perf(core): rework attribute serialisation

[43081j]

Does a couple of things:

• Switches to a regular for...in which is much faster than
  Object.entries
• Only retrieves the val if the key is valid
• Compares keys against "" (empty string) rather than accessing
  length
• Reuses typeof result rather than recomputing it each time

Type of change

Performance improvement

How Has This Been Tested?

Existing unit tests cover this code, and pass successfully.

Checklist:

• Followed the style guidelines of this project
• Unit tests have been added
• Documentation has been updated

[linux-foundation-easycla]

• ✅login: 43081j / name: James Garbutt / (dc7e48c)

The committers listed above are authorized under a signed CLA.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.04%. Comparing base (8ffc70d) to head (dc7e48c).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5866   +/-   ##
=======================================
  Coverage   95.04%   95.04%           
=======================================
  Files         307      307           
  Lines        7987     7991    +4     
  Branches     1614     1616    +2     
=======================================
+ Hits         7591     7595    +4     
  Misses        396      396           

Files with missing lines	Coverage Δ
...ckages/opentelemetry-core/src/common/attributes.ts	93.75% <100.00%> (+0.56%)	⬆️

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[raphael-theriault-swi]

Could you provide some comparative figures given this is for perf ?

[43081j]

here's the results from a quick benchmark locally:

benchmark                   avg (min … max) p75 / p99    (min … top 1%)
------------------------------------------- -------------------------------
sanitizeAttributes           114.91 ns/iter 115.67 ns   ▅█
                    (109.01 ns … 186.76 ns) 135.03 ns   ██
                    (110.75  b … 611.93  b) 400.31  b ▁▁███▃▃▄▅▃▂▂▂▂▁▁▁▁▁▁▁

sanitizeAttributesMain       154.84 ns/iter 156.72 ns  █
                    (150.32 ns … 251.54 ns) 170.29 ns  █▃
                    (821.69  b …   2.59 kb)   1.00 kb ▆██▄▃▃▄▄▃▂▂▃▃▂▁▂▁▁▁▁▁

summary
  sanitizeAttributes
   1.35x faster than sanitizeAttributesMain

to be honest though, a large amount of the time is lost to warn calls 🤔

i wonder if you could optimise the log proxy to compute the logger up front?

basically this:

      const logger = getGlobal('diag');
      if (!logger) return noop;
      const logFn = logger[funcName];
      return logFn;

but it'd mean if you mutate globalThis later to add log functions, they wouldn't be picked up. so maybe not