feat: create Java cfn-response equivalent (#558) (#560)

* Create Java cfn-response equivalent (#558) Introduces Java implementation of cfn-response module based on NodeJS design. Put the sole class in a separate powertools-cloudformation Maven module. 100% code coverage Addresses #558 * Add base RequestHandler class for custom resources Provides abstract methods for generating the Response to be sent, represented as its own type. Use Objects::nonNull instead of custom method. Addresses #558 * Put Response body attributes (status, noEcho, etc) in Response builder itself Instead of method args to various CloudFormationResponse::send methods, reducing the number of polymorphic send methods to two: one with a Response arg and one without. Rename ResponseException to CustomResourceResponseException. AbstractCustomResourceHandlerTest simplifications. * Lock down CloudFormationResponse; default SdkHttpClient - Include powertools-cloudformation in .github config - Address mutatable ObjectMapper spotbugs finding - JavaDoc cleanup * Cloudformation module documentation * CloudFormation documentation tweaks * Include custom resources doc in menu Co-authored-by: Joe Wolf <[email protected]>
aws-powertools · Oct 26, 2021 · 35ad5f6 · 35ad5f6
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diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
@@ -5,6 +5,7 @@ on:
     branches:
       - master
     paths:
+      - 'powertools-cloudformation/**'
       - 'powertools-core/**'
       - 'powertools-logging/**'
       - 'powertools-sqs/**'
@@ -19,6 +20,7 @@ on:
     branches:
       - master
     paths:
+      - 'powertools-cloudformation/**'
       - 'powertools-core/**'
       - 'powertools-logging/**'
       - 'powertools-sqs/**'

diff --git a/.github/workflows/spotbugs.yml b/.github/workflows/spotbugs.yml
@@ -5,6 +5,7 @@ on:
     branches:
       - master
     paths:
+      - 'powertools-cloudformation/**'
       - 'powertools-core/**'
       - 'powertools-logging/**'
       - 'powertools-sqs/**'

diff --git a/docs/utilities/custom_resources.md b/docs/utilities/custom_resources.md
@@ -0,0 +1,178 @@
+---
+title: Custom Resources description: Utility
+---
+
+[Custom resources](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/template-custom-resources.html)
+provide a way for [AWS Lambda functions](
+https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/template-custom-resources-lambda.html) to execute
+provisioning logic whenever CloudFormation stacks are created, updated, or deleted. The CloudFormation utility enables
+developers to write these Lambda functions in Java.
+
+The utility provides a base `AbstractCustomResourceHandler` class which handles [custom resource request events](
+https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/crpg-ref-requests.html), constructs
+[custom resource responses](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/crpg-ref-responses.html), and
+sends them to the custom resources. Subclasses implement the provisioning logic and configure certain properties of
+these response objects.
+
+## Install
+
+To install this utility, add the following dependency to your project.
+
+=== "Maven"
+
+    ```xml
+    <dependency>
+        <groupId>software.amazon.lambda</groupId>
+        <artifactId>powertools-cloudformation</artifactId>
+        <version>1.7.3</version>
+    </dependency>
+    ```
+
+=== "Gradle"
+
+    ```groovy
+     dependencies {
+        ...
+        implementation 'software.amazon.lambda:powertools-cloudformation:1.7.3'
+        aspectpath 'software.amazon.lambda:powertools-cloudformation:1.7.3'
+    }
+    ```
+
+## Usage
+
+Create a new `AbstractCustomResourceHandler` subclass and implement the `create`, `update`, and `delete` methods with
+provisioning logic in the appropriate methods(s).
+
+As an example, if a Lambda function only needs to provision something when a stack is created, put the provisioning
+logic exclusively within the `create` method; the other methods can just return `null`.
+
+```java hl_lines="8 9 10 11"
+import com.amazonaws.services.lambda.runtime.Context;
+import com.amazonaws.services.lambda.runtime.events.CloudFormationCustomResourceEvent;
+import software.amazon.lambda.powertools.cloudformation.AbstractCustomResourceHandler;
+import software.amazon.lambda.powertools.cloudformation.Response;
+
+public class ProvisionOnCreateHandler extends AbstractCustomResourceHandler {
+
+    @Override
+    protected Response create(CloudFormationCustomResourceEvent createEvent, Context context) {
+        doProvisioning();
+        return Response.success();
+    }
+
+    @Override
+    protected Response update(CloudFormationCustomResourceEvent updateEvent, Context context) {
+        return null;
+    }
+
+    @Override
+    protected Response delete(CloudFormationCustomResourceEvent deleteEvent, Context context) {
+        return null;
+    }
+}
+```
+
+### Signaling Provisioning Failures
+
+If provisioning fails, the stack creation/modification/deletion as a whole can be failed by either throwing a
+`RuntimeException` or by explicitly returning a `Response` with a failed status, e.g. `Response.failure()`.
+
+### Configuring Response Objects
+
+When provisioning results in data to be shared with other parts of the stack, include this data within the returned
+`Response` instance.
+
+This Lambda function creates a [Chime AppInstance](https://docs.aws.amazon.com/chime/latest/dg/create-app-instance.html)
+and maps the returned ARN to a "ChimeAppInstanceArn" attribute.
+
+```java hl_lines="11 12 13 14"
+public class ChimeAppInstanceHandler extends AbstractCustomResourceHandler {
+    @Override
+    protected Response create(CloudFormationCustomResourceEvent createEvent, Context context) {
+        CreateAppInstanceRequest chimeRequest = CreateAppInstanceRequest.builder()
+                .name("my-app-name")
+                .build();
+        CreateAppInstanceResponse chimeResponse = ChimeClient.builder()
+                .region("us-east-1")
+                .createAppInstance(chimeRequest);
+
+        Map<String, String> chimeAtts = Map.of("ChimeAppInstanceArn", chimeResponse.appInstanceArn());
+        return Response.builder()
+                .value(chimeAtts)
+                .build();
+    }
+}
+```
+
+For the example above the following response payload will be sent.
+
+```json
+{
+  "Status": "SUCCESS",
+  "PhysicalResourceId": "2021/10/01/e3a37e552eff4718a5675c1e31f0649e",
+  "StackId": "arn:aws:cloudformation:us-east-1:123456789000:stack/Custom-stack/59e4d2d0-2fe2-10ec-b00e-124d7c1c5f15",
+  "RequestId": "7cae0346-0359-4dff-b80a-a82f247467b6",
+  "LogicalResourceId:": "ChimeTriggerResource",
+  "NoEcho": false,
+  "Data": {
+    "ChimeAppInstanceArn": "arn:aws:chime:us-east-1:123456789000:app-instance/150972c2-5490-49a9-8ba7-e7da4257c16a"
+  }
+}
+```
+
+Once the custom resource receives this response, it's "ChimeAppInstanceArn" attribute is set and the
+[Fn::GetAtt function](
+https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-getatt.html) may be used to
+retrieve the attribute value and make it available to other resources in the stack.
+
+#### Sensitive Response Data
+
+If any attributes are sensitive, enable the "noEcho" flag to mask the output of the custom resource when it's retrieved
+with the Fn::GetAtt function.
+
+```java hl_lines="6"
+public class SensitiveDataHandler extends AbstractResourceHandler {
+    @Override
+    protected Response create(CloudFormationCustomResourceEvent createEvent, Context context) {
+        return Response.builder()
+                .value(Map.of("SomeSecret", sensitiveValue))
+                .noEcho(true)
+                .build();
+    }
+}
+```
+
+#### Customizing Serialization
+
+Although using a `Map` as the Response's value is the most straightforward way to provide attribute name/value pairs,
+any arbitrary `java.lang.Object` may be used. By default, these objects are serialized with an internal Jackson
+`ObjectMapper`. If the object requires special serialization logic, a custom `ObjectMapper` can be specified.
+
+```java hl_lines="21 22 23 24"
+public class CustomSerializationHandler extends AbstractResourceHandler {
+    /**
+     * Type representing the custom response Data. 
+     */
+    static class Policy {
+        public ZonedDateTime getExpires() {
+            return ZonedDateTime.now().plusDays(10);
+        }
+    }
+
+    /**
+     * Mapper for serializing Policy instances.
+     */
+    private final ObjectMapper policyMapper = new ObjectMapper()
+            .registerModule(new JavaTimeModule())
+            .disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
+
+    @Override
+    protected Response create(CloudFormationCustomResourceEvent createEvent, Context context) {
+        Policy policy = new Policy();
+        return Response.builder()
+                .value(policy)
+                .objectMapper(policyMapper) // customize serialization
+                .build();
+    }
+}
+```
diff --git a/mkdocs.yml b/mkdocs.yml
@@ -13,6 +13,7 @@ nav:
       - utilities/sqs_large_message_handling.md
       - utilities/batch.md
       - utilities/validation.md
+      - utilities/custom_resources.md
 
 theme:
   name: material

diff --git a/pom.xml b/pom.xml
@@ -35,6 +35,7 @@
         <module>powertools-parameters</module>
         <module>powertools-validation</module>
         <module>powertools-test-suite</module>
+        <module>powertools-cloudformation</module>
     </modules>
 
     <scm>
@@ -121,6 +122,16 @@
                 <type>pom</type>
                 <scope>import</scope>
             </dependency>
+            <dependency>
+                <groupId>software.amazon.awssdk</groupId>
+                <artifactId>http-client-spi</artifactId>
+                <version>${aws.sdk.version}</version>
+            </dependency>
+            <dependency>
+                <groupId>software.amazon.awssdk</groupId>
+                <artifactId>url-connection-client</artifactId>
+                <version>${aws.sdk.version}</version>
+            </dependency>
             <dependency>
                 <groupId>io.burt</groupId>
                 <artifactId>jmespath-jackson</artifactId>

diff --git a/powertools-cloudformation/pom.xml b/powertools-cloudformation/pom.xml
@@ -0,0 +1,98 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>powertools-cloudformation</artifactId>
+    <packaging>jar</packaging>
+
+    <parent>
+        <artifactId>powertools-parent</artifactId>
+        <groupId>software.amazon.lambda</groupId>
+        <version>1.7.3</version>
+    </parent>
+
+    <name>AWS Lambda Powertools Java library Cloudformation</name>
+    <description>
+        A suite of utilities for AWS Lambda Functions that makes tracing with AWS X-Ray, structured logging and creating
+        custom metrics asynchronously easier.
+    </description>
+    <url>https://aws.amazon.com/lambda/</url>
+    <issueManagement>
+        <system>GitHub Issues</system>
+        <url>https://github.com/awslabs/aws-lambda-powertools-java/issues</url>
+    </issueManagement>
+    <scm>
+        <url>https://github.com/awslabs/aws-lambda-powertools-java.git</url>
+    </scm>
+    <developers>
+        <developer>
+            <name>AWS Lambda Powertools team</name>
+            <organization>Amazon Web Services</organization>
+            <organizationUrl>https://aws.amazon.com/</organizationUrl>
+        </developer>
+    </developers>
+
+    <distributionManagement>
+        <snapshotRepository>
+            <id>ossrh</id>
+            <url>https://aws.oss.sonatype.org/content/repositories/snapshots</url>
+        </snapshotRepository>
+    </distributionManagement>
+
+    <dependencies>
+        <dependency>
+            <groupId>software.amazon.awssdk</groupId>
+            <artifactId>http-client-spi</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>software.amazon.awssdk</groupId>
+            <artifactId>url-connection-client</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>com.amazonaws</groupId>
+            <artifactId>aws-lambda-java-core</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>com.amazonaws</groupId>
+            <artifactId>aws-lambda-java-events</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-databind</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.aspectj</groupId>
+            <artifactId>aspectjrt</artifactId>
+        </dependency>
+
+        <!-- Test dependencies -->
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-api</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-engine</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-params</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-core</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+</project>