Hot reloading uses native file watching features of unix-compatible systems. This is extremely handy and efficient, but unfortunately most systems have very low limits on watched and open files. If you use hot reloading a lot, you should expect to see:
Error: watch EMFILE or similar.
To solve the problem you need to raise your filesystem limits. This may be a two-step process. On Linux, there’re hard limits (something root user can change in /etc/limits.conf or /ets/security/limits.conf) that govern the limits individual users can alter from command-line.
You should probably put
ulimit -n 10000in your .profile file, because it does not persist between restarts.
For OS-X and Solaris-specific instructions see a Stackoverflow Answer