Getting "Could not start stream" error on Mac when running sbt - xcode

Question

I am suddenly getting an error when running set on my Mac. I think it started after installing Xcode.
[root] $ run
2015-07-30 19:46 java[651] (FSEvents.framework) FSEventStreamStart:
register_with_server: ERROR: f2d_register_rpc() => (null) (-21)
net.contentobjects.jnotify.macosx.JNotifyException_macosx: Could not
start stream at
net.contentobjects.jnotify.macosx.JNotify_macosx.nativeAddWatch(Native
Method) at
net.contentobjects.jnotify.macosx.JNotify_macosx.addWatch(Unknown
Source) at
net.contentobjects.jnotify.macosx.JNotifyAdapterMacOSX.addWatch(Unknown
Source) at net.contentobjects.jnotify.JNotify.addWatch(Unknown
Source) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native
Method) at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497) at
play.runsupport.JNotifyPlayWatchService$JNotifyDelegate.addWatch(PlayWatchService.scala:140)
at
play.runsupport.JNotifyPlayWatchService$$anonfun$4.apply(PlayWatchService.scala:123)
at
play.runsupport.JNotifyPlayWatchService$$anonfun$4.apply(PlayWatchService.scala:122)
at
scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:244)
at
scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:244)
at scala.collection.immutable.List.foreach(List.scala:318) at
scala.collection.TraversableLike$class.map(TraversableLike.scala:244)
at scala.collection.AbstractTraversable.map(Traversable.scala:105)
at
play.runsupport.JNotifyPlayWatchService.watch(PlayWatchService.scala:122)
at
play.runsupport.PlayWatchService$$anon$1.watch(PlayWatchService.scala:74)
at play.runsupport.Reloader.(Reloader.scala:268) at
play.runsupport.Reloader$.reloader$lzycompute$1(Reloader.scala:174)
at
play.runsupport.Reloader$.play$runsupport$Reloader$$reloader$1(Reloader.scala:174)
at play.runsupport.Reloader$.startDevMode(Reloader.scala:197) at
play.PlayRun$$anonfun$playRunTask$1$$anonfun$apply$2$$anonfun$apply$3.devModeServer$lzycompute$1(PlayRun.scala:75)
at
play.PlayRun$$anonfun$playRunTask$1$$anonfun$apply$2$$anonfun$apply$3.play$PlayRun$class$$anonfun$$anonfun$$anonfun$$devModeServer$1(PlayRun.scala:75)
at
play.PlayRun$$anonfun$playRunTask$1$$anonfun$apply$2$$anonfun$apply$3.apply(PlayRun.scala:98)
at
play.PlayRun$$anonfun$playRunTask$1$$anonfun$apply$2$$anonfun$apply$3.apply(PlayRun.scala:54)
at scala.Function1$$anonfun$compose$1.apply(Function1.scala:47)
Running other commands also throws some errors on screen but works
git status 2015-07-30 19:48 xcodebuild[707] (FSEvents.framework)
FSEventStreamStart: register_with_server: ERROR: f2d_register_rpc() =>
(null) (-21) 2015-07-30 19:48 xcodebuild[707] (FSEvents.framework)
FSEventStreamInvalidate(): failed assertion 'streamRef != NULL'
2015-07-30 19:48 xcodebuild[707] (FSEvents.framework)
FSEventStreamRelease(): failed assertion 'streamRef != NULL'
2015-07-30 19:48:17.915 xcodebuild[707:15323] DVTFilePathFSEvents:
Failed to start fs event stream. On branch devel Your branch is
up-to-date with 'origin/devel'.
I have updated the OS and Xcode to the latest. Any clues on how to fix this?

Answer 1

I've run into this issue recently when using sbt-plugin 2.3.3. There appears to be a problem with fseventsd tracking a large number of files, where file descriptors from the calling process are not always closed properly (probably from spawned child processes)
The solutions would be to upgrade your sbt-plugin version (I've not experienced this issue with versions > 2.3.8 against the latest version of Xcode)
Or to restart fseventsd: sudo killall fseventsd