Using Lambda Function with Custom User Applications

We can use AWS lambda function to process using generated events by user application in the following two ways −

• Using AWS Console
• Using AWS CLI

Using AWS Console

From AWS console, we will work with events and AWS Lambda. For this purpose, go to AWS console and create a lambda function.

Next, let us add the code for AWS Lambda −

exports.handler = (event, context, callback) => {
   // TODO implement
   console.log("Hello => "+ event.name);
   console.log("Address =>"+ event.addr);
   callback(null, 'Hello '+event.name +" and address is "+ event.addr);
};

Note that in the above code, we are printing name and address using event.

The details to the event will be given using the test event created as follows −

Now, save the event and test it.

The corresponding log output is as shown here −

Using AWS CLI

We can invoke the above function using AWS CLI as follows −

aws lambda invoke --function-name "lambdauserevent" --log-type Tail --
payload file://C:\clioutput\input.txt C:\clioutput\outputfile.txt

The event details are given to payload and the output is stored at C:\clioutput\outputfile.txt. as follows −

input.txt

{"name":"Roy Singh", "addr":"Mumbai"}

On invoking the Lambda using AWS CLI, you can see the output is as follows −

Similarly, in case you want to test AWS Lambda for any other AWS service, you can do so using the test event in AWS console and AWS CLI. A sample event for SNS service is shown below −

{
   "Records": [{
      "EventVersion": "1.0",
      "EventSubscriptionArn": "arnid",
      "EventSource": "aws:sns",
      "Sns": {
         "SignatureVersion": "1",
         "Timestamp": "1970-01-01T00:00:00.000Z",
         "Signature": "EXAMPLE",
         "SigningCertUrl": "EXAMPLE",
         "MessageId": "95df01b4-ee98-5cb9-9903-4c221d41eb5e",
         "Message": "Hello from SNS!",
         "MessageAttributes": {
            "Test": {
               "Type": "String",
               "Value": "TestString"
            },
            "TestBinary": {
               "Type": "Binary",
               "Value": "TestBinary"
            }
         },
         "Type": "Notification",
         "UnsubscribeUrl": "EXAMPLE",
         "TopicArn": "topicarn",
         "Subject": "TestInvoke"
      }
   }]
}

Let us add the sample event shown above and test it as shown −

In AWS Lambda, code will print the SNS message as shown in the example given below −

exports.handler = (event, context, callback) => {
   // TODO implement
   console.log(event.Records[0].Sns.Message);
   callback(null, event.Records[0].Sns.Message);};

Let us invoke the same using AWS CLI. Let us save the event in a file and use that for payload using the command shown −

aws lambda invoke --function-name "lambdauserevent" --log-type Tail --
payload file://C:\clioutput\sns.txt C:\clioutput\snsoutput.txt