feat(cli): support for hotswapping Lambda Versions and Aliases (#18145)

This extends the existing hotswapping support for Lambda Functions to also work for Versions and Aliases.

Implementation-wise, this required quite a bit of changes, as Versions are immutable in CloudFormation,
and the only way you can change them is by replacing them;
so, we had to add the notion of replacement changes to our hotswapping logic
(as, up to this point, they were simply a pair of "delete" and "add" changes,
which would result in hotswapping determining it can't proceed,
and falling back to a full CloudFormation deployment).

I also modified the main hotswapping algorithm:
now, a resource change is considered non-hotswappable if all detectors return `REQUIRES_FULL_DEPLOYMENT` for it;
if at least one detector returns `IRRELEVANT`, we ignore this change.
This allows us to get rid of the awkward `EmptyHotswapOperation` that we had to use before in these situations.

I also made a few small tweaks to the printing messages added in #18058:
I no longer prefix them with the name of the service,
as now hotswapping can affect different resource types, and it looked a bit awkward with that prefix present.

Fixes #17043

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/aws-cdk/README.md

@@ -362,7 +362,8 @@ and that you have the necessary IAM permissions to update the resources that are
 Hotswapping is currently supported for the following changes
 (additional changes will be supported in the future):
 
-- Code asset changes of AWS Lambda functions.
+- Code asset and tag changes of AWS Lambda functions.
+- AWS Lambda Versions and Aliases changes.
 - Definition changes of AWS Step Functions State Machines.
 - Container asset changes of AWS ECS Services.
 - Website asset changes of AWS S3 Bucket Deployments.

packages/aws-cdk/lib/api/hotswap-deployments.ts

@@ -61,11 +61,12 @@ export async function tryHotswapDeployment(
 async function findAllHotswappableChanges(
   stackChanges: cfn_diff.TemplateDiff, evaluateCfnTemplate: EvaluateCloudFormationTemplate,
 ): Promise<HotswapOperation[] | undefined> {
+  const resourceDifferences = getStackResourceDifferences(stackChanges);
+
   let foundNonHotswappableChange = false;
   const promises: Array<Array<Promise<ChangeHotswapResult>>> = [];
-
   // gather the results of the detector functions
-  stackChanges.resources.forEachDifference((logicalId: string, change: cfn_diff.ResourceDifference) => {
+  for (const [logicalId, change] of Object.entries(resourceDifferences)) {
     const resourceHotswapEvaluation = isCandidateForHotswapping(change);
 
     if (resourceHotswapEvaluation === ChangeHotswapImpact.REQUIRES_FULL_DEPLOYMENT) {
@@ -81,17 +82,16 @@ async function findAllHotswappableChanges(
         isHotswappableCodeBuildProjectChange(logicalId, resourceHotswapEvaluation, evaluateCfnTemplate),
       ]);
     }
-  });
+  }
 
+  // resolve all detector results
   const changesDetectionResults: Array<Array<ChangeHotswapResult>> = [];
   for (const detectorResultPromises of promises) {
     const hotswapDetectionResults = await Promise.all(detectorResultPromises);
     changesDetectionResults.push(hotswapDetectionResults);
   }
 
   const hotswappableResources = new Array<HotswapOperation>();
-
-  // resolve all detector results
   for (const hotswapDetectionResults of changesDetectionResults) {
     const perChangeHotswappableResources = new Array<HotswapOperation>();
 
@@ -107,23 +107,94 @@ async function findAllHotswappableChanges(
       continue;
     }
 
-    // no hotswappable changes found, so any REQUIRES_FULL_DEPLOYMENTs imply a non-hotswappable change
-    for (const result of hotswapDetectionResults) {
-      if (result === ChangeHotswapImpact.REQUIRES_FULL_DEPLOYMENT) {
-        foundNonHotswappableChange = true;
-      }
+    // no hotswappable changes found, so at least one IRRELEVANT means we can ignore this change;
+    // otherwise, all answers are REQUIRES_FULL_DEPLOYMENT, so this means we can't hotswap this change,
+    // and have to do a full deployment instead
+    if (!hotswapDetectionResults.some(hdr => hdr === ChangeHotswapImpact.IRRELEVANT)) {
+      foundNonHotswappableChange = true;
     }
-    // no REQUIRES_FULL_DEPLOYMENT implies that all results are IRRELEVANT
   }
 
   return foundNonHotswappableChange ? undefined : hotswappableResources;
 }
 
+/**
+ * Returns all changes to resources in the given Stack.
+ *
+ * @param stackChanges the collection of all changes to a given Stack
+ */
+function getStackResourceDifferences(stackChanges: cfn_diff.TemplateDiff): { [logicalId: string]: cfn_diff.ResourceDifference } {
+  // we need to collapse logical ID rename changes into one change,
+  // as they are represented in stackChanges as a pair of two changes: one addition and one removal
+  const allResourceChanges: { [logId: string]: cfn_diff.ResourceDifference } = stackChanges.resources.changes;
+  const allRemovalChanges = filterDict(allResourceChanges, resChange => resChange.isRemoval);
+  const allNonRemovalChanges = filterDict(allResourceChanges, resChange => !resChange.isRemoval);
+  for (const [logId, nonRemovalChange] of Object.entries(allNonRemovalChanges)) {
+    if (nonRemovalChange.isAddition) {
+      const addChange = nonRemovalChange;
+      // search for an identical removal change
+      const identicalRemovalChange = Object.entries(allRemovalChanges).find(([_, remChange]) => {
+        return changesAreForSameResource(remChange, addChange);
+      });
+      // if we found one, then this means this is a rename change
+      if (identicalRemovalChange) {
+        const [removedLogId, removedResourceChange] = identicalRemovalChange;
+        allNonRemovalChanges[logId] = makeRenameDifference(removedResourceChange, addChange);
+        // delete the removal change that forms the rename pair
+        delete allRemovalChanges[removedLogId];
+      }
+    }
+  }
+  // the final result are all of the remaining removal changes,
+  // plus all of the non-removal changes
+  // (we saved the rename changes in that object already)
+  return {
+    ...allRemovalChanges,
+    ...allNonRemovalChanges,
+  };
+}
+
+/** Filters an object with string keys based on whether the callback returns 'true' for the given value in the object. */
+function filterDict<T>(dict: { [key: string]: T }, func: (t: T) => boolean): { [key: string]: T } {
+  return Object.entries(dict).reduce((acc, [key, t]) => {
+    if (func(t)) {
+      acc[key] = t;
+    }
+    return acc;
+  }, {} as { [key: string]: T });
+}
+
+/** Returns 'true' if a pair of changes is for the same resource. */
+function changesAreForSameResource(oldChange: cfn_diff.ResourceDifference, newChange: cfn_diff.ResourceDifference): boolean {
+  return oldChange.oldResourceType === newChange.newResourceType &&
+      // this isn't great, but I don't want to bring in something like underscore just for this comparison
+      JSON.stringify(oldChange.oldProperties) === JSON.stringify(newChange.newProperties);
+}
+
+function makeRenameDifference(
+  remChange: cfn_diff.ResourceDifference,
+  addChange: cfn_diff.ResourceDifference,
+): cfn_diff.ResourceDifference {
+  return new cfn_diff.ResourceDifference(
+    // we have to fill in the old value, because otherwise this will be classified as a non-hotswappable change
+    remChange.oldValue,
+    addChange.newValue,
+    {
+      resourceType: {
+        oldType: remChange.oldResourceType,
+        newType: addChange.newResourceType,
+      },
+      propertyDiffs: (addChange as any).propertyDiffs,
+      otherDiffs: (addChange as any).otherDiffs,
+    },
+  );
+}
+
 /**
  * returns `ChangeHotswapImpact.REQUIRES_FULL_DEPLOYMENT` if a resource was deleted, or a change that we cannot short-circuit occured.
  * Returns `ChangeHotswapImpact.IRRELEVANT` if a change that does not impact shortcircuiting occured, such as a metadata change.
  */
-export function isCandidateForHotswapping(change: cfn_diff.ResourceDifference): HotswappableChangeCandidate | ChangeHotswapImpact {
+function isCandidateForHotswapping(change: cfn_diff.ResourceDifference): HotswappableChangeCandidate | ChangeHotswapImpact {
   // a resource has been removed OR a resource has been added; we can't short-circuit that change
   if (!change.newValue || !change.oldValue) {
     return ChangeHotswapImpact.REQUIRES_FULL_DEPLOYMENT;
@@ -156,12 +227,12 @@ async function applyHotswappableChange(sdk: ISDK, hotswapOperation: HotswapOpera
 
   try {
     for (const name of hotswapOperation.resourceNames) {
-      print(`   ${ICON} hotswapping ${hotswapOperation.service}: %s`, colors.bold(name));
+      print(`   ${ICON} %s`, colors.bold(name));
     }
     return await hotswapOperation.apply(sdk);
   } finally {
     for (const name of hotswapOperation.resourceNames) {
-      print(`${ICON} ${hotswapOperation.service}: %s %s`, colors.bold(name), colors.green('hotswapped!'));
+      print(`${ICON} %s %s`, colors.bold(name), colors.green('hotswapped!'));
     }
     sdk.removeCustomUserAgent(customUserAgent);
   }

packages/aws-cdk/lib/api/hotswap/code-build-projects.ts

@@ -51,7 +51,7 @@ class ProjectHotswapOperation implements HotswapOperation {
   constructor(
     private readonly updateProjectInput: AWS.CodeBuild.UpdateProjectInput,
   ) {
-    this.resourceNames = [updateProjectInput.name];
+    this.resourceNames = [`CodeBuild project '${updateProjectInput.name}'`];
   }
 
   public async apply(sdk: ISDK): Promise<any> {

packages/aws-cdk/lib/api/hotswap/ecs-services.ts

@@ -83,7 +83,8 @@ class EcsServiceHotswapOperation implements HotswapOperation {
     private readonly taskDefinitionResource: any,
     private readonly servicesReferencingTaskDef: EcsService[],
   ) {
-    this.resourceNames = servicesReferencingTaskDef.map(ecsService => ecsService.serviceArn.split('/')[2]);
+    this.resourceNames = servicesReferencingTaskDef.map(ecsService =>
+      `ECS Service '${ecsService.serviceArn.split('/')[2]}'`);
   }
 
   public async apply(sdk: ISDK): Promise<any> {

packages/aws-cdk/lib/api/hotswap/lambda-functions.ts

@@ -1,5 +1,6 @@
+import { flatMap } from '../../util';
 import { ISDK } from '../aws-auth';
-import { ChangeHotswapImpact, ChangeHotswapResult, HotswapOperation, HotswappableChangeCandidate, establishResourcePhysicalName } from './common';
+import { ChangeHotswapImpact, ChangeHotswapResult, establishResourcePhysicalName, HotswapOperation, HotswappableChangeCandidate } from './common';
 import { EvaluateCloudFormationTemplate } from './evaluate-cloudformation-template';
 
 /**
@@ -11,25 +12,62 @@ import { EvaluateCloudFormationTemplate } from './evaluate-cloudformation-templa
 export async function isHotswappableLambdaFunctionChange(
   logicalId: string, change: HotswappableChangeCandidate, evaluateCfnTemplate: EvaluateCloudFormationTemplate,
 ): Promise<ChangeHotswapResult> {
+  // if the change is for a Lambda Version,
+  // ignore it by returning an empty hotswap operation -
+  // we will publish a new version when we get to hotswapping the actual Function this Version points to, below
+  // (Versions can't be changed in CloudFormation anyway, they're immutable)
+  if (change.newValue.Type === 'AWS::Lambda::Version') {
+    return ChangeHotswapImpact.IRRELEVANT;
+  }
+
+  // we handle Aliases specially too
+  if (change.newValue.Type === 'AWS::Lambda::Alias') {
+    return checkAliasHasVersionOnlyChange(change);
+  }
+
   const lambdaCodeChange = await isLambdaFunctionCodeOnlyChange(change, evaluateCfnTemplate);
   if (typeof lambdaCodeChange === 'string') {
     return lambdaCodeChange;
-  } else {
-    const functionName = await establishResourcePhysicalName(logicalId, change.newValue.Properties?.FunctionName, evaluateCfnTemplate);
-    if (!functionName) {
-      return ChangeHotswapImpact.REQUIRES_FULL_DEPLOYMENT;
-    }
+  }
 
-    const functionArn = await evaluateCfnTemplate.evaluateCfnExpression({
-      'Fn::Sub': 'arn:${AWS::Partition}:lambda:${AWS::Region}:${AWS::AccountId}:function:' + functionName,
-    });
+  const functionName = await establishResourcePhysicalName(logicalId, change.newValue.Properties?.FunctionName, evaluateCfnTemplate);
+  if (!functionName) {
+    return ChangeHotswapImpact.REQUIRES_FULL_DEPLOYMENT;
+  }
+
+  const functionArn = await evaluateCfnTemplate.evaluateCfnExpression({
+    'Fn::Sub': 'arn:${AWS::Partition}:lambda:${AWS::Region}:${AWS::AccountId}:function:' + functionName,
+  });
+
+  // find all Lambda Versions that reference this Function
+  const versionsReferencingFunction = evaluateCfnTemplate.findReferencesTo(logicalId)
+    .filter(r => r.Type === 'AWS::Lambda::Version');
+  // find all Lambda Aliases that reference the above Versions
+  const aliasesReferencingVersions = flatMap(versionsReferencingFunction, v =>
+    evaluateCfnTemplate.findReferencesTo(v.LogicalId));
+  const aliasesNames = await Promise.all(aliasesReferencingVersions.map(a =>
+    evaluateCfnTemplate.evaluateCfnExpression(a.Properties?.Name)));
+
+  return new LambdaFunctionHotswapOperation({
+    physicalName: functionName,
+    functionArn: functionArn,
+    resource: lambdaCodeChange,
+    publishVersion: versionsReferencingFunction.length > 0,
+    aliasesNames,
+  });
+}
 
-    return new LambdaFunctionHotswapOperation({
-      physicalName: functionName,
-      functionArn: functionArn,
-      resource: lambdaCodeChange,
-    });
+/**
+ * Returns  is a given Alias change is only in the 'FunctionVersion' property,
+ * and `ChangeHotswapImpact.REQUIRES_FULL_DEPLOYMENT` is the change is for any other property.
+ */
+function checkAliasHasVersionOnlyChange(change: HotswappableChangeCandidate): ChangeHotswapResult {
+  for (const updatedPropName in change.propertyUpdates) {
+    if (updatedPropName !== 'FunctionVersion') {
+      return ChangeHotswapImpact.REQUIRES_FULL_DEPLOYMENT;
+    }
   }
+  return ChangeHotswapImpact.IRRELEVANT;
 }
 
 /**
@@ -50,7 +88,7 @@ async function isLambdaFunctionCodeOnlyChange(
   }
 
   /*
-   * On first glance, we would want to initialize these using the "previous" values (change.oldValue),
+   * At first glance, we would want to initialize these using the "previous" values (change.oldValue),
    * in case only one of them changed, like the key, and the Bucket stayed the same.
    * However, that actually fails for old-style synthesis, which uses CFN Parameters!
    * Because the names of the Parameters depend on the hash of the Asset,
@@ -60,7 +98,6 @@ async function isLambdaFunctionCodeOnlyChange(
    * even if only one of them was actually changed,
    * which means we don't need the "old" values at all, and we can safely initialize these with just `''`.
    */
-  // Make sure only the code in the Lambda function changed
   const propertyUpdates = change.propertyUpdates;
   let code: LambdaFunctionCode | undefined = undefined;
   let tags: LambdaFunctionTags | undefined = undefined;
@@ -149,14 +186,22 @@ interface LambdaFunctionResource {
   readonly physicalName: string;
   readonly functionArn: string;
   readonly resource: LambdaFunctionChange;
+  readonly publishVersion: boolean;
+  readonly aliasesNames: string[];
 }
 
 class LambdaFunctionHotswapOperation implements HotswapOperation {
   public readonly service = 'lambda-function';
   public readonly resourceNames: string[];
 
   constructor(private readonly lambdaFunctionResource: LambdaFunctionResource) {
-    this.resourceNames = [lambdaFunctionResource.physicalName];
+    this.resourceNames = [
+      `Lambda Function '${lambdaFunctionResource.physicalName}'`,
+      // add Version here if we're publishing a new one
+      ...(lambdaFunctionResource.publishVersion ? [`Lambda Version for Function '${lambdaFunctionResource.physicalName}'`] : []),
+      // add any Aliases that we are hotswapping here
+      ...lambdaFunctionResource.aliasesNames.map(alias => `Lambda Alias '${alias}' for Function '${lambdaFunctionResource.physicalName}'`),
+    ];
   }
 
   public async apply(sdk: ISDK): Promise<any> {
@@ -165,11 +210,44 @@ class LambdaFunctionHotswapOperation implements HotswapOperation {
     const operations: Promise<any>[] = [];
 
     if (resource.code !== undefined) {
-      operations.push(lambda.updateFunctionCode({
+      const updateFunctionCodePromise = lambda.updateFunctionCode({
         FunctionName: this.lambdaFunctionResource.physicalName,
         S3Bucket: resource.code.s3Bucket,
         S3Key: resource.code.s3Key,
-      }).promise());
+      }).promise();
+
+      // only if the code changed is there any point in publishing a new Version
+      if (this.lambdaFunctionResource.publishVersion) {
+        // we need to wait for the code update to be done before publishing a new Version
+        await updateFunctionCodePromise;
+        // if we don't wait for the Function to finish updating,
+        // we can get a "The operation cannot be performed at this time. An update is in progress for resource:"
+        // error when publishing a new Version
+        await lambda.waitFor('functionUpdated', {
+          FunctionName: this.lambdaFunctionResource.physicalName,
+        }).promise();
+
+        const publishVersionPromise = lambda.publishVersion({
+          FunctionName: this.lambdaFunctionResource.physicalName,
+        }).promise();
+
+        if (this.lambdaFunctionResource.aliasesNames.length > 0) {
+          // we need to wait for the Version to finish publishing
+          const versionUpdate = await publishVersionPromise;
+
+          for (const alias of this.lambdaFunctionResource.aliasesNames) {
+            operations.push(lambda.updateAlias({
+              FunctionName: this.lambdaFunctionResource.physicalName,
+              Name: alias,
+              FunctionVersion: versionUpdate.Version,
+            }).promise());
+          }
+        } else {
+          operations.push(publishVersionPromise);
+        }
+      } else {
+        operations.push(updateFunctionCodePromise);
+      }
     }
 
     if (resource.tags !== undefined) {
@@ -184,7 +262,6 @@ class LambdaFunctionHotswapOperation implements HotswapOperation {
           tagsToSet[tagName] = tagValue as string;
         });
 
-
       if (tagsToDelete.length > 0) {
         operations.push(lambda.untagResource({
           Resource: this.lambdaFunctionResource.functionArn,

packages/aws-cdk/lib/api/hotswap/s3-bucket-deployments.ts

@@ -1,5 +1,5 @@
 import { ISDK } from '../aws-auth';
-import { ChangeHotswapImpact, ChangeHotswapResult, HotswapOperation, HotswappableChangeCandidate/*, establishResourcePhysicalName*/ } from './common';
+import { ChangeHotswapImpact, ChangeHotswapResult, HotswapOperation, HotswappableChangeCandidate } from './common';
 import { EvaluateCloudFormationTemplate } from './evaluate-cloudformation-template';
 
 /**
@@ -40,7 +40,7 @@ class S3BucketDeploymentHotswapOperation implements HotswapOperation {
   public readonly resourceNames: string[];
 
   constructor(private readonly functionName: string, private readonly customResourceProperties: any) {
-    this.resourceNames = [this.customResourceProperties.DestinationBucketName];
+    this.resourceNames = [`Contents of S3 Bucket '${this.customResourceProperties.DestinationBucketName}'`];
   }
 
   public async apply(sdk: ISDK): Promise<any> {
@@ -95,7 +95,7 @@ async function changeIsForS3DeployCustomResourcePolicy(
     }
   }
 
-  return new EmptyHotswapOperation();
+  return ChangeHotswapImpact.IRRELEVANT;
 }
 
 function stringifyObject(obj: any): any {
@@ -115,11 +115,3 @@ function stringifyObject(obj: any): any {
   }
   return ret;
 }
-
-class EmptyHotswapOperation implements HotswapOperation {
-  readonly service = 'empty';
-  public readonly resourceNames = [];
-  public async apply(sdk: ISDK): Promise<any> {
-    return Promise.resolve(sdk);
-  }
-}