manage.py: Save an extra Django startup by converting one script to a library.

This saves us from spending 200-250ms of CPU time importing Django
again just to log that we're running a management command.  On
`scripts/restart-server`, this saves us from one thundering herd of
Django startups when all the queue workers are restarted; but there's
still the Django startup for the `manage.py` process itself for each
worker, so on a machine with e.g. 2 (virtual) cores the restart is
still painful.

manage.py

@@ -4,8 +4,6 @@ from __future__ import print_function
 
 import os
 import sys
-import logging
-import subprocess
 
 BASE_DIR = os.path.dirname(os.path.abspath(__file__))
 sys.path.append(BASE_DIR)
@@ -20,10 +18,9 @@ if __name__ == "__main__":
 
     from django.conf import settings
     from django.core.management.base import CommandError
+    from scripts.lib.zulip_tools import log_management_command
 
-    logger = logging.getLogger("zulip.management")
-    subprocess.check_call([os.path.join(BASE_DIR, "scripts", "lib", "log-management-command"),
-                           " ".join(sys.argv)])
+    log_management_command(" ".join(sys.argv), settings.MANAGEMENT_LOG_PATH)
 
     if "--no-traceback" not in sys.argv and len(sys.argv) > 1:
         sys.argv.append("--traceback")

scripts/lib/log-management-command

@@ -1,25 +0,0 @@
-#!/usr/bin/env python3
-import sys
-import logging
-import os
-from os.path import dirname, abspath
-
-BASE_DIR = dirname(dirname(dirname(abspath(__file__))))
-sys.path.append(BASE_DIR)
-import scripts.lib.setup_path_on_import
-
-os.environ.setdefault("DJANGO_SETTINGS_MODULE", "zproject.settings")
-from django.conf import settings
-
-logger = logging.getLogger("zulip.management")
-if not os.path.exists(settings.MANAGEMENT_LOG_PATH):
-    dir = os.path.dirname(settings.MANAGEMENT_LOG_PATH)
-    if not os.path.exists(dir):
-        os.makedirs(dir)
-
-file_handler = logging.FileHandler(settings.MANAGEMENT_LOG_PATH)
-formatter = logging.Formatter("%(asctime)s: %(message)s")
-file_handler.setFormatter(formatter)
-logger.addHandler(file_handler)
-logger.setLevel(logging.INFO)
-logger.info("Ran '%s'" % (sys.argv[1],))

scripts/lib/zulip_tools.py

@@ -2,6 +2,7 @@
 from __future__ import print_function
 import datetime
 import errno
+import logging
 import os
 import pwd
 import re
@@ -11,7 +12,7 @@ import sys
 import time
 
 if False:
-    from typing import Sequence, Any
+    from typing import Sequence, Text, Any
 
 DEPLOYMENTS_DIR = "/home/zulip/deployments"
 LOCK_DIR = os.path.join(DEPLOYMENTS_DIR, "lock")
@@ -131,3 +132,18 @@ def run(args, **kwargs):
               ENDC)
         print()
         raise
+
+def log_management_command(cmd, log_path):
+    # type: (Text, Text) -> None
+    log_dir = os.path.dirname(log_path)
+    if not os.path.exists(log_dir):
+        os.makedirs(log_dir)
+
+    formatter = logging.Formatter("%(asctime)s: %(message)s")
+    file_handler = logging.FileHandler(log_path)
+    file_handler.setFormatter(formatter)
+    logger = logging.getLogger("zulip.management")
+    logger.addHandler(file_handler)
+    logger.setLevel(logging.INFO)
+
+    logger.info("Ran '%s'" % (cmd,))