shouldSample(span) {
		if (this.opts.sampling.minPriority != null) {
			if (span.priority < this.opts.sampling.minPriority) return false;
		}

		if (this.rateLimiter) {
			return this.rateLimiter.check();
		}

		if (this.opts.sampling.rate == 0) return false;

		if (this.opts.sampling.rate == 1) return true;

		if (++this.sampleCounter * this.opts.sampling.rate >= 1.0) {
			this.sampleCounter = 0;
			return true;
		}

		return false;
	}
Decide that span should be sampled.

@param {Span} span
@returns {Boolean}
@memberof Tracer