add possibility to cache specific ami version (#389)

lib/aurora-serverless.ts

@@ -54,6 +54,7 @@ export class BastionHostAuroraServerlessForward extends BastionHostForward {
       clientTimeout: props.clientTimeout,
       serverTimeout: props.serverTimeout,
       shouldPatch: props.shouldPatch,
+      cachedInContext: props.cachedInContext,
     });
 
     if (props.iamUser !== undefined && props.resourceIdentifier !== undefined) {

lib/bastion-host-forward-base-props.ts

@@ -54,4 +54,25 @@ export interface BastionHostForwardBaseProps {
    * @default true
    */
   readonly shouldPatch?: boolean;
+
+  /**
+   * Whether the AMI ID is cached to be stable between deployments
+   *
+   * By default, the newest image is used on each deployment. This will cause
+   * instances to be replaced whenever a new version is released, and may cause
+   * downtime if there aren't enough running instances in the AutoScalingGroup
+   * to reschedule the tasks on.
+   *
+   * If set to true, the AMI ID will be cached in `cdk.context.json` and the
+   * same value will be used on future runs. Your instances will not be replaced
+   * but your AMI version will grow old over time. To refresh the AMI lookup,
+   * you will have to evict the value from the cache using the `cdk context`
+   * command. See https://docs.aws.amazon.com/cdk/latest/guide/context.html for
+   * more information.
+   *
+   * Can not be set to `true` in environment-agnostic stacks.
+   *
+   * @default false
+   */
+  readonly cachedInContext?: boolean;
 }

lib/bastion-host-forward.ts

@@ -120,6 +120,7 @@ export class BastionHostForward extends Construct {
       machineImage: new AmazonLinuxImage({
         cpuType: AmazonLinuxCpuType.ARM_64,
         generation: AmazonLinuxGeneration.AMAZON_LINUX_2023,
+        cachedInContext: props.cachedInContext,
       }),
       instanceType: InstanceType.of(InstanceClass.T4G, InstanceSize.NANO),
       blockDevices: [

lib/generic-bastion-host-forward.ts

@@ -33,6 +33,7 @@ export class GenericBastionHostForward extends BastionHostForward {
       clientTimeout: props.clientTimeout,
       serverTimeout: props.serverTimeout,
       shouldPatch: props.shouldPatch,
+      cachedInContext: props.cachedInContext,
     });
   }
 }

lib/rds.ts

@@ -55,6 +55,7 @@ export class BastionHostRDSForward extends BastionHostForward {
       clientTimeout: props.clientTimeout,
       serverTimeout: props.serverTimeout,
       shouldPatch: props.shouldPatch,
+      cachedInContext: props.cachedInContext,
     });
 
     if (props.iamUser !== undefined && props.rdsResourceIdentifier !== undefined) {