All samplers are ignored as the default span context is force enabled

[oszi]

Since #159 was merged, sampler decisions are ignored (even AlwaysOffSampler) as the default span context is force enabled. It intended to solve a valid use-case but now every span context is force enabled. Unless you manually send a span context with o=0.

A quick and dirty solution could be changing trace_options.DEFAULT and span_context.DEFAULT_OPTIONS to '0'. Better yet, the default context should set o to int(sampler.should_sample(...)). However, neither solves that o=0 does not disable tracing.

[oszi]

Furthermore, GoogleCloudFormatPropagator's to_header wrongfully serializes the span context when the span_id is None (it happens) which breaks propagation of tracing options.
A fix would be something like this:

    def to_header(self, span_context: SpanContext) -> str:
        if span_context.span_id:
            trace_span_id = f"{span_context.trace_id}/{span_context.span_id}"
        else:
            trace_span_id = f"{span_context.trace_id}"

        return f"{trace_span_id};o={span_context.trace_options.trace_options_byte}"

I still have no better solution for the original issue than passing the sampler to the propagator and setting the tracing options to self.sampler.should_sample(...) by default.

[falenn]

Totally agree - the default setting DEFAULT_OPTIONS = 1 keeps custom-supplied samplers (just as other included samplers) from executing.