[SOLVED] Can an AWS Lambda Function Call Another Lambda Function? - amazon-web-services

[SOLVED] Can AWS Lambda Functions Invoke Each Other? A Simple Guide

In this chapter, we look at what AWS Lambda functions can do. We will see how they can call each other. It is important to know how to invoke one AWS Lambda function from another. This helps us build good serverless applications. In this article, we will talk about different ways to invoke Lambda functions. We will cover both synchronous and asynchronous calls. We will also mention best practices and IAM roles to keep our Lambda functions secure and working well together.

Here is what we will cover in this guide about AWS Lambda functions calling each other:

Part 1 - Using AWS SDK for Lambda Invocation: We will learn how to use the AWS SDK to invoke Lambda functions directly.
Part 2 - Configuring IAM Roles for Lambda Invocation: We will understand the permissions and IAM roles we need for Lambda-to-Lambda calls.
Part 3 - Synchronous vs Asynchronous Invocation: We will explore the differences between synchronous and asynchronous invocation methods.
Part 4 - Handling Responses from Invoked Lambda Functions: We will find out how to manage and process responses from our invoked Lambda functions.
Part 5 - Using Event Source Mapping for Chaining Lambdas: We will see how to use event source mapping to link Lambda functions.
Part 6 - Best Practices for Lambda Function Calls: We will review best practices to make our Lambda invocations better and more secure.
Frequently Asked Questions: We will answer common questions about AWS Lambda function invocations.

For more reading on AWS topics, you can check our guides on how to configure access control and how to fix authorization issues. Now let’s get into the details of invoking AWS Lambda functions from each other!

Part 1 - Using AWS SDK for Lambda Invocation

We can invoke another AWS Lambda function from a Lambda function using the AWS SDK for JavaScript (Node.js). This lets us make both synchronous and asynchronous calls.

Step 1: Set Up AWS SDK

We need to make sure that the AWS SDK is in our Lambda function. If we are using Node.js, it is built-in. So we don’t need to install it separately.

Step 2: Invoke Another Lambda Function

Here is a simple code snippet that shows how to invoke another Lambda function using the AWS SDK:

const AWS = require("aws-sdk");
const lambda = new AWS.Lambda();

exports.handler = async (event) => {
  const params = {
    FunctionName: "YourOtherLambdaFunctionName", // Change to your Lambda function name
    InvocationType: "RequestResponse", // Use for synchronous invocation
    Payload: JSON.stringify(event), // Send the event to the invoked function
  };

  try {
    const response = await lambda.invoke(params).promise();
    console.log(
      "Response from invoked function:",
      JSON.parse(response.Payload),
    );
    return response;
  } catch (err) {
    console.error("Error invoking Lambda function:", err);
    throw err;
  }
};

Key Points:

FunctionName: We need to provide the name of the Lambda function we want to invoke.
InvocationType: We can use RequestResponse for synchronous calls or Event for asynchronous calls.
Payload: We should pass the input data to the invoked function.

For more information on AWS Lambda invocation methods, we can check the AWS Lambda documentation.

We also need to ensure that the Lambda function calling has the right permissions (IAM role policies) to invoke the target Lambda function. We will talk about this in the next part.

For more insights on AWS Lambda features, we can look at how to configure access control.

Part 2 - Configuring IAM Roles for Lambda Invocation

To let one AWS Lambda function call another, we need to set up the right IAM roles and permissions. This means we create an IAM role that gives the needed permissions. Then we attach that role to the Lambda function that will do the invoking.

Create an IAM Role for Lambda Invocation:
- First, go to the IAM console in the AWS Management Console.
- Click on Roles and then choose Create role.
- Select AWS Service as the trusted entity and pick Lambda.
- Click Next: Permissions.

Attach the AWSLambdaRole Policy:

Look for the AWSLambdaRole policy or make a custom policy with these permissions:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": "lambda:InvokeFunction",
      "Resource": "arn:aws:lambda:<region>:<account-id>:function:<function-name>"
    }
  ]
}

Change <region>, <account-id>, and <function-name> to your real AWS region, account ID, and the name of the Lambda function you want to call.

Attach the Role to Your Lambda Function:
- Go to the Lambda console.
- Choose the Lambda function that will call another Lambda function.
- In the Configuration tab, click on Permissions.
- Under Execution role, click Edit and pick the role we just created.
Verify the Role Permissions:
- Make sure the role has the right permissions to call the target Lambda function. We can test this using the AWS SDK or AWS CLI.

Example of Invoking a Lambda Function: Here is a simple example to call another Lambda function using AWS SDK for Python (Boto3):

import boto3

client = boto3.client('lambda')

response = client.invoke(
    FunctionName='target_lambda_function_name',
    InvocationType='RequestResponse',  # For synchronous
    Payload=b'{}'  # Input payload
)

print(response['Payload'].read())

This code shows how to call a Lambda function named target_lambda_function_name.

For more details about AWS Lambda permissions, look at the official AWS documentation. If we need more info on IAM roles or permissions, we can check out how can AWS Lambda function invoke another Lambda.

Part 3 - Synchronous vs Asynchronous Invocation

AWS Lambda functions can be called in two ways. We can use synchronous or asynchronous invocation. Each method is good for different situations.

Synchronous Invocation

With synchronous invocation, we wait for the function to finish its work. Then it gives us a response. This is helpful when we need quick feedback.

Code Example (Node.js):

const AWS = require("aws-sdk");
const lambda = new AWS.Lambda();

const params = {
  FunctionName: "YourLambdaFunctionName",
  Payload: JSON.stringify({ key: "value" }),
};

lambda.invoke(params, (error, data) => {
  if (error) {
    console.error("Error invoking Lambda:", error);
  } else {
    console.log("Lambda response:", JSON.parse(data.Payload));
  }
});

Asynchronous Invocation

Asynchronous invocation lets us send an event to the Lambda function. We do not wait for a response. This is good for tasks that do not need an immediate answer.

Code Example (Node.js):

const AWS = require("aws-sdk");
const lambda = new AWS.Lambda();

const params = {
  FunctionName: "YourLambdaFunctionName",
  InvocationType: "Event", // Use 'Event' for async invocation
  Payload: JSON.stringify({ key: "value" }),
};

lambda.invoke(params, (error, data) => {
  if (error) {
    console.error("Error invoking Lambda asynchronously:", error);
  } else {
    console.log("Lambda async invocation response:", data);
  }
});

Key Differences

Response Handling: In synchronous invocation, we must handle the response. Asynchronous invocation does not need this.
Use Cases: We use synchronous invocation for API calls. We use asynchronous invocation for background tasks or workflows that are event-driven.

For more info on AWS Lambda function invocation strategies, check this guide on AWS Lambda.

Part 4 - Handling Responses from Invoked Lambda Functions

When we use an AWS Lambda function to call another Lambda function, we need to handle the responses well. This helps us make sure everything works smoothly. Here is how we can manage responses based on the type of invocation.

Synchronous Invocation

With synchronous invocations, the calling function waits for the response. We can get the response right in the code.

Here is an example using AWS SDK for JavaScript:

const AWS = require("aws-sdk");
const lambda = new AWS.Lambda();

const params = {
  FunctionName: "YourTargetLambdaFunction",
  Payload: JSON.stringify({ key: "value" }),
};

lambda.invoke(params, (error, data) => {
  if (error) {
    console.error("Error invoking Lambda function:", error);
  } else {
    const response = JSON.parse(data.Payload);
    console.log("Response from invoked Lambda function:", response);
  }
});

Asynchronous Invocation

For asynchronous invocations, the calling function does not wait for the response. In this case, we can manage the response using a callback method or a logging system to track it.

Here is an example using AWS SDK for Python (boto3):

import boto3

lambda_client = boto3.client('lambda')

response = lambda_client.invoke(
    FunctionName='YourTargetLambdaFunction',
    InvocationType='Event',  # Asynchronous invocation
    Payload=json.dumps({'key': 'value'})
)

print("Invocation sent to the Lambda function, no response is awaited.")

Error Handling

No matter what type of invocation we use, we should handle errors. For synchronous invocations, we check the StatusCode in the response. For asynchronous invocations, we can add Dead Letter Queues (DLQs) to catch any failed events.

Example of Handling Errors

if (data.StatusCode !== 200) {
  console.error("Error from invoked Lambda function:", data.FunctionError);
}

By following these steps, we can manage responses from invoked Lambda functions well. This helps us make strong and reliable Lambda-based applications. If we want to learn more about advanced settings, we can look into how to configure access control for our Lambda functions.

Part 5 - Using Event Source Mapping for Chaining Lambdas

We can chain AWS Lambda functions by using event source mapping. We can use services like Amazon SQS (Simple Queue Service) or DynamoDB Streams. This way, one Lambda function can start based on events from another. It helps us create a good workflow.

Using Amazon SQS

Create an SQS Queue: First, we need to set up an SQS queue. The first Lambda function will send messages to this queue.

Configure the First Lambda Function: In the first Lambda function, we will use the AWS SDK to send messages to SQS.

import json
import boto3

sqs = boto3.client('sqs')
queue_url = 'https://sqs.<region>.amazonaws.com/<account-id>/<queue-name>'

def lambda_handler(event, context):
    message = {
        'key1': 'value1',
        'key2': 'value2'
    }

    response = sqs.send_message(
        QueueUrl=queue_url,
        MessageBody=json.dumps(message)
    )
    return response

Create the Second Lambda Function: Now, we create the second Lambda function. This function will handle messages from the SQS queue.

Configure Event Source Mapping: In the AWS Console, we set the second Lambda function to trigger on the SQS queue. We can also do this using AWS CLI:

aws lambda create-event-source-mapping \
    --function-name <SecondLambdaFunction> \
    --batch-size 10 \
    --event-source-arn arn:aws:sqs:<region>:<account-id>:<queue-name>

Using DynamoDB Streams

Enable DynamoDB Streams: For our DynamoDB table, we need to enable streams. This will capture changes at the item level.

Configure the First Lambda Function: We will insert data into the DynamoDB table from this function.

import boto3

dynamodb = boto3.resource('dynamodb')
table = dynamodb.Table('<your-table-name>')

def lambda_handler(event, context):
    response = table.put_item(
        Item={
            'PrimaryKey': 'key1',
            'Attribute': 'value'
        }
    )
    return response

Create the Second Lambda Function: This function will be triggered by the DynamoDB stream.

Configure Event Source Mapping: We can set this up in the AWS Console or use the CLI.

aws lambda create-event-source-mapping \
    --function-name <SecondLambdaFunction> \
    --batch-size 5 \
    --event-source-arn arn:aws:dynamodb:<region>:<account-id>:table/<your-table-name>/stream/NEW_AND_OLD_IMAGES

By using event source mapping with SQS or DynamoDB Streams, we can chain Lambda functions. This way, we create scalable and separate architectures. For more information, we can check these links: AWS Lambda Function Invocation and Configuring Access Control.

Part 6 - Best Practices for Lambda Function Calls

When we call an AWS Lambda function from another Lambda function, we need to follow some best practices. This helps us to make sure our operations are good and safe. Here are some important tips:

Use AWS SDK for Invocation: We should always use the AWS SDK to call other Lambda functions. This helps our calls to work better. For example, in Python with Boto3:

import boto3

lambda_client = boto3.client('lambda')

response = lambda_client.invoke(
    FunctionName='YourSecondLambdaFunction',
    InvocationType='RequestResponse',  # or 'Event' for async
    Payload=json.dumps({'key': 'value'})
)

Manage IAM Roles and Permissions: We need to make sure the Lambda function that calls another function has the right IAM permissions. We can attach a policy like this to the Lambda role:
```
{
  "Effect": "Allow",
  "Action": "lambda:InvokeFunction",
  "Resource": "arn:aws:lambda:region:account-id:function:YourSecondLambdaFunction"
}
```
Monitor and Optimize Performance: We can use AWS CloudWatch to check how our Lambda functions are doing. We should set up alerts for errors and high delays. This helps us to fix problems early.

Handle Errors Gracefully: We must add error handling in our Lambda functions. This helps us to deal with failed calls. We can use try-except blocks to catch problems and log them for fixing later.

try:
    response = lambda_client.invoke(
        FunctionName='YourSecondLambdaFunction',
        Payload=json.dumps({'key': 'value'})
    )
except Exception as e:
    print(f"Error invoking function: {e}")

Use Asynchronous Invocation When Appropriate: For tasks that take a long time and do not need quick results, we should use async invocation. This makes our performance better and cuts down delays.
Limit Payload Size: We need to know the limits on payload size (6 MB for synchronous and 256 KB for async). We should make sure our data stays within these limits.
Consider Event Source Mapping for Scalability: If we want to link Lambda functions together, we can use Event Source Mapping. This lets us trigger one function from another based on events and helps with scaling.
Implement Retries and Dead Letter Queues (DLQ): For async calls, we should set up a DLQ (SQS or SNS) to handle failed calls. This way, we do not lose events if the target function has problems.
Test Locally: We can use tools like SAM CLI to test our Lambda function on our computer before putting it on AWS. This helps us find errors early.
Keep Functions Small and Focused: We should design each Lambda function to do one task or a few related tasks. This helps us to maintain our code better and makes debugging easier.

By following these best practices for AWS Lambda function calls, we can make sure our functions work well, are safe, and are reliable. For more info on optimizing AWS services, visit this guide on AWS Lambda function invocation.

Frequently Asked Questions

1. Can an AWS Lambda function call another Lambda function directly?

Yes, an AWS Lambda function can call another Lambda function directly. We can use the AWS SDK for this. This helps us create a modular system. Functions can do specific tasks. This makes our code easier to reuse and maintain. If you want to know how to call another Lambda function, check our guide on how can AWS Lambda function invoke another function.

2. How do I set up IAM roles for Lambda invocation?

To let one AWS Lambda function call another, we have to set up IAM roles. First, we need to create an IAM role with the right permissions. Then we attach it to the Lambda function that is calling. This way, the calling function can invoke the other function safely. For more details on IAM roles, visit our article on how to configure access control.

3. What is the difference between synchronous and asynchronous invocation in AWS Lambda?

In AWS Lambda, synchronous invocation means the calling function waits for a response from the invoked function. Asynchronous invocation lets the calling function keep running without waiting. We should understand this difference. It helps us make our Lambda functions perform better. For more info on invocation types, check our section on synchronous vs asynchronous invocation.

4. How can I handle responses from invoked Lambda functions?

When we invoke another AWS Lambda function, we can handle the response using the AWS SDK. If we invoke it synchronously, we can process the response right away. For asynchronous calls, we do not get the response back. So we might need to use an event-driven setup to manage the results. You can learn more about this in our guide on managing Lambda responses.

5. What are the best practices for calling one Lambda function from another?

When we call AWS Lambda functions, it is good to reduce latency. We should keep our functions lightweight, use asynchronous invocations when we can, and have error handling ready. Also, we must make sure IAM roles are set up right to avoid permission problems. For more tips on optimizing your Lambda function calls, check our section on best practices for Lambda function calls.

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[SOLVED] Can an AWS Lambda Function Call Another Lambda Function? - amazon-web-services

[SOLVED] Can AWS Lambda Functions Invoke Each Other? A Simple Guide

Part 1 - Using AWS SDK for Lambda Invocation

Step 1: Set Up AWS SDK

Step 2: Invoke Another Lambda Function

Key Points:

Part 2 - Configuring IAM Roles for Lambda Invocation

Part 3 - Synchronous vs Asynchronous Invocation

Synchronous Invocation

Asynchronous Invocation

Key Differences

Part 4 - Handling Responses from Invoked Lambda Functions

Synchronous Invocation

Asynchronous Invocation

Error Handling

Example of Handling Errors

Part 5 - Using Event Source Mapping for Chaining Lambdas

Using Amazon SQS

Using DynamoDB Streams

Part 6 - Best Practices for Lambda Function Calls

Frequently Asked Questions

1. Can an AWS Lambda function call another Lambda function directly?

2. How do I set up IAM roles for Lambda invocation?

3. What is the difference between synchronous and asynchronous invocation in AWS Lambda?

4. How can I handle responses from invoked Lambda functions?

5. What are the best practices for calling one Lambda function from another?

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