feat(core): validate maximum amount of resources in a stack

packages/@aws-cdk/core/README.md

@@ -843,3 +843,11 @@ IAM operator, we need it in the *key* of a `StringEquals` condition. JSON keys
 *must be* strings, so to circumvent this limitation, we use `CfnJson`
 to "delay" the rendition of this template section to deploy-time. This means
 that the value of `StringEquals` in the template will be `{ "Fn::GetAtt": [ "ConditionJson", "Value" ] }`, and will only "expand" to the operator we synthesized during deployment.
+
+### Stack Resource Limit
+
+When deploying to AWS CloudFormation, it needs to keep in check the amount of resources being added inside a Stack. Currently it's possible to check the limits in the [AWS CloudFormation quotas](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/cloudformation-limits.html) page.
+
+It's possible to synthesize the project with more Resources than the allowed (or even reduce the number of Resources).
+
+Set the context key `@aws-cdk/core:stackResourceLimit` with the proper value, being 0 for disable the limit of resources.

packages/@aws-cdk/core/lib/stack.ts

@@ -27,8 +27,12 @@ import { Construct as CoreConstruct } from './construct-compat';
 const STACK_SYMBOL = Symbol.for('@aws-cdk/core.Stack');
 const MY_STACK_CACHE = Symbol.for('@aws-cdk/core.Stack.myStack');
 
+export const STACK_RESOURCE_LIMIT_CONTEXT = '@aws-cdk/core:stackResourceLimit';
+
 const VALID_STACK_NAME_REGEX = /^[A-Za-z][A-Za-z0-9-]*$/;
 
+const MAX_RESOURCES = 500;
+
 export interface StackProps {
   /**
    * A description of the stack.
@@ -753,6 +757,17 @@ export class Stack extends CoreConstruct implements ITaggable {
 
     // write the CloudFormation template as a JSON file
     const outPath = path.join(builder.outdir, this.templateFile);
+
+    if (this.maxResources > 0) {
+      const resources = template.Resources || {};
+      const numberOfResources = Object.keys(resources).length;
+
+      if (numberOfResources > this.maxResources) {
+        throw new Error(`Number of resources: ${numberOfResources} is greater than allowed maximum of ${this.maxResources}`);
+      } else if (numberOfResources >= (this.maxResources * 0.8)) {
+        Annotations.of(this).addInfo(`Number of resources: ${numberOfResources} is approaching allowed maximum of ${this.maxResources}`);
+      }
+    }
     fs.writeFileSync(outPath, JSON.stringify(template, undefined, 2));
 
     for (const ctx of this._missingContext) {
@@ -907,6 +922,16 @@ export class Stack extends CoreConstruct implements ITaggable {
     };
   }
 
+  /**
+   * Maximum number of resources in the stack
+   *
+   * Set to 0 to mean "unlimited".
+   */
+  private get maxResources(): number {
+    const contextLimit = this.node.tryGetContext(STACK_RESOURCE_LIMIT_CONTEXT);
+    return contextLimit !== undefined ? parseInt(contextLimit, 10) : MAX_RESOURCES;
+  }
+
   /**
    * Check whether this stack has a (transitive) dependency on another stack
    *

packages/@aws-cdk/core/test/stack.test.ts

@@ -45,6 +45,68 @@ nodeunitShim({
     test.done();
   },
 
+  'when stackResourceLimit is default, should give error'(test: Test) {
+    // GIVEN
+    const app = new App({});
+
+    const stack = new Stack(app, 'MyStack');
+
+    // WHEN
+    for (let index = 0; index < 1000; index++) {
+      new CfnResource(stack, `MyResource-${index}`, { type: 'MyResourceType' });
+    }
+
+    test.throws(() => {
+      app.synth();
+    }, 'Number of resources: 1000 is greater than allowed maximum of 500');
+
+    test.done();
+  },
+
+  'when stackResourceLimit is defined, should give the proper error'(test: Test) {
+    // GIVEN
+    const app = new App({
+      context: {
+        '@aws-cdk/core:stackResourceLimit': 100,
+      },
+    });
+
+    const stack = new Stack(app, 'MyStack');
+
+    // WHEN
+    for (let index = 0; index < 200; index++) {
+      new CfnResource(stack, `MyResource-${index}`, { type: 'MyResourceType' });
+    }
+
+    test.throws(() => {
+      app.synth();
+    }, 'Number of resources: 200 is greater than allowed maximum of 100');
+
+    test.done();
+  },
+
+  'when stackResourceLimit is 0, should not give error'(test: Test) {
+    // GIVEN
+    const app = new App({
+      context: {
+        '@aws-cdk/core:stackResourceLimit': 0,
+      },
+    });
+
+    const stack = new Stack(app, 'MyStack');
+
+    // WHEN
+    for (let index = 0; index < 1000; index++) {
+      new CfnResource(stack, `MyResource-${index}`, { type: 'MyResourceType' });
+    }
+
+    test.doesNotThrow(() => {
+      app.synth();
+    });
+
+    test.done();
+  },
+
   'stack.templateOptions can be used to set template-level options'(test: Test) {
     const stack = new Stack();