health: Fail health check if specific file is present.

This lets us mark a server dead in the load balancer.

r2/r2/controllers/error.py

@@ -147,7 +147,9 @@ class ErrorController(RedditController):
         return template.render(logo_url=static(g.default_header_url))
 
     def send503(self):
-        response.headers["Retry-After"] = str(request.environ["retry_after"])
+        retry_after = request.environ.get("retry_after")
+        if retry_after:
+            response.headers["Retry-After"] = str(retry_after)
         return request.environ['usable_error_content']
 
     def GET_document(self):

r2/r2/controllers/health.py

@@ -21,8 +21,10 @@
 ###############################################################################
 
 import json
+import os
 
-from pylons import g, response
+from pylons import g, request, response
+from pylons.controllers.util import abort
 
 from r2.controllers.reddit_base import MinimalController
 from r2.lib import promote
@@ -39,6 +41,10 @@ class HealthController(MinimalController):
         pass
 
     def GET_health(self):
+        if os.path.exists("/var/opt/reddit/quiesce"):
+            request.environ["usable_error_content"] = "No thanks, I'm full."
+            abort(503)
+
         response.content_type = "application/json"
         return json.dumps(g.versions, sort_keys=True, indent=4)