Deploying Lambda function: listCollectionFunction

Overview

This page describes how to create the listCollectionFunction Lambda function.
It is used to retrieve the list of all faces currently stored in your Amazon Rekognition collection.

Step 1: Create the Lambda function

  1. In the Lambda console, navigate to Functions.

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  1. Choose Create function.

  2. Under Author from scratch:

    • Function name: listCollectionFunction
    • Runtime: Node.js 22.x
    • Architecture: x86_64

Other Additional configurations can be left alone.

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  1. Choose Create function.

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Step 2: Add the function code

  1. In the Code tab, replace the default code with the handler from your Amplify project:

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Or copy the handler.js file from:
Amplify/functions/listCollectionFunction/handler.js

import {
  ListFacesCommand,
  RekognitionClient,
} from "@aws-sdk/client-rekognition";

const clientConfig = {
  region: process.env.AWS_REGION || "us-east-1",
  credentials: {
    accessKeyId: process.env.AWS_ACCESS_KEY_ID,
    secretAccessKey: process.env.AWS_SECRET_ACCESS_KEY,
  },
};

const rekognitionClient = new RekognitionClient(clientConfig);

class RekognitionService {
  static async listFaces(collectionId, maxResults = 100, nextToken = null) {
    const command = new ListFacesCommand({
      CollectionId: collectionId,
      MaxResults: maxResults,
      ...(nextToken && { NextToken: nextToken }),
    });

    return await rekognitionClient.send(command);
  }
}

export const handler = async (event) => {
  try {
    const faces = [];
    let result = await RekognitionService.listFaces(
      process.env.REKOGNITION_COLLECTION,
      100
    );

    faces.push(...result.Faces);

    while (result.NextToken) {
      result = await RekognitionService.listFaces(
        process.env.REKOGNITION_COLLECTION,
        100,
        result.NextToken
      );
      faces.push(...result.Faces);
    }

    console.log(faces);

    const processed = faces.map((face) => ({
      FaceId: face.FaceId,
      ExternalImageId: face.ExternalImageId,
      s3Key: `faces/${face.ExternalImageId}.jpg`,
    }));

    return {
      statusCode: 200,
      headers: {
        "Content-Type": "application/json",
        "Access-Control-Allow-Origin": "*", // nếu cần CORS
      },
      body: JSON.stringify({ success: true, faces: processed }),
    };
  } catch (err) {
    console.error("Error listing collections:", err);
    return {
      statusCode: 500,
      headers: {
        "Content-Type": "application/json",
        "Access-Control-Allow-Origin": "*",
      },
      body: JSON.stringify({ success: false, error: err.message }),
    };
  }
};

Choose Deploy (or Ctrl + Shift + U) to save your changes.

Step 3: Configure environment variables

  1. In the Configuration tab, choose Environment variables.

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  1. Add the following:
S3_BUCKET=YOUR_S3_BUCKET_NAME
REKOGNITION_COLLECTION=YOUR_REKOGNITION_COLLECTION_NAME
DYNAMO_TABLE=YOUR_DYNAMO_TABLE_NAME

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  1. Save changes.

Step 4: Assign IAM permissions

Your Lambda function needs permission to list all faces from your Rekognition collection.

  1. In the Configuration tab, go to Permissions and click the role name attached to your Lambda function.

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  1. In IAM, choose Add permissions → Create inline policy.

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  1. Switch to JSON view and paste:
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": "rekognition:ListFaces",
      "Resource": "*"
    }
  ]
}

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  1. Save the policy and attach it to your Lambda execution role.

At this point, listCollectionFunction is ready to be used to query all faces in your Rekognition collection.