# Serverless Weather App with AWS Lambda & HTTP API

## Overview
This project demonstrates how i built a **serverless application** to fetch real-time weather data using **AWS Lambda** and **API Gateway (HTTP API)**.
The app integrates with the **OpenWeatherMap API** and returns the current temperature and conditions for a given city.

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## Architecture
- **API Gateway (HTTP API)** → Provides a lightweight endpoint for client requests.
- **AWS Lambda (Python)** → Fetches weather data from OpenWeatherMap API.
- **OpenWeatherMap API** → External provider of weather information.
- **CloudWatch Logs** → For monitoring and debugging Lambda executions.

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## Steps Taken

### 1. Create AWS Lambda Function
- Wrote a **Python Lambda function** to query the OpenWeatherMap API.
- Used the `requests` library to make HTTP calls.
- Installed the requests library locally using `vscode`.
- Opened `vscode` and created a folder for the project (weather-app).
- Inside the folder open the terminal and run the following command: `python -m venv venv.`
- Activated the virtual environment on windows: `venv\scripts\activate.`
- Installed the requests library inside the virtual environment using: `pip install requests.`
- After installing requests, navigate to `venv\lib\site-packages.`
- Copied all the content and paste them into the weather app project folder: `xcopy requests \* C:\path\to\your\project-folder\ /E /I`
- Created a zip file containing all the content in the project folder.
- Upload to AWS Lambda.

- > **Note:** The Lambda code file is named `lambda_handler.py` (instead of the default `lambda_function.py`).
> The handler is defined as:
> ```
> lambda_handler.lambda_handler
> ```
> - First part → `lambda_handler` = the filename.
> - Second part → `lambda_handler` = the function name inside the file.
- ### 2. Set Up API Gateway HTTP API
- Created an **HTTP API** in API Gateway.
- Integrated the API with the Lambda function.
- Configured a route `/weather` with a query string parameter `city`.
- Deployed the API to a stage (e.g., `dev`).

### 3. Test the Application
- Called the API endpoint with:
- https://{api_id}.execute-api.us-east-1.amazonaws.com/weather?city=London

- Response returned the current **temperature** and **weather condition** for the city.

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## Verification
- Successfully retrieved weather data for multiple cities.
- Confirmed Lambda execution and debugging via **CloudWatch Logs**.

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## Key Learnings
- **AWS Lambda** allows building event-driven applications without managing servers.
- **HTTP APIs** are simpler and cheaper compared to REST APIs, making them great for lightweight services.
- Using **environment variables** ensures secure handling of API keys.

## Code Repository

🔗 GitHub Repo – https://github.com/samaj806/aws-weather-app.git