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.

Lambda Custom

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 −

Configure Events

Now, save the event and test it.

Save Event

The corresponding log output is as shown here −

Custom Output

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 −

Custom Command Prompt

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 −

Configure Sample Event

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);};

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

Payload Command
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