Provide `db.operation` and `db.system` at span start so it can be used for sampling decisions

[trask]

Description

It looks like the old semantic conventions (which the library follows) didn't specify any database attributes as sampling relevant, but the new semantic conventions do (though these are renamed in the new semantic conventions).

elasticsearch-java/java-client/src/main/java/co/elastic/clients/transport/instrumentation/OpenTelemetryForElasticsearch.java

Lines 188 to 191 in c027cda

	span = tracer.spanBuilder(endpointId).setSpanKind(SpanKind.CLIENT).startSpan();
	if (span.isRecording()) {
	span.setAttribute(ATTR_DB_SYSTEM, "elasticsearch");
	span.setAttribute(ATTR_DB_OPERATION, endpointId);

[l-trotta]

Hello @trask, after this PR which was applied in version 9.1.0 of the client, the client should follow the new semantic conventions. Did we miss anything?

[trask]

hi @l-trotta!

sorry, I missed that the constant values reflect the new semconv 👍

check out this section in the new semconv (which is unfortunately a bit buried currently):

The following attributes can be important for making sampling decisions and SHOULD be provided at span creation time (if provided at all):

• ...
• db.operation.name
• ...
• db.system.name
• ...

For these to be available to samplers, they would need to be passed to the SpanBuilder before calling startSpan().

[l-trotta]

@trask I had no idea, thank you for letting me know! it will be updated soon and out in the next releases/patches