chore(lambda): validate logLevel with logFormat for advanced logging (#…

…28045)

This PR adds to validate whether `applicationLogLevel` and
`systemLogLevel` have a JSON `logFormat` for advanced logging.

The doc states the following:

> To use log-level filtering, your function must be configured to use
the JSON log format. The default log format for all Lambda managed
runtimes is currently plain text. To learn how to configure your
function's log format to JSON, see [Setting your function's log
format](https://docs.aws.amazon.com/lambda/latest/dg/monitoring-cloudwatchlogs.html#monitoring-cloudwatchlogs-set-format).


https://docs.aws.amazon.com/lambda/latest/dg/monitoring-cloudwatchlogs.html#monitoring-cloudwatchlogs-advanced

If you specify `systemLogLevel` or `applicationLogLevel` without
`LogFormat.JSON` like the following code, an error occurred in a CFn
event:
```
Resource handler returned message: "LogLevel is not supported when LogFormat is set to "Text". Remove LogLevel from your request or change the LogFormat to "Json" and try again.
```

```ts
new Function(stack, 'LambdaWithLogLevel', {
  code: new InlineCode('foo'),
  handler: 'index.handler',
  runtime: Runtime.NODEJS_18_X,
  logFormat: LogFormat.TEXT,
  systemLogLevel: SystemLogLevel.INFO,
  applicationLogLevel: ApplicationLogLevel.INFO,
});
```

This validation allows the error to be caught at the synth phase.

----

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

packages/aws-cdk-lib/aws-lambda/README.md

@@ -173,6 +173,8 @@ new lambda.Function(this, 'Lambda', {
 });
 ```
 
+To use `applicationLogLevel` and/or `systemLogLevel` you must set `logFormat` to `LogFormat.JSON`.
+
 ## Resource-based Policies
 
 AWS Lambda supports resource-based policies for controlling access to Lambda

packages/aws-cdk-lib/aws-lambda/lib/function.ts

@@ -1085,6 +1085,10 @@ export class Function extends FunctionBase {
    * function and undefined if not.
    */
   private getLoggingConfig(props: FunctionProps): CfnFunction.LoggingConfigProperty | undefined {
+    if ((props.applicationLogLevel || props.systemLogLevel) && props.logFormat !== LogFormat.JSON) {
+      throw new Error(`To use ApplicationLogLevel and/or SystemLogLevel you must set LogFormat to '${LogFormat.JSON}', got '${props.logFormat}'.`);
+    }
+
     let loggingConfig: CfnFunction.LoggingConfigProperty;
     if (props.logFormat || props.logGroup) {
       loggingConfig = {

packages/aws-cdk-lib/aws-lambda/test/logging-config.test.ts

@@ -133,6 +133,60 @@ describe('logging Config', () => {
           logGroupName: 'customLogGroup',
         }),
       });
-    }).toThrowError('CDK does not support setting logRetention and logGroup');
+    }).toThrow(/CDK does not support setting logRetention and logGroup/);
+  });
+
+  test('Throws when applicationLogLevel is specified with TEXT logFormat', () => {
+    const app = new cdk.App();
+    const stack = new cdk.Stack(app, 'stack');
+    expect(() => {
+      new lambda.Function(stack, 'Lambda', {
+        code: new lambda.InlineCode('foo'),
+        handler: 'index.handler',
+        runtime: lambda.Runtime.NODEJS_18_X,
+        logFormat: lambda.LogFormat.TEXT,
+        applicationLogLevel: lambda.ApplicationLogLevel.INFO,
+      });
+    }).toThrow(/To use ApplicationLogLevel and\/or SystemLogLevel you must set LogFormat to 'JSON', got 'Text'./);
+  });
+
+  test('Throws when systemLogLevel is specified with TEXT logFormat', () => {
+    const app = new cdk.App();
+    const stack = new cdk.Stack(app, 'stack');
+    expect(() => {
+      new lambda.Function(stack, 'Lambda', {
+        code: new lambda.InlineCode('foo'),
+        handler: 'index.handler',
+        runtime: lambda.Runtime.NODEJS_18_X,
+        logFormat: lambda.LogFormat.TEXT,
+        systemLogLevel: lambda.SystemLogLevel.INFO,
+      });
+    }).toThrow(/To use ApplicationLogLevel and\/or SystemLogLevel you must set LogFormat to 'JSON', got 'Text'./);
+  });
+
+  test('Throws when applicationLogLevel is specified if logFormat is undefined', () => {
+    const app = new cdk.App();
+    const stack = new cdk.Stack(app, 'stack');
+    expect(() => {
+      new lambda.Function(stack, 'Lambda', {
+        code: new lambda.InlineCode('foo'),
+        handler: 'index.handler',
+        runtime: lambda.Runtime.NODEJS_18_X,
+        applicationLogLevel: lambda.ApplicationLogLevel.INFO,
+      });
+    }).toThrow(/To use ApplicationLogLevel and\/or SystemLogLevel you must set LogFormat to 'JSON', got 'undefined'./);
+  });
+
+  test('Throws when systemLogLevel is specified if logFormat is undefined', () => {
+    const app = new cdk.App();
+    const stack = new cdk.Stack(app, 'stack');
+    expect(() => {
+      new lambda.Function(stack, 'Lambda', {
+        code: new lambda.InlineCode('foo'),
+        handler: 'index.handler',
+        runtime: lambda.Runtime.NODEJS_18_X,
+        systemLogLevel: lambda.SystemLogLevel.INFO,
+      });
+    }).toThrow(/To use ApplicationLogLevel and\/or SystemLogLevel you must set LogFormat to 'JSON', got 'undefined'./);
   });
 });