OpenTracing Bridge: allow more generic carriers

[bboreham]

Instead of insisting that the carrier is an HTTPHeaders, cast it or adapt it to the interface we need - TextMapCarrier.

~It's a bit long-winded to wrap the read and write side separately, but this gives maximum flexibility.~

Fixes #2137 - @kvrhdn has used this fork to create a working program.

[codecov[bot]]

Codecov Report

Merging #2141 (8c48780) into main (1884de2) will increase coverage by 0.2%. The diff coverage is 78.7%.

@@           Coverage Diff           @@
##            main   #2141     +/-   ##
=======================================
+ Coverage   75.7%   75.9%   +0.2%     
=======================================
  Files        178     178             
  Lines      11703   11740     +37     
=======================================
+ Hits        8864    8922     +58     
+ Misses      2614    2584     -30     
- Partials     225     234      +9     

Impacted Files	Coverage Δ
bridge/opentracing/bridge.go	53.1% <78.7%> (+9.5%)	:arrow_up:
sdk/trace/batch_span_processor.go	80.2% <0.0%> (-1.0%)	:arrow_down:
exporters/jaeger/jaeger.go	91.1% <0.0%> (+0.8%)	:arrow_up:

[kvrhdn]

I can confirm this fixes our issue, propagation context can be injected and extracted without error now 🙂

[hickeyma]

Ping @bboreham. Rebase needed and some feedback to look at.

[bboreham]

Ack. It hasn't been high enough up my priority list lately.

[bboreham]

Rebased and added unit tests for the Inject/Extract functionality added in this PR.

Note that ot.HTTPHeadersCarrier needs special treatment - Set() modifies the keys to meet HTTP header expectations - so we can't use the generic wrapper I added in that case.

It appears baggage was never propagated by BridgeTracer, so that is not included in the test.

[Aneurysm9]

Does https://github.com/open-telemetry/opentelemetry-go/pull/2911 meet the needs here, or is there more required?

[bboreham]

Does https://github.com/open-telemetry/opentelemetry-go/pull/2911 meet the needs here

Strictly no, however I think #2911 makes it easier to work around the deficiency.

~Perhaps you will update the doc says it should work with TextMapWriter?~ EDIT that doc is in OpenTracing so I realise OpenTelemetry would not update it.

Do you have any response to https://github.com/open-telemetry/opentelemetry-go/pull/2141#issuecomment-1101314799 ?

[zalegrala]

@MrAlias Do you have any further feedback for this PR please?