feat: Add environment variables to override common options, closes #498

Author: jpmckinney

docs/config.rst

@@ -12,9 +12,16 @@ them in order with the latest one taking more priority:
 * ``scrapyd.conf``
 * ``~/.scrapyd.conf`` (users home directory)
 
-The configuration file supports the following options (see default values in
+The configuration file supports the options below (see default values in
 the :ref:`example <config-example>`).
 
+The following environment variables override corresponding options:
+
+* ``SCRAPYD_HTTP_PORT`` (``http_port``)
+* ``SCRAPYD_BIND_ADDRESS`` (``bind_address``)
+* ``SCRAPYD_USERNAME`` (``username``)
+* ``SCRAPYD_PASSWORD`` (``password``)
+
 http_port
 ---------
 

docs/news.rst

@@ -8,6 +8,11 @@ Release notes
 Unreleased
 ----------
 
+Added
+~~~~~
+
+- Add environment variables to override common options. See :doc:`config`.
+
 Changed
 ~~~~~~~
 

scrapyd/app.py

@@ -1,3 +1,4 @@
+import os
 import sys
 
 from scrapy.utils.misc import load_object
@@ -16,8 +17,8 @@
 
 
 def create_wrapped_resource(webcls, config, app):
-    username = config.get('username', '')
-    password = config.get('password', '')
+    username = os.getenv('SCRAPYD_USERNAME') or config.get('username', '')
+    password = os.getenv('SCRAPYD_PASSWORD') or config.get('password', '')
     if ':' in username:
         sys.exit("The `username` option contains illegal character ':', "
                  "check and update the configuration file of Scrapyd")
@@ -35,8 +36,8 @@ def create_wrapped_resource(webcls, config, app):
 
 def application(config):
     app = Application("Scrapyd")
-    http_port = config.getint('http_port', 6800)
-    bind_address = config.get('bind_address', '127.0.0.1')
+    http_port = int(os.getenv('SCRAPYD_HTTP_PORT') or config.getint('http_port', 6800))
+    bind_address = os.getenv('SCRAPYD_BIND_ADDRESS') or config.get('bind_address', '127.0.0.1')
     poll_interval = config.getfloat('poll_interval', 5)
 
     poller = QueuePoller(config)