Occasionally IcePush throws following exceptions:

Caused by: java.util.ConcurrentModificationException
         at java.util.HashMap$HashIterator.nextEntry(HashMap.java:977)
         at java.util.HashMap$ValueIterator.next(HashMap.java:1006)
         at java.util.AbstractCollection.toArray(AbstractCollection.java:124)
         at java.util.ArrayList.<init>(ArrayList.java:131)
         at org.icepush.servlet.BrowserDispatcher.discardUnusedServlets(BrowserDispatcher.java:89)
         at org.icepush.servlet.BrowserDispatcher.service(BrowserDispatcher.java:47)
         at org.icepush.servlet.PathDispatcher.service(PathDispatcher.java:45)
         at org.icepush.servlet.MainServlet.service(MainServlet.java:71)

Discarding unused servlets should be thread-safe. This looks to be tightly linked to issue PUSH-151. This exception is thrown from exactly the same line as exception described in issue PUSH-151.