Tracer emits although using `AlwaysOffSampler`

I’d expect that using AlwaysOffSampler the tracer is silent, but it in fact spams the console. Here is a minimal example:

from opencensus.trace import tracer as tracer_module
from opencensus.trace.samplers import AlwaysOffSampler

tracer = tracer_module.Tracer(sampler=AlwaysOffSampler())

with tracer.span(name='should-not-trace') as span:
    pass

It prints:

[SpanData(name='should-not-trace', context=<opencensus.trace.span_context.SpanContext object at 0x7ff7ac107978>, span_id='4ac72045f7064ac2', parent_span_id=None, attributes={}, start_time='2018-11-22T08:42:32.096948Z', end_time='2018-11-22T08:42:32.096951Z', child_span_count=0, stack_trace=None, time_events=[], links=[], status=None, same_process_as_parent_span=None, span_kind=0)]

Doc-string of AlwaysOffSampler says “Do not trace any requests”. This is not what I’d expect then.

If for any reason this is the intended behavior, please suggest how I can turn tracing off completely. Thanks!

EDIT: I am on Python 3 with opencensus 0.1.5

[liyanhui1228]

Yep will add that to readme! I’ll go ahead to close this issue and feel free to reopen if you find anything else.

[cbpygit]

Thank you very much @liyanhui1228, this helps a lot. I guess it would be sufficient if you add this on/off switching somewhere in the Readme. Should be quite regularly needed to e.g. define an environment variable that allows for easy on/off of tracing.