Add preliminary support for remote debugging.

You can now send a USR1 signal to a bolt or spout to have it pause execution and
allow you to debug it interactively via telnet.  The port should be logged, but
that does not always seem to work for some reason.  For now just use netstat to
find out the port.  The host is always set to 127.0.0.1 for now, but this will
be more flexible in the future.

streamparse/storm/component.py

@@ -1,10 +1,10 @@
 """Base primititve classes for working with Storm."""
 from __future__ import absolute_import, print_function, unicode_literals
 
-import codecs
 import io
 import logging
 import os
+import signal
 import sys
 from collections import deque, namedtuple
 from logging.handlers import RotatingFileHandler
@@ -47,6 +47,19 @@
 log = logging.getLogger(__name__)
 
 
+def remote_pdb_handler(signum, frame):
+    """ Handler to drop us into a remote debugger upon receiving SIGUSR1 """
+    try:
+        from remote_pdb import RemotePdb
+        rdb = RemotePdb(host='127.0.0.1', port=0)
+        rdb.set_trace(frame=frame)
+    except ImportError:
+        log.warning('remote_pdb unavailable.  Please install remote_pdb to '
+                    'allow remote debugging.')
+    # Restore signal handler for later
+    signal.signal(signum, remote_pdb_handler)
+
+
 class StormHandler(logging.Handler):
     """Handler that will send messages back to Storm."""
 
@@ -158,9 +171,10 @@ class Component(object):
     """
 
 
-    def __init__(self, input_stream=sys.stdin, output_stream=sys.stdout):
-        # Ensure we don't fall back on the platform-dependent encoding and always
-        # use UTF-8 https://docs.python.org/3.4/library/sys.html#sys.stdin
+    def __init__(self, input_stream=sys.stdin, output_stream=sys.stdout,
+                 rdb_signal=signal.SIGUSR1):
+        # Ensure we don't fall back on the platform-dependent encoding and
+        # always use UTF-8
         self.input_stream = self._wrap_stream(input_stream)
         self.output_stream = self._wrap_stream(output_stream)
         self.topology_name = None
@@ -177,6 +191,9 @@ def __init__(self, input_stream=sys.stdin, output_stream=sys.stdout):
         self._pending_task_ids = deque()
         self._reader_lock = RLock()
         self._writer_lock = RLock()
+        # Setup remote pdb handler if asked to
+        if rdb_signal is not None:
+            signal.signal(rdb_signal, remote_pdb_handler)
 
     @staticmethod
     def _wrap_stream(stream):