T87 Made script to read input provided by Consul on watch trigger

The script reads all input and the CONSUL_INDEX env var. It uses the latter
to determine which of the values passed by consul was last modified and
actually triggered the watch.

integrations/consul/consul.cfg

@@ -0,0 +1,9 @@
+{
+  "watches": [
+    {
+      "type": "keyprefix",
+      "prefix": "proxysql/",
+      "handler": "/home/ionut/workspace/proxysql/proxysql/integrations/consul/proxysql-consul.py update"
+    }
+  ]
+}

integrations/consul/proxysql-consul.py

@@ -1,6 +1,8 @@
 #!/usr/bin/env python
 
+import base64
 import json
+import os
 import requests
 import sys
 
@@ -15,7 +17,7 @@ CFG_CONSUL_PORT = 'consul_port'
 
 # Proxysql config types to Consul key mapping
 TYPE_TO_KEY = {
-        'mysql_servers': 'proxysql/mysql_servers'
+        'mysql_servers': 'proxysql/mysql_serverss'
         }
 
 config = {}
@@ -43,6 +45,39 @@ def write_data(proxysql_cfg, proxysql_cfg_type):
     r = requests.put(url, data=proxysql_cfg)
     print r.status_code
 
+
+def update_config():
+    """
+    Reads all input from stdin that is passed by Consul and extracts the config
+    that was modified.
+
+    Consul is configured to watch all proxysql keys and returns all their values
+    when one key is modified. To determine the value that was actually modified
+    we use the CONSUL_INDEX env var written by Consul. This should match the
+    'ModifyIndex' field of the value that triggered the watch.
+
+    Values are returned as a JSON array. The actual value content is stored in
+    the 'Value' field, base64 encoded.
+    """
+    if 'CONSUL_INDEX' not in os.environ:
+        print 'Missing consul index on update request'
+        exit(1)
+    consul_index = int(os.environ['CONSUL_INDEX'])
+    consul_data = sys.stdin.read()
+
+    updated_value = None
+    values = json.loads(consul_data)
+    for value in values:
+        if 'ModifyIndex' in value and value['ModifyIndex'] == consul_index:
+           updated_value = value
+           break
+    if not updated_value:
+        print 'Failed to determine updated config from Consul data'
+        exit(1)
+
+    proxysql_config = base64.b64decode(updated_value['Value'])
+    print proxysql_config
+
 if __name__ == '__main__':
     read_config()
 
@@ -53,5 +88,9 @@ if __name__ == '__main__':
             value = sys.argv[3]
             write_data(key, value)
             exit(0)
+        elif mode == 'update':
+            update_config()
+            exit(0)
+
     print USAGE
     exit(1)