Custom should_trace predicate in opentracing extensions

[studzien]

Hey 👋

This is my take on #859.

At Whatnot, we are facing a similar problem to the one described, where we have a few resolvers implemented on some custom types.
The penalty for tracing every single resolver, especially on a long list, is very significant, and we're hoping to reduce response times by not generating spans for some of them.

[codecov]

Codecov Report

Merging #1066 (0e086f0) into master (a9f0427) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1066      +/-   ##
==========================================
+ Coverage   98.11%   98.12%   +0.01%     
==========================================
  Files         115      115              
  Lines        7377     7421      +44     
==========================================
+ Hits         7238     7282      +44     
  Misses        139      139              

Impacted Files	Coverage Δ
ariadne/contrib/tracing/opentracing.py	96.00% <100.00%> (+0.21%)	⬆️
tests/tracing/test_opentracing.py	100.00% <100.00%> (ø)
tests/tracing/test_opentracing_sync.py	100.00% <100.00%> (ø)

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[rafalp]

Thanks for opening a PR. I'll flag this with decision needed because I would like to explore some ideas for faster middlewares first before committing to this option.

[rafalp]

The penalty for tracing every single resolver, especially on a long list, is very significant, and we're hoping to reduce response times by not generating spans for some of them.

Most of penalty for tracing comes from asynchronous middleware making all field resolutions in graphql query executor asynchronous. async/await overhead is non-negligible when there are thousands of resolver calls.

But you may have some noise resolvers you may want to exclude from tracing anyway, so we could support that. However we are deprecating opentracing because the standard was declared deprecated and superseded by opentelemetry, for which we will be adding an extension in next Ariadne release.

[rafalp]

Closing this for lack of activity. @studzien if you want to update this PR to work for both OpenTracing and OpenTelemetry, please let me know here and I'll reopen this 😄