Merge pull request #1 from ImmobilienScout24/message_format

Message format

src/main/python/crassus/deployer.py

@@ -1,6 +1,7 @@
-import boto3
-import logging
 import json
+import logging
+
+import boto3
 from botocore.exceptions import ClientError
 
 logger = logging.getLogger('crassus-deployer')
@@ -15,59 +16,42 @@
 
 def deploy_stack(event, context):
     logger.debug('Received event: %s', event)
-    stack_name, notification_arn, update_parameters = parse_event(event)
-    logger.debug('Extracted: %s, %s, %s', stack_name, notification_arn, update_parameters)
-    stack = load_stack(stack_name, notification_arn)
+    stack_update_parameters = parse_event(event)
+    logger.debug('Extracted: %s', stack_update_parameters)
+    stack = load_stack(stack_update_parameters.stack_name)
     logger.debug('Found stack: %s', stack)
 
-    update_stack(stack, update_parameters, notification_arn)
+    update_stack(stack, stack_update_parameters)
 
 
 def parse_event(event):
-    payload = json.loads(event['Records'][0]['Sns']['Message'])
-    payload_parameters = payload['params']
-
-    update_parameters = map(map_cloudformation_parameters, payload_parameters)
-
-    return payload['stackName'], payload['notificationARN'], update_parameters
-
-
-def map_cloudformation_parameters(parameter):
-    cloudformation_parameter = {}
-
-    cloudformation_parameter['ParameterKey'] = parameter["updateParameterKey"]
-    cloudformation_parameter['ParameterValue'] = parameter["updateParameterValue"]
-
-    return cloudformation_parameter
+    message = json.loads(event['Records'][0]['Sns']['Message'])
+    return StackUpdateParameter(message)
 
 
-def load_stack(stack_name, notification_arn):
+def load_stack(stack_name):
     cloudformation = boto3.resource('cloudformation')
     stack = cloudformation.Stack(stack_name)
 
     try:
         stack.load()
     except ClientError as error:
         logger.error(MESSAGE_STACK_NOT_FOUND.format(stack_name, error.message))
-        notify(MESSAGE_STACK_NOT_FOUND.format(stack_name, error.message), notification_arn)
 
     return stack
 
-def update_stack(stack, update_parameters, notification_arn):
-    stack_parameters = stack.parameters
-    merged = merge_stack_parameters(update_parameters, stack_parameters)
+
+def update_stack(stack, stack_update_parameters):
+    merged = stack_update_parameters.merge(stack.parameters)
     try:
         stack.update(UsePreviousTemplate=True,
                      Parameters=merged,
-                     NotificationARNs=[
-                         notification_arn
-                     ],
                      Capabilities=[
                          'CAPABILITY_IAM',
                      ])
     except ClientError as error:
         logger.error(MESSAGE_UPDATE_PROBLEM.format(stack.name, error.message))
-        notify(MESSAGE_UPDATE_PROBLEM.format(stack.name, error.message), notification_arn)
+
 
 def merge_stack_parameters(update_parameters, stack_parameters):
     merged_stack_parameters = []
@@ -84,9 +68,38 @@ def merge_stack_parameters(update_parameters, stack_parameters):
 
     return merged_stack_parameters
 
+
 def notify(message, notification_arn):
     sns = boto3.resource('sns')
     notification_topic = sns.Topic(notification_arn)
     notification_topic.publish(Message=message,
                                Subject=NOTIFICATION_SUBJECT,
                                MessageStructure='string')
+
+
+class StackUpdateParameter(dict):
+
+    def __init__(self, message):
+        self.version = message['version']
+        self.stack_name = message['stackName']
+        self.region = message['region']
+        self.update(message['parameters'])
+
+    def to_aws_format(self):
+        return [{"ParameterKey": k, "ParameterValue": v}
+                for k, v in self.items()]
+
+    def merge(self, stack_parameters):
+        merged_stack_parameters = []
+        update_parameters = self.to_aws_format()
+
+        for stack_parameter in stack_parameters:
+            for update_parameter in update_parameters:
+                if update_parameter['ParameterKey'] in stack_parameter.values():
+                    merged_stack_parameters.append(update_parameter)
+                else:
+                    stack_parameter['UsePreviousValue'] = True
+                    del stack_parameter['ParameterValue']
+                    merged_stack_parameters.append(stack_parameter)
+
+        return merged_stack_parameters