Validate scheduling strategy for Fargate services (#2559)

* Validate scheduling strategy for Fargate services

* Update test/fixtures/templates/good/resources/ecs/test_fargate_scheduling_strategy.yaml

Co-authored-by: Pat Myron <[email protected]>

* Fix Fargate strategy rule to handle non string properties

Change:

Intrinsic functions can be used for resource properties and previously
this rule checker doesn't handle such scenario.

---------

Co-authored-by: Pat Myron <[email protected]>

docs/rules.md

@@ -132,6 +132,7 @@ The following **151** rules are applied by this linter:
 | [E3041<a name="E3041"></a>](../src/cfnlint/rules/resources/route53/RecordSetName.py) | RecordSet HostedZoneName is a superdomain of Name | In a RecordSet, the HostedZoneName must be a superdomain of the Name being validated |  | [Source](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-route53-recordset.html#cfn-route53-recordset-name) | `resource`,`properties`,`route53` |
 | [E3042<a name="E3042"></a>](../src/cfnlint/rules/resources/ecs/TaskDefinitionEssentialContainer.py) | Check at least one essential container is specified | Check that every TaskDefinition specifies at least one essential container |  | [Source](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-ecs-taskdefinition-containerdefinitions.html#cfn-ecs-taskdefinition-containerdefinition-essential) | `properties`,`ecs`,`task`,`container`,`fargate` |
 | [E3043<a name="E3043"></a>](../src/cfnlint/rules/resources/cloudformation/NestedStackParameters.py) | Validate parameters for in a nested stack | Evalute if parameters for a nested stack are specified and if parameters are specified for a nested stack that aren't required. |  | [Source](https://github.com/awslabs/cfn-python-lint) | `resources`,`cloudformation` |
+| [E3044<a name="E3044"></a>](../src/cfnlint/rules/resources/ecs/FargateDeploymentSchedulingStrategy.py) | Validate scheduling strategy for Fargate services | Fargate services currently only support REPLICA scheduling strategy |  | [Source](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-ecs-service.html#cfn-ecs-service-schedulingstrategy) | `resources`,`container`, `fargate`, `service` |
 | [E3050<a name="E3050"></a>](../src/cfnlint/rules/resources/iam/RefWithPath.py) | Check if REFing to a IAM resource with path set | Some resources don't support looking up the IAM resource by name. This check validates when a REF is being used and the Path is not '/' |  | [Source](https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_elements.html) | `properties`,`iam` |
 | [E3502<a name="E3502"></a>](../src/cfnlint/rules/resources/properties/JsonSize.py) | Check if a JSON Object is within size limits | Validate properties that are JSON values so that their length is within the limits |  | [Source](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/cloudformation-limits.html) | `resources`,`limits`,`json` |
 | [E3503<a name="E3503"></a>](../src/cfnlint/rules/resources/certificatemanager/DomainValidationOptions.py) | ValidationDomain is superdomain of DomainName | In ValidationDomainOptions, the ValidationDomain must be a superdomain of the DomainName being validated |  | [Source](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-certificatemanager-certificate-domainvalidationoption.html#cfn-certificatemanager-certificate-domainvalidationoption-validationdomain) | `certificate`,`certificatemanager`,`domainvalidationoptions`,`validationdomain` |

src/cfnlint/rules/resources/ecs/FargateDeploymentSchedulingStrategy.py

@@ -0,0 +1,32 @@
+"""
+Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+SPDX-License-Identifier: MIT-0
+"""
+from cfnlint.rules import CloudFormationLintRule, RuleMatch
+
+
+class FargateDeploymentSchedulingStrategy(CloudFormationLintRule):
+    id = "E3044"
+    shortdesc = "Check Fargate service scheduling strategy"
+    description = "Check that Fargate service scheduling strategy is REPLICA"
+    source_url = "https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-ecs-service.html#cfn-ecs-service-schedulingstrategy"
+    tags = ["properties", "ecs", "service", "container", "fargate"]
+
+    def match(self, cfn):
+        matches = []
+        ecs_services = cfn.get_resource_properties(["AWS::ECS::Service"])
+
+        for ecs_service in ecs_services:
+            path = ecs_service["Path"]
+            properties = ecs_service["Value"]
+            if isinstance(properties, dict):
+                launch_type = properties.get("LaunchType", None)
+                if isinstance(launch_type, str) and launch_type == "Fargate":
+                    scheduling_strategy = properties.get("SchedulingStrategy", None)
+                    if (
+                        isinstance(scheduling_strategy, str)
+                        and scheduling_strategy != "REPLICA"
+                    ):
+                        error_message = f"Fargate service only support REPLICA as scheduling strategy at {'/'.join(map(str, path))}"
+                        matches.append(RuleMatch(path, error_message))
+        return matches

src/cfnlint/rules/resources/ecs/TaskDefinitionEssentialContainer.py

@@ -41,8 +41,10 @@ def match(self, cfn):
                     has_essential_container = True
 
             if not has_essential_container:
-                message = "No essential containers defined for {0}"
-                rule_match = RuleMatch(path, message.format("/".join(map(str, path))))
+                error_message = (
+                    f"No essential containers defined for {'/'.join(map(str, path))}"
+                )
+                rule_match = RuleMatch(path, error_message)
                 matches.append(rule_match)
 
         return matches

test/fixtures/templates/bad/resources/ecs/test_fargate_scheduling_strategy.yaml

@@ -0,0 +1,6 @@
+Resources:
+  Service1:
+    Type: AWS::ECS::Service
+    Properties:
+      LaunchType: Fargate
+      SchedulingStrategy: DAEMON

test/fixtures/templates/good/resources/ecs/test_fargate_scheduling_strategy.yaml

@@ -0,0 +1,21 @@
+Resources:
+  Service1:
+    Type: AWS::ECS::Service
+    Properties:
+      LaunchType: Fargate
+      SchedulingStrategy: REPLICA
+  Service2:
+    Type: AWS::ECS::Service
+    Properties:
+      LaunchType: EC2
+      SchedulingStrategy: DAEMON
+  Service3:
+    Type: AWS::ECS::Service
+    Properties:
+      LaunchType: EXTERNAL
+      SchedulingStrategy: DAEMON
+  Service4:
+    Type: AWS::ECS::Service
+    Properties:
+      LaunchType: !Join ["", ["FAR", "GATE"]]
+      SchedulingStrategy: DAEMON

test/unit/rules/resources/ecs/test_fargate_service_scheduling_strategy.py

@@ -0,0 +1,31 @@
+"""
+Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+SPDX-License-Identifier: MIT-0
+"""
+from test.unit.rules import BaseRuleTestCase
+
+from cfnlint.rules.resources.ecs.FargateDeploymentSchedulingStrategy import (
+    FargateDeploymentSchedulingStrategy,
+)
+
+
+class TestFargateServiceSchedulingStrategy(BaseRuleTestCase):
+    """
+    Test that Fargate service has correct scheduling strategy (REPLICA)
+    """
+
+    def setUp(self):
+        super(TestFargateServiceSchedulingStrategy, self).setUp()
+        self.collection.register(FargateDeploymentSchedulingStrategy())
+        self.success_templates = [
+            "test/fixtures/templates/good/resources/ecs/test_fargate_scheduling_strategy.yaml"
+        ]
+
+    def test_file_positive(self):
+        self.helper_file_positive()
+
+    def test_file_negative(self):
+        self.helper_file_negative(
+            "test/fixtures/templates/bad/resources/ecs/test_fargate_scheduling_strategy.yaml",
+            1,
+        )