fix(aws-ecs): correctly sets MinimumHealthyPercentage to 0 (#1661)

Zero is a valid value for MinimumHealthyPercentage and therefore should
not be replaced with the default value.

BaseService now explicitly checks if minimumHealthyPercent is null
before setting default value: fixes #1660

packages/@aws-cdk/aws-ecs/lib/base/base-service.ts

@@ -104,7 +104,7 @@ export abstract class BaseService extends cdk.Construct
       loadBalancers: new cdk.Token(() => this.loadBalancers),
       deploymentConfiguration: {
         maximumPercent: props.maximumPercent || 200,
-        minimumHealthyPercent: props.minimumHealthyPercent || 50
+        minimumHealthyPercent: props.minimumHealthyPercent === undefined ? 50 : props.minimumHealthyPercent
       },
       healthCheckGracePeriodSeconds: props.healthCheckGracePeriodSeconds,
       /* role: never specified, supplanted by Service Linked Role */

packages/@aws-cdk/aws-ecs/test/fargate/test.fargate-service.ts

@@ -129,6 +129,33 @@ export = {
 
       test.done();
     },
+
+    "allows specifying 0 for minimumHealthyPercent"(test: Test) {
+      // GIVEN
+      const stack = new cdk.Stack();
+      const vpc = new ec2.VpcNetwork(stack, 'MyVpc', {});
+      const cluster = new ecs.Cluster(stack, 'EcsCluster', { vpc });
+      const taskDefinition = new ecs.FargateTaskDefinition(stack, 'FargateTaskDef');
+
+      taskDefinition.addContainer("web", {
+        image: ecs.ContainerImage.fromDockerHub("amazon/amazon-ecs-sample"),
+      });
+
+      new ecs.FargateService(stack, "FargateService", {
+        cluster,
+        taskDefinition,
+        minimumHealthyPercent: 0,
+      });
+
+      // THEN
+      expect(stack).to(haveResourceLike("AWS::ECS::Service", {
+        DeploymentConfiguration: {
+          MinimumHealthyPercent: 0,
+        }
+      }));
+
+      test.done();
+    },
   },
 
   "When setting up a health check": {