getting-started-create-function.md

Create a Lambda function with the console

In this Getting Started exercise you create a Lambda function using the AWS Lambda console. Next, you manually invoke the Lambda function using sample event data. AWS Lambda executes the Lambda function and returns results. You then verify execution results, including the logs that your Lambda function created and various CloudWatch metrics.

To create a Lambda function

1. Open the AWS Lambda console.

2. Choose Create a function.

3. For Function name, enter my-function.

4. Choose Create function.

Lambda creates a Node.js function and an execution role that grants the function permission to upload logs. Lambda assumes the execution role when you invoke your function, and uses it to create credentials for the AWS SDK and to read data from event sources.

Use the designer

The Designer shows an overview of your function and its upstream and downstream resources. You can use it to configure triggers, layers, and destinations.

Choose my-function in the designer to return to the function's code and configuration. For scripting languages, Lambda includes sample code that returns a success response. You can edit your function code with the embedded AWS Cloud9 editor as long as your source code doesn't exceed the 3 MB limit.

Invoke the Lambda function

Invoke your Lambda function using the sample event data provided in the console.

To invoke a function

1. In the upper right corner, choose Test.

2. In the Configure test event page, choose Create new test event and in Event template, leave the default Hello World option. Enter an Event name and note the following sample event template:

   {
     "key3": "value3",
     "key2": "value2",
     "key1": "value1"
   }
   

   You can change key and values in the sample JSON, but don't change the event structure. If you do change any keys and values, you must update the sample code accordingly.

3. Choose Create and then choose Test. Each user can create up to 10 test events per function. Those test events are not available to other users.

4. AWS Lambda executes your function on your behalf. The handler in your Lambda function receives and then processes the sample event.

5. Upon successful execution, view results in the console.

   • The Execution result section shows the execution status as succeeded and also shows the function execution results, returned by the return statement.
   • The Summary section shows the key information reported in the Log output section (the REPORT line in the execution log).
   • The Log output section shows the log AWS Lambda generates for each execution. These are the logs written to CloudWatch by the Lambda function. The AWS Lambda console shows these logs for your convenience.

   Note that the Click here link shows logs in the CloudWatch console. The function then adds logs to Amazon CloudWatch in the log group that corresponds to the Lambda function.

6. Run the Lambda function a few times to gather some metrics that you can view in the next step.

7. Choose Monitoring. This page shows graphs for the metrics that Lambda sends to CloudWatch.
   

   For more information on these graphs, see Monitoring functions in the AWS Lambda console.

Clean up

If you are done working with the example function, delete it. You can also delete the execution role that the console created, and the log group that stores the function's logs.

To delete a Lambda function

1. Open the Lambda console Functions page.

2. Choose a function.

3. Choose Actions, and then choose Delete function.

4. Choose Delete.

To delete the log group

1. Open the Log groups page of the Amazon CloudWatch console.

2. Choose the function's log group (/aws/lambda/my-function).

3. Choose Actions, and then choose Delete log group.

4. Choose Yes, Delete.

To delete the execution role

1. Open the Roles page of the AWS Identity and Access Management console.

2. Choose the function's role (my-function-role-31exxmpl)

3. Choose Delete role.

4. Choose Yes, delete.

You can automate the creation and cleanup of functions, roles, and log groups with AWS CloudFormation and the AWS CLI. For fully functional sample applications, see Lambda sample applications.