Calendar Server crashes in Yosemite 10.10 with Server App 4.0

Question

I am running an OS X Server (4.0) in Yosemite 10.10 locally on my iMac to provide calendars in our house. Since the combined update of OS and the "Server App" the calendar server crashes frequently. It restarts when I run the server app but crashes again a couple of minutes later.
Error log is below, I hope someone has an idea.
Thanks,
  shoot_me
2014-10-22 21:34:15+0200 [-] Exception from execute() on first statement in transaction.  Possibly caused by a database server restart.  Automatically reconnecting now.
  Traceback (most recent call last):
   File "/Applications/Server.app/Contents/ServerRoot/Library/CalendarServer/lib/python 2.7/site-packages/twext/internet/threadutils.py", line 48, in _run
     while self._qpull():
   File "/Applications/Server.app/Contents/ServerRoot/Library/CalendarServer/lib/python 2.7/site-packages/twext/internet/threadutils.py", line 68, in _qpull
     self._oneWorkUnit(*work)
   File "/Applications/Server.app/Contents/ServerRoot/Library/CalendarServer/lib/python 2.7/site-packages/twext/internet/threadutils.py", line 74, in _oneWorkUnit
     result = instruction()
   File "/Applications/Server.app/Contents/ServerRoot/Library/CalendarServer/lib/python 2.7/site-packages/twext/enterprise/adbapi2.py", line 312, in <lambda>
     lambda: self._reallyExecSQL(*args, **kw)
  --- <exception caught here> ---
   File "/Applications/Server.app/Contents/ServerRoot/Library/CalendarServer/lib/python 2.7/site-packages/twext/enterprise/adbapi2.py", line 242, in _reallyExecSQL
     self._cursor.execute(sql, args)
   File "/Applications/Server.app/Contents/ServerRoot/Library/CalendarServer/lib/python 2.7/site-packages/txdav/base/datastore/dbapiclient.py", line 77, in execute
     self.realCursor.execute(sql, args)
   File "/Applications/Server.app/Contents/ServerRoot/Library/CalendarServer/lib/python 2.7/site-packages/pgdb.py", line 323, in execute
     return self.executemany(operation, [params])
   File "/Applications/Server.app/Contents/ServerRoot/Library/CalendarServer/lib/python 2.7/site-packages/pgdb.py", line 342, in executemany
     raise _op_error("can't start transaction")
  pg.OperationalError: can't start transaction
2014-10-22 21:34:15+0200 [-] [twext.enterprise.jobqueue#error] Failed to pick a new job, FATAL:  the database system is shutting down
2014-10-22 21:34:15+0200 [-] Unhandled Error
  Traceback (most recent call last):
   File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/twi sted/python/context.py", line 81, in callWithContext
     return func(*args,**kw)
   File "/Applications/Server.app/Contents/ServerRoot/Library/CalendarServer/lib/python 2.7/site-packages/twext/internet/threadutils.py", line 48, in _run
     while self._qpull():
   File "/Applications/Server.app/Contents/ServerRoot/Library/CalendarServer/lib/python 2.7/site-packages/twext/internet/threadutils.py", line 69, in _qpull
     return True
   File "/Applications/Server.app/Contents/ServerRoot/Library/CalendarServer/lib/python 2.7/site-packages/twext/internet/threadutils.py", line 82, in _oneWorkUnit
     self._reactor.callFromThread(deferred.callback, result)
  --- <exception caught here> ---
   File "/Applications/Server.app/Contents/ServerRoot/Library/CalendarServer/lib/python 2.7/site-packages/twext/internet/threadutils.py", line 74, in _oneWorkUnit
     result = instruction()
   File "/Applications/Server.app/Contents/ServerRoot/Library/CalendarServer/lib/python 2.7/site-packages/twext/enterprise/adbapi2.py", line 352, in reallySomething
     really()
   File "/Applications/Server.app/Contents/ServerRoot/Library/CalendarServer/lib/python 2.7/site-packages/txdav/base/datastore/dbapiclient.py", line 176, in rollback
     self.realConnection.rollback()
   File "/Applications/Server.app/Contents/ServerRoot/Library/CalendarServer/lib/python 2.7/site-packages/pgdb.py", line 521, in rollback
     raise _op_error("connection has been closed")
  pg.OperationalError: connection has been closed

Answer 1

Looks like a corrupt database. I suggest you export all calendars on the clients, then delete /Library/Server/Wiki/Data and reinitialize the server.
Back up all data.
Quit the Server application and drag it to the Trash, but don't empty. You'll be prompted to confirm that you want to stop all services. You won't lose any data.
If you're using the server for DNS, temporarily change the primary DNS setting in the Network preference pane to your ISP's DNS.
Put the app back where it was and launch it. Test.
Revert the DNS setting, if applicable.