> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/gsampallo/MQTTGateway/llms.txt
> Use this file to discover all available pages before exploring further.

# Environment variables

> Configure MQTT Gateway using environment variables for database connections, MQTT settings, and operational parameters

MQTT Gateway is configured through environment variables defined in a `.env` file. All settings are loaded at startup from the environment.

## Configuration file

Create a `.env` file in the root directory of the project. You can use `.env.example` as a template:

```bash theme={null}
cp .env.example .env
```

## Database connection

<ParamField path="DB_HOST" type="string" required>
  Database server hostname or IP address.

  Example: `192.168.0.137`
</ParamField>

<ParamField path="DB_PORT" type="integer" default="3306">
  Database server port number.

  Example: `3306`
</ParamField>

<ParamField path="DB_NAME" type="string" required>
  Name of the database to connect to.

  Example: `db`
</ParamField>

<ParamField path="DB_USER" type="string" required>
  Database username for authentication.

  Example: `demo`
</ParamField>

<ParamField path="DB_PASSWORD" type="string" required>
  Database password for authentication.

  Example: `demo`
</ParamField>

<Note>
  The gateway uses these credentials to build a SQLAlchemy connection URL in the format:
  `mysql+pymysql://{DB_USER}:{DB_PASSWORD}@{DB_HOST}:{DB_PORT}/{DB_NAME}`
</Note>

## MQTT settings

<ParamField path="MQTT_CLIENT_ID" type="string" default="mqtt-gateway">
  Unique identifier for the MQTT client connection. This ID is used when connecting to the MQTT broker.

  Example: `mqtt-gateway`
</ParamField>

<ParamField path="MQTT_KEEPALIVE" type="integer" default="60">
  MQTT keepalive interval in seconds. The client will send ping messages to the broker at this interval to maintain the connection.

  Example: `60`
</ParamField>

## Operational settings

<ParamField path="LOG_DIR" type="string" default="./log">
  Directory path where log files will be written.

  Example: `./log`
</ParamField>

<ParamField path="HTTP_TIMEOUT_SECONDS" type="integer" default="10">
  Timeout in seconds for HTTP requests when forwarding messages to HTTP endpoints.

  Example: `10`
</ParamField>

<ParamField path="FLOWS_RELOAD_INTERVAL_SECONDS" type="integer" default="600">
  Interval in seconds between automatic reloads of flow configurations from the database. This allows the gateway to pick up configuration changes without restarting.

  Minimum value: `1`

  Example: `600` (10 minutes)
</ParamField>

## Example configuration

```bash theme={null}
# Database connection
DB_HOST=192.168.0.137
DB_PORT=3306
DB_NAME=db
DB_USER=demo
DB_PASSWORD=demo

# Logging
LOG_DIR=./log

# HTTP settings
HTTP_TIMEOUT_SECONDS=10

# MQTT settings
MQTT_CLIENT_ID=mqtt-gateway
MQTT_KEEPALIVE=60

# Flow configuration
FLOWS_RELOAD_INTERVAL_SECONDS=600
```

<Warning>
  Ensure that required environment variables (`DB_HOST`, `DB_NAME`, `DB_USER`, `DB_PASSWORD`) are set before starting the gateway. Missing required variables will cause the application to fail at startup.
</Warning>