Add a thread dump signal handler

Based on the one in Zuul, but output thread names.  Also, update
Thread constructors to provide useful names.

Change-Id: Ic710a729a1986b7cf67cd7f7812a396a020c4936

nodepool/cmd/nodepoold.py

@@ -26,12 +26,34 @@ import logging.config
 import os
 import sys
 import signal
+import traceback
+import threading
 
 # No nodepool imports here because they pull in paramiko which must not be
 # imported until after the daemonization.
 # https://github.com/paramiko/paramiko/issues/59
 
 
+def stack_dump_handler(signum, frame):
+    signal.signal(signal.SIGUSR2, signal.SIG_IGN)
+    log_str = ""
+    threads = {}
+    for t in threading.enumerate():
+        threads[t.ident] = t
+    for thread_id, stack_frame in sys._current_frames().items():
+        thread = threads.get(thread_id)
+        if thread:
+            thread_name = thread.name
+        else:
+            thread_name = 'Unknown'
+        label = '%s (%s)' % (thread_name, thread_id)
+        log_str += "Thread: %s\n" % label
+        log_str += "".join(traceback.format_stack(stack_frame))
+    log = logging.getLogger("nodepool.stack_dump")
+    log.debug(log_str)
+    signal.signal(signal.SIGUSR2, stack_dump_handler)
+
+
 class NodePoolDaemon(object):
     def __init__(self):
         self.args = None
@@ -74,6 +96,7 @@ class NodePoolDaemon(object):
         self.pool = nodepool.nodepool.NodePool(self.args.config)
 
         signal.signal(signal.SIGUSR1, self.exit_handler)
+        signal.signal(signal.SIGUSR2, stack_dump_handler)
         signal.signal(signal.SIGTERM, self.term_handler)
 
         self.pool.start()

nodepool/fakeprovider.py

@@ -69,7 +69,9 @@ class FakeList(object):
                   metadata={},
                   manager=self)
         self._list.append(s)
-        t = threading.Thread(target=self._finish, args=(s, 0.5, 'ACTIVE'))
+        t = threading.Thread(target=self._finish,
+                             name='FakeProvider create',
+                             args=(s, 0.5, 'ACTIVE'))
         t.start()
         return s
 

nodepool/nodepool.py

@@ -52,7 +52,8 @@ class NodeCompleteThread(threading.Thread):
     log = logging.getLogger("nodepool.NodeCompleteThread")
 
     def __init__(self, nodepool, nodename, jobname, result):
-        threading.Thread.__init__(self)
+        threading.Thread.__init__(self, name='NodeCompleteThread for %s' %
+                                  nodename)
         self.nodename = nodename
         self.nodepool = nodepool
         self.jobname = jobname
@@ -104,7 +105,7 @@ class NodeUpdateListener(threading.Thread):
     log = logging.getLogger("nodepool.NodeUpdateListener")
 
     def __init__(self, nodepool, addr):
-        threading.Thread.__init__(self)
+        threading.Thread.__init__(self, name='NodeUpdateListener')
         self.nodepool = nodepool
         self.socket = self.nodepool.zmq_context.socket(zmq.SUB)
         event_filter = b""
@@ -218,7 +219,7 @@ class NodeLauncher(threading.Thread):
     log = logging.getLogger("nodepool.NodeLauncher")
 
     def __init__(self, nodepool, provider, image, target, node_id, timeout):
-        threading.Thread.__init__(self)
+        threading.Thread.__init__(self, name='NodeLauncher for %s' % node_id)
         self.provider = provider
         self.image = image
         self.target = target
@@ -352,7 +353,8 @@ class ImageUpdater(threading.Thread):
     log = logging.getLogger("nodepool.ImageUpdater")
 
     def __init__(self, nodepool, provider, image, snap_image_id):
-        threading.Thread.__init__(self)
+        threading.Thread.__init__(self, name='ImageUpdater for %s' %
+                                  snap_image_id)
         self.provider = provider
         self.image = image
         self.snap_image_id = snap_image_id
@@ -543,7 +545,7 @@ class NodePool(threading.Thread):
     log = logging.getLogger("nodepool.NodePool")
 
     def __init__(self, configfile):
-        threading.Thread.__init__(self)
+        threading.Thread.__init__(self, name='NodePool')
         self.configfile = configfile
         self._stopped = False
         self.config = None

nodepool/task_manager.py

@@ -57,7 +57,7 @@ class TaskManager(threading.Thread):
     log = logging.getLogger("nodepool.ProviderManager")
 
     def __init__(self, client, name, rate):
-        super(TaskManager, self).__init__()
+        super(TaskManager, self).__init__(name=name)
         self.daemon = True
         self.queue = Queue.Queue()
         self._running = True