I use my macs for development. That means that there's a lot of things running and I usually have a lot of heavy apps open. So I quite often hit the error "Too many open files". On linux - this is fixed using sysctl - but on later OSX/macOS it is done using launchd. Earlier OSX versions could use a /etc/launchd.conf file - but - for the latest versions I've found that this post from basho docs for riak works fine.

In short - create two files

/Library/LaunchDaemons/limit.maxfiles.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
  <dict>
    <key>Label</key>
    <string>limit.maxfiles</string>
    <key>ProgramArguments</key>
    <array>
      <string>launchctl</string>
      <string>limit</string>
      <string>maxfiles</string>
      <string>200000</string>
      <string>200000</string>
    </array>
    <key>RunAtLoad</key>
    <true/>
    <key>ServiceIPC</key>
    <false/>
  </dict>
</plist>

/Library/LaunchDaemons/limit.maxproc.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple/DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
  <dict>
    <key>Label</key>
    <string>limit.maxproc</string>
    <key>ProgramArguments</key>
    <array>
      <string>launchctl</string>
      <string>limit</string>
      <string>maxproc</string>
      <string>2048</string>
      <string>2048</string>
    </array>
    <key>RunAtLoad</key>
    <true />
    <key>ServiceIPC</key>
      <false />
  </dict>
</plist>

Make sure both are owned root:wheel and have permissions -rw-r--r-- and then either restart or reload the launchd config.

ulimit -n and ulimit -u can be used to test the results afterwards.