Hi there,

We just upgrade to ROS melodic from kinetic recently, and found that node connections take too long to establish, sometimes even over 2 seconds.
Our application is very time sensitive, and this affects a lot.

After some debug, I found that the issue is caused by countFreeFDs() function in xmlrpcpp.

It's comments say:

int XmlRpcServer::countFreeFDs() {
  // NOTE(austin): this function is not free, but in a few small tests it only
  // takes about 1.2mS when querying 50k file descriptors.

But inside docker container, file descriptors number usually is 1048576:

$ python -c "import resource; print(resource.getrlimit(resource.RLIMIT_NOFILE))"
(1048576, 1048576)

that takes a huge time to query.

docker version we are using is

$ docker --version
Docker version 19.03.5, build 633a0ea838

Any idea how to fix this? Thanks