[launchd-dev] correctly running service still getting 'Service only ran for 0 seconds.' log entries

Hello, I put http://paste.scsys.co.uk/483275 at /Library/LaunchDaemons/homebrew.mxcl.httpd24.plist and it started apache, but Server.app keeps logging 'com.apple.xpc.launchd[1] (homebrew.mxcl.httpd24): Service only ran for 0 seconds. Pushing respawn out by 10 seconds.' Why is launchd trying to restart its target when it is already running? Thanks!