core: use $DEBUG variable to enable debugging

lib/gruvi/endpoints.py

@@ -22,9 +22,12 @@
 from .ssl import SslTransport
 from .sslcompat import create_default_context
 from .address import getaddrinfo, saddr
+from .util import EnvBool
 
 __all__ = ['create_connection', 'create_server', 'Endpoint', 'Client', 'Server']
 
+DEBUG = EnvBool.new('DEBUG')
+
 
 @switchpoint
 def create_connection(protocol_factory, address, ssl=False, server_hostname=None,
@@ -340,7 +343,7 @@ def handle_connection(self, client, ssl):
             transport = Transport(client)
         transport._log = self._log
         transport._server = self
-        if __debug__:
+        if DEBUG:
             self._log.debug('new connection on {}', saddr(client.getsockname()))
             if hasattr(client, 'getpeername'):
                 self._log.debug('remote peer is {}', saddr(client.getpeername()))

lib/gruvi/util.py

@@ -8,6 +8,7 @@
 
 from __future__ import absolute_import, print_function
 
+import os
 import sys
 import re
 import functools
@@ -17,6 +18,29 @@
 __all__ = []
 
 
+class EnvBool(object):
+    """A boolean-like object that takes its value from the environment variable
+    *name*."""
+
+    _zero_values = ('0', 'n', 'f', 'false')
+
+    def __init__(self, name):
+        self._name = name
+
+    @classmethod
+    def new(cls, name):
+        # Optimize away $DEBUG when interpreter is running with -O
+        if name == 'DEBUG' and not __debug__:
+            return False
+        return cls(name)
+
+    def __nonzero__(self):
+        value = os.environ.get(self._name, '0')
+        return value.lower() not in self._zero_values
+
+    __bool__ = __nonzero__
+
+
 class AbsentType(object):
     """A type that represents the absence of a value.