From a9d35e09e4eddb14ea4709272b9ab84f4cce6e56 Mon Sep 17 00:00:00 2001
From: Henning Jacobs <henning@jacobs1.de>
Date: Fri, 6 Jan 2017 23:29:02 +0100
Subject: [PATCH] #49 redis backend for pub/sub

---
 app.py           | 62 ++++++++++++++++++++++++++++++++++--------------
 requirements.txt |  1 +
 2 files changed, 45 insertions(+), 18 deletions(-)

diff --git a/app.py b/app.py
index 9da251e..5f97c41 100755
--- a/app.py
+++ b/app.py
@@ -14,9 +14,11 @@ import os
 import re
 import requests
 import datetime
+import redis
 import time
 import tokens
 from queue import Queue
+from redlock import Redlock
 
 from flask import Flask, redirect
 from flask_oauthlib.client import OAuth, OAuthRemoteApp
@@ -29,9 +31,9 @@ class MemoryStore:
 
     def acquire_lock(self):
         # no-op for memory store
-        pass
+        return 'fake-lock'
 
-    def release_lock(self):
+    def release_lock(self, lock):
         # no op for memory store
         pass
 
@@ -50,7 +52,28 @@ class MemoryStore:
             self._queues.remove(queue)
 
 
-STORE = MemoryStore()
+class RedisStore:
+    def __init__(self, url):
+        self._url = url
+        self._redis = redis.StrictRedis.from_url(url)
+        self._redlock = Redlock([url])
+
+    def acquire_lock(self):
+        return self._redlock.lock('update', 10000)
+
+    def release_lock(self, lock):
+        self._redlock.unlock(lock)
+
+    def publish(self, event_type, event_data):
+        self._redis.publish('default', '{}:{}'.format(event_type, json.dumps(event_data, separators=(',', ':'))))
+
+    def listen(self):
+        p = self._redis.pubsub()
+        p.subscribe('default')
+        for message in p.listen():
+            if message['type'] == 'message':
+                event_type, data = message['data'].decode('utf-8').split(':', 1)
+                yield (event_type, json.loads(data))
 
 
 CLUSTER_ID_INVALID_CHARS = re.compile('[^a-z0-9:-]')
@@ -60,11 +83,14 @@ def get_bool(name: str):
     return os.getenv(name, '').lower() in ('1', 'true')
 
 
+SERVER_PORT = int(os.getenv('SERVER_PORT', 8080))
 DEFAULT_CLUSTERS = 'http://localhost:8001/'
 CREDENTIALS_DIR = os.getenv('CREDENTIALS_DIR', '')
 AUTHORIZE_URL = os.getenv('AUTHORIZE_URL')
 APP_URL = os.getenv('APP_URL')
 MOCK = get_bool('MOCK')
+REDIS_URL = os.getenv('REDIS_URL')
+STORE = RedisStore(REDIS_URL) if REDIS_URL else MemoryStore()
 
 app = Flask(__name__)
 app.debug = get_bool('DEBUG')
@@ -332,25 +358,25 @@ def get_auth_oauth_token():
 
 def update():
     while True:
-        try:
-            STORE.acquire_lock()
-            if MOCK:
-                clusters = get_mock_clusters()
-            else:
-                clusters = get_kubernetes_clusters()
-            for cluster in clusters:
-                STORE.publish('clusterupdate', cluster)
-        except:
-            logging.exception('Failed to update')
-        finally:
-            STORE.release_lock()
+        lock = STORE.acquire_lock()
+        if lock:
+            try:
+                if MOCK:
+                    clusters = get_mock_clusters()
+                else:
+                    clusters = get_kubernetes_clusters()
+                for cluster in clusters:
+                    STORE.publish('clusterupdate', cluster)
+            except:
+                logging.exception('Failed to update')
+            finally:
+                STORE.release_lock(lock)
         gevent.sleep(5)
 
 
 if __name__ == '__main__':
     logging.basicConfig(level=logging.INFO)
-    port = 8080
-    http_server = gevent.wsgi.WSGIServer(('0.0.0.0', port), app)
+    http_server = gevent.wsgi.WSGIServer(('0.0.0.0', SERVER_PORT), app)
     gevent.spawn(update)
-    logging.info('Listening on :{}..'.format(port))
+    logging.info('Listening on :{}..'.format(SERVER_PORT))
     http_server.serve_forever()
diff --git a/requirements.txt b/requirements.txt
index e3ec8fd..502df59 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,3 +3,4 @@ Flask-OAuthlib
 gevent
 requests
 stups-tokens>=1.0.19
+redlock-py