Merge pull request #4210 from alphagov/paas-redis-migration-181796569

Prepare to switch to Redis on PaaS

app/cloudfoundry_config.py

@@ -8,6 +8,12 @@ import os
 
 
 def extract_cloudfoundry_config():
+    vcap_services = json.loads(os.environ['VCAP_SERVICES'])
+
+    # Redis config
+    if 'redis' in vcap_services:
+        os.environ['REDIS_URL'] = vcap_services['redis'][0]['credentials']['uri']
+
     vcap_application = json.loads(os.environ.get('VCAP_APPLICATION'))
     os.environ['NOTIFY_ENVIRONMENT'] = vcap_application['space_name']
     os.environ['NOTIFY_LOG_PATH'] = '/home/vcap/logs/app.log'

gunicorn_config.py

@@ -1,6 +1,8 @@
 import os
 import sys
 import traceback
+import eventlet
+import socket
 
 import gunicorn
 from gds_metrics.gunicorn import child_exit  # noqa
@@ -17,3 +19,21 @@ def worker_abort(worker):
     worker.log.info("worker received ABORT")
     for stack in sys._current_frames().values():
         worker.log.error(''.join(traceback.format_stack(stack)))
+
+
+def fix_ssl_monkeypatching():
+    """
+    eventlet works by monkey-patching core IO libraries (such as ssl) to be non-blocking. However, there's currently
+    a bug: In the normal socket library it may throw a timeout error as a `socket.timeout` exception. However
+    eventlet.green.ssl's patch raises an ssl.SSLError('timed out',) instead. redispy handles socket.timeout but not
+    ssl.SSLError, so we solve this by monkey patching the monkey patching code to raise the correct exception type
+    :scream:
+    https://github.com/eventlet/eventlet/issues/692
+    """
+    # this has probably already been called somewhere in gunicorn internals, however, to be sure, we invoke it again.
+    # eventlet.monkey_patch can be called multiple times without issue
+    eventlet.monkey_patch()
+    eventlet.green.ssl.timeout_exc = socket.timeout
+
+
+fix_ssl_monkeypatching()

tests/app/test_cloudfoundry_config.py

@@ -1,3 +1,4 @@
+import json
 import os
 
 import pytest
@@ -6,12 +7,33 @@ from app.cloudfoundry_config import extract_cloudfoundry_config
 
 
 @pytest.fixture
-def cloudfoundry_environ(os_environ):
+def cloudfoundry_config():
+    return {
+        'redis': [{
+            'credentials': {
+                'uri': 'redis uri'
+            }
+        }],
+    }
+
+
+@pytest.fixture
+def vcap_application(os_environ):
     os.environ['VCAP_APPLICATION'] = '{"space_name":"🚀🌌"}'
 
 
-def test_extract_cloudfoundry_config_populates_other_vars(cloudfoundry_environ):
+def test_extract_cloudfoundry_config_populates_other_vars(vcap_application, cloudfoundry_config):
+    os.environ['VCAP_SERVICES'] = json.dumps(cloudfoundry_config)
     extract_cloudfoundry_config()
 
+    assert os.environ['REDIS_URL'] == 'redis uri'
     assert os.environ['NOTIFY_ENVIRONMENT'] == '🚀🌌'
     assert os.environ['NOTIFY_LOG_PATH'] == '/home/vcap/logs/app.log'
+
+
+def test_set_config_env_vars_copes_if_redis_not_set(vcap_application, cloudfoundry_config):
+    del cloudfoundry_config['redis']
+    os.environ['VCAP_SERVICES'] = json.dumps(cloudfoundry_config)
+
+    extract_cloudfoundry_config()
+    assert 'REDIS_URL' not in os.environ