fix: prefer the LogBeginner observer entry point

otherwise its buffer pointlessly keeps around 65k old log message
events for replaying

fixes #786

autopush/logging.py

@@ -8,6 +8,7 @@
 import sys
 import time
 import threading
+from typing import Any  # noqa
 
 import boto3
 import raven
@@ -17,6 +18,7 @@
 from twisted.logger import (
     formatEvent,
     formatEventAsClassicLogText,
+    globalLogBeginner,
     globalLogPublisher,
     LogLevel,
     ILogObserver
@@ -53,6 +55,25 @@
 ])
 
 
+# whether the global LogBeginner.beginLoggingTo has been called: it
+# should only be called once
+began_logging = False
+
+
+def begin_or_register(observer):
+    """Register observer with the global LogPublisher
+
+    Registers via the global LogBeginner the first time called.
+    """
+    # type: (Any) -> None
+    global began_logging
+    if not began_logging:
+        globalLogBeginner.beginLoggingTo([observer], redirectStandardIO=False)
+        began_logging = True
+    else:
+        globalLogPublisher.addObserver(observer)
+
+
 @implementer(ILogObserver)
 class PushLogger(object):
     """Twisted LogObserver implementation
@@ -182,7 +203,7 @@ def start(self):
             self._output = io.open(self._filename, "a", encoding="utf-8")
         if self.firehose:
             self.firehose.start()
-        globalLogPublisher.addObserver(self)
+        begin_or_register(self)
 
     def stop(self):
         globalLogPublisher.removeObserver(self)

autopush/tests/test_integration.py

@@ -45,6 +45,7 @@
     get_month,
     has_connected_this_month
 )
+from autopush.logging import begin_or_register
 from autopush.main import endpoint_paths
 from autopush.settings import AutopushSettings
 from autopush.utils import base64url_encode
@@ -372,7 +373,7 @@ def setUp(self):
         )
 
         self.logs = TestingLogObserver()
-        globalLogPublisher.addObserver(self.logs)
+        begin_or_register(self.logs)
 
         router_table = os.environ.get("ROUTER_TABLE", "router_int_test")
         storage_table = os.environ.get("STORAGE_TABLE", "storage_int_test")