static void maybeLog(String prefix, ServiceRequestContext ctx, AggregatedHttpRequest request) {
    if (!LOGGER.isDebugEnabled()) return;
    LOGGER.debug("{} sent by clientAddress->{}, userAgent->{}",
      prefix, ctx.clientAddress(), request.headers().get(HttpHeaderNames.USER_AGENT)
    );
  }
This synchronously decodes the message so that users can see data errors.
zipkin-server/src/main/java/zipkin2/server/internal/ZipkinHttpCollector.java