ECS ServicesStable Waiter fails if DescribeServices response does not include deployments

[TimMullender]

Describe the bug

waiter = ecs_client.get_waiter("services_stable")
waiter.wait(cluster=cluster, services=[service])

The ServicesStable waiter in Boto3 fails for some services with the following error message

"In function length(), invalid type for value: None, expected one of: ['string', 'array', 'object'], received: \"null\""

This appears to happen when the services[*].deployments element is absent from the DescribeServices response

Regression Issue

• Select this option if this issue appears to be a regression.

Expected Behavior

The waiter should wait until the services are stable, and not throw an error

Current Behavior

"errorMessage": "In function length(), invalid type for value: None, expected one of: ['string', 'array', 'object'], received: \"null\"",
    "errorType": "JMESPathTypeError",
    "requestId": "94d7b720-8490-4577-9ce7-93b19726c814",
    "stackTrace": [
       REDACTED
        "  File \"/var/lang/lib/python3.11/site-packages/botocore/waiter.py\", line 55, in wait\n    Waiter.wait(self, **kwargs)\n",
        "  File \"/var/lang/lib/python3.11/site-packages/botocore/waiter.py\", line 348, in wait\n    if acceptor.matcher_func(response):\n",
        "  File \"/var/lang/lib/python3.11/site-packages/botocore/waiter.py\", line 229, in acceptor_matches\n    return expression.search(response) == expected\n",
        "  File \"/var/lang/lib/python3.11/site-packages/jmespath/parser.py\", line 509, in search\n    result = interpreter.visit(self.parsed, value)\n",
        "  File \"/var/lang/lib/python3.11/site-packages/jmespath/visitor.py\", line 94, in visit\n    return method(node, *args, **kwargs)\n",
        "  File \"/var/lang/lib/python3.11/site-packages/jmespath/visitor.py\", line 145, in visit_comparator\n    self.visit(node['children'][0], value),\n",
        "  File \"/var/lang/lib/python3.11/site-packages/jmespath/visitor.py\", line 94, in visit\n    return method(node, *args, **kwargs)\n",
        "  File \"/var/lang/lib/python3.11/site-packages/jmespath/visitor.py\", line 169, in visit_function_expression\n    current = self.visit(child, value)\n",
        "  File \"/var/lang/lib/python3.11/site-packages/jmespath/visitor.py\", line 94, in visit\n    return method(node, *args, **kwargs)\n",
        "  File \"/var/lang/lib/python3.11/site-packages/jmespath/visitor.py\", line 180, in visit_filter_projection\n    if self._is_true(self.visit(comparator_node, element)):\n",
        "  File \"/var/lang/lib/python3.11/site-packages/jmespath/visitor.py\", line 94, in visit\n    return method(node, *args, **kwargs)\n",
        "  File \"/var/lang/lib/python3.11/site-packages/jmespath/visitor.py\", line 259, in visit_not_expression\n    original_result = self.visit(node['children'][0], value)\n",
        "  File \"/var/lang/lib/python3.11/site-packages/jmespath/visitor.py\", line 94, in visit\n    return method(node, *args, **kwargs)\n",
        "  File \"/var/lang/lib/python3.11/site-packages/jmespath/visitor.py\", line 253, in visit_and_expression\n    matched = self.visit(node['children'][0], value)\n",
        "  File \"/var/lang/lib/python3.11/site-packages/jmespath/visitor.py\", line 94, in visit\n    return method(node, *args, **kwargs)\n",
        "  File \"/var/lang/lib/python3.11/site-packages/jmespath/visitor.py\", line 145, in visit_comparator\n    self.visit(node['children'][0], value),\n",
        "  File \"/var/lang/lib/python3.11/site-packages/jmespath/visitor.py\", line 94, in visit\n    return method(node, *args, **kwargs)\n",
        "  File \"/var/lang/lib/python3.11/site-packages/jmespath/visitor.py\", line 171, in visit_function_expression\n    return self._functions.call_function(node['value'], resolved_args)\n",
        "  File \"/var/lang/lib/python3.11/site-packages/jmespath/functions.py\", line 80, in call_function\n    self._validate_arguments(resolved_args, signature, function_name)\n",
        "  File \"/var/lang/lib/python3.11/site-packages/jmespath/functions.py\", line 91, in _validate_arguments\n    return self._type_check(args, signature, function_name)\n",
        "  File \"/var/lang/lib/python3.11/site-packages/jmespath/functions.py\", line 97, in _type_check\n    self._type_check_single(actual[i], allowed_types,\n",
        "  File \"/var/lang/lib/python3.11/site-packages/jmespath/functions.py\", line 111, in _type_check_single\n    raise exceptions.JMESPathTypeError(\n"
    ]

Reproduction Steps

I'm unsure what causes a service to not have the deployments element, the service is deployed using CodeDeploy's Blue/Green deployment

Possible Solution

No response

Additional Information/Context

I believe the line causing the issue is here but I'm unsure what it's trying to achieve by checking deployments

SDK version used

1.35.45

Environment details (OS name and version, etc.)

AWS Lambda, Python 3.11 Runtime

[TimMullender]

Also reproduced with the AWS CLI

aws ecs wait services-stable --cluster ClusterName --services ServiceName

In function length(), invalid type for value: None, expected one of: ['string', 'array', 'object'], received: "null"

[tim-finnigan]

Thanks for reaching out. The line you linked in the waiter model hasn't changed for ~6 years, so I'm not sure if something changed on the with the DescribeServices API that would cause this to no longer work. But per the API documentation it looks like there's no guarantee that deployments would be in the response.

Generally service teams own and maintain waiter models like this, but if there is an issue with the original implementation then this may be a bug to address here — and should also maybe be reviewed at a cross-SDK level. I'll mark this issue for further review.