feat: add prometheus metrics endpoint

.coveragerc

@@ -0,0 +1,3 @@
+[run]
+omit =
+    */wsgi.py

Dockerfile

@@ -17,6 +17,11 @@ FROM python:3.13-slim AS runtime
 
 WORKDIR /app
 ENV PYTHONUNBUFFERED=1
+ENV APP_MODE=start
+EXPOSE 8000
+
+COPY scripts/entrypoint.sh /app/entrypoint.sh
+RUN chmod +x /app/entrypoint.sh
 
 ARG APP_VERSION='undefined'
 ENV APP_VERSION=${APP_VERSION}
@@ -25,4 +30,4 @@ COPY --from=builder /build/dist/*.whl ./dist/
 
 RUN pip install ./dist/*.whl
 
-CMD ["start"]
+ENTRYPOINT ["/app/entrypoint.sh"]

README.md

@@ -63,6 +63,63 @@ docker run --rm -v /var/run/docker.sock:/var/run/docker.sock -ti glefer/docker-v
 docker run --rm -v /var/run/docker.sock:/var/run/docker.sock -ti glefer/docker-volumes-analyzer:0.1.0
 ```
 
+## Running the Application in Different Modes
+
+The application supports multiple modes of operation. You can specify the mode using the `APP_MODE` environment variable. The available modes are:
+
+- **CLI mode** (`start`): Runs the application in command-line interface mode.
+- **Web development mode** (`web`): Starts the application in web development mode.
+- **Gunicorn mode** (`gunicorn`): Runs the application using Gunicorn as the WSGI server.
+
+### Using Docker
+You can run the application in different modes by setting the `APP_MODE` environment variable when running the Docker container.
+
+#### CLI mode
+```bash
+docker run -e APP_MODE=start -v /var/run/docker.sock:/var/run/docker.sock glefer/docker-volumes-analyzer:latest
+```
+
+#### Web development mode
+```bash
+docker run -e APP_MODE=web -v /var/run/docker.sock:/var/run/docker.sock glefer/docker-volumes-analyzer:latest
+```
+
+#### Web production mode (gunicorn)
+```bash
+docker run -e APP_MODE=gunicorn -v /var/run/docker.sock:/var/run/docker.sock glefer/docker-volumes-analyzer:latest
+```
+
+### Using python locally
+If you prefer to run the application locally without Docker, you can use the entrypoint.sh script directly. Make sure you have all dependencies installed via Poetry.
+
+
+#### CLI mode
+```bash
+APP_MODE=start scripts/entrypoint.sh
+```
+
+#### Web development mode
+```bash
+APP_MODE=web scripts/entrypoint.sh
+```
+
+#### Web production mode (gunicorn)
+```bash
+APP_MODE=gunicorn scripts/entrypoint.sh
+```
+
+## Prometheus
+
+When running the application in **web** or **gunicorn** mode, it exposes a Prometheus metrics endpoint at `/metrics`. This endpoint provides detailed metrics about Docker volumes, such as:
+
+- Total number of Docker volumes.
+- Size of individual Docker volumes (in bytes).
+
+![Metrics](./doc/assets/metrics-endpoint.png)
+
+
+For more information about the metrics exposed and how to integrate them with Prometheus, refer to the [Prometheus documentation](./doc/prometheus.md).
+
 ---
 
 ## Run tests
@@ -88,7 +145,6 @@ poetry shell
 ```
 
 Formatting and checks:
-
 ```bash
 poetry run pre-commit run --all-files
 ```

doc/prometheus.md

@@ -0,0 +1,32 @@
+# Prometheus metrics endpoint
+The following metrics are exposed by the Prometheus metrics endpoint:
+
+- **`docker_volumes_total`**: The total number of Docker volumes currently available.
+    - **Type**: Gauge
+    - **Labels**: None
+    - **Example**: `docker_volumes_total 42`
+
+- **`docker_volume_size_bytes`**: The size of each Docker volume in bytes.
+    - **Type**: Gauge
+    - **Labels**:
+        - `volume`: The name of the Docker volume.
+    - **Example**: `docker_volume_size_bytes{volume="my_volume"} 104857600`
+
+## Accessing the Metrics Endpoint
+
+The Prometheus metrics are exposed at the `/metrics` endpoint. Depending on the mode in which the application is running, you can access the endpoint as follows:
+
+- **Web mode**: `http://<host>:8000/metrics`
+- **Gunicorn mode**: `http://<host>:8000/metrics`
+
+Replace `<host>` with the hostname or IP address where the application is running.
+
+## Integrating with Prometheus
+
+To scrape the metrics exposed by the application, add the following job configuration to your Prometheus configuration file (`prometheus.yml`):
+
+```yaml
+scrape_configs:
+  - job_name: "docker_volume_analyzer"
+    static_configs:
+      - targets: ["<host>:8000"]