public LoggingServiceBuilder sampler(Sampler<? super ServiceRequestContext> sampler) {
        requireNonNull(sampler, "sampler");
        successSampler = sampler;
        failureSampler = sampler;
        return this;
    }
Sets the {@link Sampler} that determines which request needs logging.
This method sets both success and failure sampler.
Use {@link #successSampler(Sampler)} and {@link #failureSampler(Sampler)}
if you want to specify a different sampler for each case.
core/src/main/java/com/linecorp/armeria/server/logging/LoggingServiceBuilder.java