fixup! Fix: 502 response caused by Function not found during alias updates (#7883)

Author: dsotirho-ucsc

scripts/delete_older_function_versions.py

@@ -36,22 +36,12 @@ def main(argv: list[str]):
     parser.add_argument('--function-version', '-v',
                         type=int,
                         required=True,
-                        help='The version of the function to retain. Versions '
-                             'older than this (minus any buffer) will be '
-                             'deleted.')
-    parser.add_argument('--buffer', '-b',
-                        type=int,
-                        default=0,
-                        help='Number of older versions to retain in addition '
-                             'to the specified version.')
+                        help='The version of the function to retain, along '
+                             'with the preceding one. All older versions will '
+                             'be deleted.')
     args = parser.parse_args(argv)
-    assert args.buffer >= 0, R(
-        'The buffer size cannot be less than zero.', args.buffer)
-    retain_version = args.function_version - args.buffer
-    log.info('Deleting function %r versions older than %r',
-             args.function_name, retain_version)
     functions = LambdaFunctions()
-    functions.delete_older_versions(args.function_name, retain_version)
+    functions.delete_older_versions(args.function_name, args.function_version)
 
 
 if __name__ == '__main__':

src/azul/lambdas.py

@@ -126,17 +126,22 @@ def delete_older_versions(self,
         :param function_name: The fully qualified name of the function
                               e.g. 'azul-service-dev'
 
-        :param function_version: The version of the function to retain. Versions
-                                 older than this will be deleted.
+        :param function_version: The version of the function to retain, along
+                                 with the preceding one.
         """
+        # We retain one previous version to guard against a race condition
+        # caused by the eventual consistency of Lambda alias updates.
+        retain_version = function_version - 1
+        log.info('Deleting function %r versions older than %r',
+                 function_name, retain_version)
         paginator = self._lambda.get_paginator('list_versions_by_function')
         versions = [
             function['Version']
             for page in paginator.paginate(FunctionName=function_name)
             for function in page['Versions']
             if (
                 function['Version'] != '$LATEST'  # The so-called "unpublished" version
-                and int(function['Version']) < function_version
+                and int(function['Version']) < retain_version
             )
         ]
         for version in versions:

terraform/api_gateway.tf.json.template.py

@@ -799,11 +799,7 @@ def add_waf_blocked_alarm(resources: JSON) -> JSON:
                                 'python',
                                 f'{config.project_root}/scripts/delete_older_function_versions.py',
                                 '--function-name ${aws_lambda_alias.%s.function_name}' % resource_name,
-                                '--function-version ${aws_lambda_alias.%s.function_version}' % resource_name,
-                                # Retain a previous version to guard against the
-                                # race condition caused by eventual consistency
-                                # of Lambda alias updates.
-                                '--buffer 1'
+                                '--function-version ${aws_lambda_alias.%s.function_version}' % resource_name
                             ])
                         }
                     }