Discussion: Supporting OTLP protocol directly about pg_tracing

[bonnefoa]

I'm leaning towards the libcurl approach myself. What do you think?

I would definitely prefer this over adding opentelemetry-cpp as a dependency. I took a stab at implementing it in #27 and was able to send json spans with libcurl through OTLP/HTTP.

It currently uses a background worker that sends the spans to a defined otel collector at regular intervals (function to trigger sending spans or sending spans when buffer is x% full could be added later on). This allows to keep curl usage in a dedicated process and simplify sharing a single connection to the otel exporter for the whole db.

It's nice to have something to play with, though, even when you don't have OpenTelemetry colletor

I've added the select pg_tracing_json_spans() function to output the json that would be sent to the otel collector. It is also used for testing. Most of my tests still rely very heavily on the pg_tracing_{peek,consume}_spans but it would be possible to convert them to rely on the json export instead.