private boolean shouldSampleByDefault(int sample, int duration) {
        return isOverDefaultSlowThreshold(duration) || withinDefaultRateRange(sample);
    }
When 'duration' is over 'default trace segment's slow threshold' that should be sampled. Or when 'sample' is with
in [0,defaultSamplingRate) that also should be sampled.

@param sample   sample rate of trace segment
@param duration duration of trace segment
@return
oap-server/analyzer/agent-analyzer/src/main/java/org/apache/skywalking/oap/server/analyzer/provider/trace/TraceSamplingPolicyWatcher.java