvp8510 did you test it on k8s? Does it use resource requests or limits?

[codecov]

Codecov Report

Merging #1560 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1560   +/-   ##
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  Coverage   98.79%   98.79%           
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  Files         190      190           
  Lines        9063     9063           
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  Hits         8954     8954           
  Misses         85       85           
  Partials       24       24

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[yurishkuro]

@objectiser it makes sense, when we build collector internally we're also using this module to adjust GOMAXPROCS

[rubenvp8510]

@pavolloffay Yes I did some tests and the library uses limits if they are defined.

With:

          resources:
            requests:
              memory: "64Mi"
              cpu: "250m"
            limits:
              memory: "128Mi"
              cpu: "2000m"

I got this:

2019/05/24 17:28:19 maxprocs: Updating GOMAXPROCS=2: determined from CPU quota

@yurishkuro should I leave this as it is? Or should I add a flag to enable/disable this behaviour?

[yurishkuro]

I think we should merge it. If someone needs this configurable in the future, they can create another issue.