# 
# 
# add_file "genproxy.py"
#  content [408f46a3f5fe0d792eb62e92a8faaf5c28c67a54]
# 
# patch "common.py"
#  from [3f13b48c9393d3d7b2cf98e6c41fb750f6980f12]
#    to [6b2e20c94f126e5c42ff25f9c953c96883d5d87f]
# 
# patch "mtn.py"
#  from [5974c2d53154febf368c5d2435dd84c6e23d819a]
#    to [129ee303fd073267a567dcf79c20517f3590c856]
# 
#   set "genproxy.py"
#  attr "mtn:execute"
# value "true"
# 
============================================================
--- genproxy.py	408f46a3f5fe0d792eb62e92a8faaf5c28c67a54
+++ genproxy.py	408f46a3f5fe0d792eb62e92a8faaf5c28c67a54
@@ -0,0 +1,25 @@
+#!/usr/bin/env python
+
+class GeneratorProxy(object):
+    def __init__(self, generator):
+        self.generator = generator
+    def __iter__(self):
+        return self
+    def next(self):
+        return self.generator.next()
+
+class Seedy(GeneratorProxy):
+    def __del__(self):
+        print "testing"
+        
+def test():
+    yield 2
+    yield 3
+    yield 4
+
+if __name__ == '__main__':
+    a = test()
+    b = Seedy(test())
+    for i in b:
+        print i
+    
============================================================
--- common.py	3f13b48c9393d3d7b2cf98e6c41fb750f6980f12
+++ common.py	6b2e20c94f126e5c42ff25f9c953c96883d5d87f
@@ -1,9 +1,10 @@ from web import debug
 
 import datetime
 import time
 import fcntl
 import os
 from web import debug
+import traceback
 
 def parse_timecert(value):
     return apply(datetime.datetime, time.strptime(value, "%Y-%m-%dT%H:%M:%S")[:6])
@@ -23,7 +24,7 @@ def terminate_popen3(process):
                 os.kill(process.pid, signal.SIGKILL)
             process.wait()
         except:
-            debug("%s failed_to_stop %s" % (os.getpid(), process.pid))
+            debug("%s failed_to_stop %s (%s)" % (os.getpid(), process.pid, traceback.format_exc()))
 
 def ago(event):
     def plural(v, singular, plural):
============================================================
--- mtn.py	5974c2d53154febf368c5d2435dd84c6e23d819a
+++ mtn.py	129ee303fd073267a567dcf79c20517f3590c856
@@ -8,6 +8,7 @@ from traceback import format_exc
 import popen2
 from common import set_nonblocking, terminate_popen3
 from traceback import format_exc
+import genproxy
 
 import web
 from web import debug
@@ -60,6 +61,7 @@ class Automate(Runner):
        """
     def __init__(self, *args, **kwargs):
         Runner.__init__(*[self] + list(args), **kwargs)
+        debug("** a new automate instance just started **")
         self.lock = threading.Lock()
         self.process = None
 
@@ -80,14 +82,44 @@ class Automate(Runner):
 
     def run(self, *args, **kwargs):
 #        debug(("automate is running:", args, kwargs))
-        if not self.lock.acquire(False):
-            raise MonotoneException("Automate process can't be called: it is already locked.")
-        try:
-            rv = apply(self.__run, args, kwargs)
-        finally:
-            self.lock.release()
-        return rv
 
+        lock = self.lock
+        stop = self.stop
+        class CleanRequest(genproxy.GeneratorProxy):
+            def __init__(self, *args, **kwargs):
+                genproxy.GeneratorProxy.__init__(self, *args, **kwargs)
+
+                # nb; this used to be False, but True seems to behave more sensibly.
+                # in particular, if someone holds down Refresh sometimes the code 
+                # gets here before __del__ is called on the previous iterator, 
+                # causing a pointless error to occur
+                if not lock.acquire(True):
+                    # I've checked; this exception does _not_ cause __del__ to run, so 
+                    # we don't accidentally unlock a lock below
+                    raise MonotoneException("Automate request cannot be called: it is already locked! This indicates a logic error in ViewMTN; please report.")
+
+            def __del__(self):
+                def read_any_unread_output():
+                    try:
+                        # this'll raise StopIteration if we're done
+                        self.next()
+                        # okay, we're not done..
+                        debug("warning: Automate output not completely read; reading manually.")
+                        for stanza in self:
+                            pass
+                    except StopIteration:
+                        debug("got a StopIteration ok.")
+                        pass
+
+                try:
+                    read_any_unread_output()
+                    lock.release()
+                except:
+                    debug("exception cleaning up after Automation; calling stop()!")
+                    stop()
+
+        return CleanRequest(self.__run(*args, **kwargs))
+
     def __run(self, command, args):
         enc = "l%d:%s" % (len(command), command)
         enc += ''.join(map(lambda x: "%d:%s" % (len(x), x), args)) + 'e'
@@ -303,9 +335,13 @@ class Operations:
         
 class Operations:
     def __init__(self, runner_args):
+        debug ("** a new Operations just started **")
         self.standalone = apply(Standalone, runner_args)
         self.automate = apply(Automate, runner_args)
 
+    def __del__(self):
+        debug ( "** DESTROY operations")
+
     def tags(self):
         for stanza in basic_io_from_stream(self.automate.run('tags', [])):
             if stanza[0] == 'tag':