[975] Creating a POSTMAN Api | AWS API Gateway Passing Data to AWS Lambda

ref: AWS Lambda Function URLs

ref: Guide to AWS Lambda Function URLs

ref: Test your Lambda function with Postman

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1. Create a Lambda Function

aws -> Services -> Lambda

2. Edit basic settings

The internal error in Postman test, sometimes it's because the function's running time is too long. Change the timeout time can fix this error as follows.

Changing the timeout value is very important, otherwise the function often raise the issue of "internal sever errors"!!!

 

3. Create a Function URL

Configuration -> Function URL

Then, the Function URL is generated and can be seen from the upper right corner. Copy it!

4. Create a test POST in Postman

Paste the Function URL in the POST URL area and then click the Savebutton.

Click the Send button, then the test results will be shown below.

5. Add information in Params, Headers, and Body

6. Modify the lambda_function and show details of "event"

Test the lambda_function from the test case of Postman. The return information is show as below.

The details of output are as follows.

{
    "event": {
        "headers": {
            "content-length": "59",
            "x-amzn-tls-version": "TLSv1.2",
            "x-forwarded-proto": "https",
            "postman-token": "0f337b21-f35a-4b63-9904-423aea79304a",
            "x-forwarded-port": "443",
            "x-forwarded-for": "54.86.50.139",
            "header_name": "Alex",
            "accept": "*/*",
            "header_country": "China",
            "x-amzn-tls-cipher-suite": "ECDHE-RSA-AES128-GCM-SHA256",
            "x-amzn-trace-id": "Root=1-65d3f694-5a37ccac4de9141818821224",
            "host": "as2yuw3zjpqcankr7k4eteumme0bmnbz.lambda-url.ap-southeast-2.on.aws",
            "content-type": "application/json",
            "cache-control": "no-cache",
            "accept-encoding": "gzip, deflate, br",
            "user-agent": "PostmanRuntime/7.36.3"
        },
        "isBase64Encoded": false,
        "rawPath": "/",
        "routeKey": "$default",
        "requestContext": {
            "accountId": "anonymous",
            "timeEpoch": 1708390036365,
            "routeKey": "$default",
            "stage": "$default",
            "domainPrefix": "as2yuw3zjpqcankr7k4eteumme0bmnbz",
            "requestId": "62ac7803-5d6b-4208-a8e9-c74647caa7a6",
            "domainName": "as2yuw3zjpqcankr7k4eteumme0bmnbz.lambda-url.ap-southeast-2.on.aws",
            "http": {
                "path": "/",
                "protocol": "HTTP/1.1",
                "method": "POST",
                "sourceIp": "54.86.50.139",
                "userAgent": "PostmanRuntime/7.36.3"
            },
            "time": "20/Feb/2024:00:47:16 +0000",
            "apiId": "as2yuw3zjpqcankr7k4eteumme0bmnbz"
        },
        "queryStringParameters": {
            "Param_Country": "China",
            "Param_Name": "Alex"
        },
        "body": "{\r\n    \"Body_Name\": \"Alex\",\r\n    \"Body_Country\": \"China\"\r\n}",
        "version": "2.0",
        "rawQueryString": "Param_Name=Alex&Param_Country=China"
    }
}

From the lambda_function, we can extract detail values. Specifically, for the key of body, the value of it is the type of string, we should convert it to the JSON format. Using json.loads() function can extract the JSON file from the string.

7. Extract specific values from "event"

 Get the values from the above JSON file in the lambda_function.

import json
 
def lambda_handler(event, context):
    return {
        # Headers
        "Header_Name": event["headers"]["header_name"],
        "Header_Country": event["headers"]["header_country"],
        
        # Params
        "Param_Name": event["queryStringParameters"]["Param_Name"],
        "Param_Country": event["queryStringParameters"]["Param_Country"],
        
        # Body
        "Body_Name": json.loads(event["body"])["Body_Name"],
        "Body_Country": json.loads(event["body"])["Body_Country"],
        
        # "POST" or "GET"
        "Type": event["requestContext"]["http"]["method"]
    }

It will shows like this.

{
    "Header_Name": "Alex",
    "Type": "POST",
    "Param_Country": "China",
    "Body_Country": "China",
    "Body_Name": "Alex",
    "Header_Country": "China",
    "Param_Name": "Alex"
}

8. Debug the codes in lambda_function

Monitor -> View CloudWatch logs -> Log groups -> Lambda Function Name -> Log streams

Using print() function to test the code and it will be printed in the log streams as follows.