How can I connect Oracle DB to lambda using the oracledb python module?

Question

Our Oracle database , with version 12.1, is hosted on ec2 as a standalone DB. I am trying to access that server from another account. Using the python module oracleDB in Thin Mode, I wrote a script that allows me to connect to the database.

From my local system, using Visual Studio, I am able to connect to the database. However, when I modify the same code to AWS Lambda and test it, my lambda function times out.

I tried to modify the VPC setting of the database. I set the lambda function as part of an inbound rule and for lambda iam role I provided 'AWSLambdaVPCAccessExecutionRole'.

Could someone explain why is it happening and how I could fix it?

Here is the error message I get:

{
    "errorMessage": "2023-11-29T17:33:43.835Z 7bb3a696-cab2-4964-9a09-691995e136f1 Task timed out after 30.01 seconds"
}

Below is the code implementation:

import oracledb
import csv
import os
from datetime import datetime
import boto3
import json


def lambda_handler(event, context):
    try:
        export_to_csv("Sample")
        return {"statusCode": 200, "body": json.dumps("Hello from Lambda!")}

    except Exception as e:
        print(f"Error: {str(e)}")
        return {"statusCode": 500, "body": json.dumps(f"Error: {str(e)}")}

def export_to_csv(table_name):
    try:
        # Initialize Oracle client
        # Oracle connection details
        oracle_user = "***"
        oracle_password = "****"
        oracle_dsn = "****"

        s3_bucket_name = "***"
        s3_prefix = "****"
        aws_access_key = "****"
        aws_secret_key = "****"

        # Initialize Oracle connection
        connection = oracledb.connect(
            user=oracle_user, password=oracle_password, dsn=oracle_dsn
        )

        # Create an S3 client
        s3_client = boto3.client(
            "s3", aws_access_key_id=aws_access_key, aws_secret_access_key=aws_secret_key
        )

        if connection:
            # Query to get column names
            cursor = connection.cursor()
            cursor.execute(
                f"SELECT COLUMN_NAME FROM ALL_TAB_COLUMNS WHERE TABLE_NAME = '{table_name}'"
            )
            column_names = [row[0] for row in cursor.fetchall()]

            # Get current date
            current_date = datetime.now().strftime("%Y%m%d_%H%M%S")

            # Define CSV file path with current date in the filename
            csv_file_path = f"output_{current_date}.csv"

            with open(csv_file_path, "w", newline="") as csv_file:
                csv_writer = csv.writer(csv_file)

                csv_writer.writerow(column_names)
                cursor.execute(f"SELECT * FROM {table_name} ")
                data = cursor.fetchall()

                # Write data rows
                for row in data:
                    csv_writer.writerow(row)

            # Upload CSV file to S3
            s3_object_key = os.path.join(s3_prefix, f"output_{current_date}.csv")
            s3_client.upload_file(csv_file_path, s3_bucket_name, s3_object_key)

            print("Data transfer to S3 completed")

        else:
            raise Exception("Oracle connection failed.")

    except Exception as e:
        print(f"Error is {e}")
        raise e