presto-main/src/main/java/io/prestosql/server/GenerateTraceTokenRequestFilter.java/GenerateTraceTokenRequestFilter/filterRequest
class GenerateTraceTokenRequestFilter:    @Override
    public Request filterRequest(Request request)
    {
        requireNonNull(request, "request is null");
        String newToken = createToken(sequence.getAndIncrement());
        return fromRequest(request)
                .setHeader(TRACETOKEN_HEADER, newToken)
                .build();
    }