Add a thread-dumping handler

Add a 'crier' handler to dump the thread stacks of running threads to
the log, for easier debugging.

headphones/crier.py

@@ -0,0 +1,36 @@
+import pprint
+import sys
+import threading
+import traceback
+
+from headphones import logger
+
+
+def cry():
+    """
+    Logs thread traces.
+    """
+    tmap = {}
+    main_thread = None
+    # get a map of threads by their ID so we can print their names
+    # during the traceback dump
+    for t in threading.enumerate():
+        if t.ident:
+            tmap[t.ident] = t
+        else:
+            main_thread = t
+
+    # Loop over each thread's current frame, writing info about it
+    for tid, frame in sys._current_frames().iteritems():
+        thread = tmap.get(tid, main_thread)
+
+        lines = []
+        lines.append('%s\n' % thread.getName())
+        lines.append('========================================\n')
+        lines += traceback.format_stack(frame)
+        lines.append('========================================\n')
+        lines.append('LOCAL VARIABLES:\n')
+        lines.append('========================================\n')
+        lines.append(pprint.pformat(frame.f_locals))
+        lines.append('\n\n')
+        logger.info("".join(lines))

headphones/webserve.py

@@ -28,7 +28,7 @@ import urllib2
 
 import os
 import re
-from headphones import logger, searcher, db, importer, mb, lastfm, librarysync, helpers, notifiers
+from headphones import logger, searcher, db, importer, mb, lastfm, librarysync, helpers, notifiers, crier
 from headphones.helpers import checked, radio, today, clean_name
 from mako.lookup import TemplateLookup
 from mako import exceptions
@@ -69,6 +69,11 @@ class WebInterface(object):
         artists = myDB.select('SELECT * from artists order by ArtistSortName COLLATE NOCASE')
         return serve_template(templatename="index.html", title="Home", artists=artists)
 
+    @cherrypy.expose
+    def threads(self):
+        crier.cry()
+        raise cherrypy.HTTPRedirect("home")
+
     @cherrypy.expose
     def artistPage(self, ArtistID):
         myDB = db.DBConnection()