# MQTT Consumer

The **MQTT (Message Queuing Telemetry Transport) Consumer** is a lightweight, publish-subscribe client designed to consume messages from an **MQTT broker**.

It is optimized for environments with **low bandwidth, high latency, or resource-constrained devices**, making it widely used in **Internet of Things (IoT)** applications.

The component subscribes to defined MQTT topics and consumes messages with configurable Quality of Service (QoS) levels.

### Configuration Sections

All configurations are classified into the following sections:

* **Basic Information**
* **Meta Information**
* **Resource Configuration**
* **Connection Validation**

### Basic Information Tab

The *Basic Information* tab defines general execution settings.

| Field                       | Description                                                               | Required |
| --------------------------- | ------------------------------------------------------------------------- | -------- |
| **Invocation Type**         | Select execution mode: **Batch** or **Real-Time**.                        | Yes      |
| **Deployment Type**         | Displays the deployment type of the component (pre-selected).             | Yes      |
| **Container Image Version** | Displays the Docker image version used (pre-selected).                    | Yes      |
| **Failover Event**          | Select a failover event to handle retries or errors.                      | Optional |
| **Batch Size**              | Maximum number of records processed in one execution cycle (minimum: 10). | Yes      |

### Meta Information Tab

The *Meta Information* tab configures the MQTT broker connection, authentication, and topic subscription.

| Field                        | Description                                                                                               | Required    |
| ---------------------------- | --------------------------------------------------------------------------------------------------------- | ----------- |
| **Host IP Address**          | IP address of the MQTT broker.                                                                            | Yes         |
| **Username**                 | Username for authentication.                                                                              | Conditional |
| **Port**                     | Port of the MQTT broker (default: **1883** for non-SSL, **8883** for SSL).                                | Yes         |
| **Authenticator**            | Authentication method: **Password** or **PEM/PPK File**.                                                  | Yes         |
| **Password**                 | Password for authentication (used if *Password* method is selected).                                      | Conditional |
| **PEM/PPK File**             | Upload PEM/PPK key file for secure authentication (if selected).                                          | Conditional |
| **Quality of Service (QoS)** | Defines message delivery guarantee: **0 (At most once)**, **1 (At least once)**, or **2 (Exactly once)**. | Yes         |
| **MQTT Topic**               | Name of the topic from which to consume published messages.                                               | Yes         |

### Quality of Service (QoS) Levels

The MQTT Consumer supports three **QoS levels**, which define delivery guarantees between broker and client:

| QoS Level             | Delivery Guarantee                       | Description                                                                  |
| --------------------- | ---------------------------------------- | ---------------------------------------------------------------------------- |
| **0 – At most once**  | Best-effort delivery, no acknowledgment. | Messages may be lost if the connection fails.                                |
| **1 – At least once** | Guaranteed delivery **≥1 time**.         | Messages are re-sent until acknowledgment is received. Duplicates may occur. |
| **2 – Exactly once**  | Guaranteed delivery **only once**.       | Highest reliability, but slower due to 4-step handshake.                     |

### Workflow Steps

To run a pipeline workflow with the MQTT Consumer:

1. Drag and drop the **MQTT Consumer** component into the **Pipeline Workflow Editor**.
2. Configure the **Basic Information** and **Meta Information** tabs.
3. Click **Save Component** (Storage icon).
4. Update and activate the **Pipeline Workflow**.
5. Monitor activity in the **Logs panel** to verify message consumption when the pipeline starts.

### Example Workflow

1. Connect the MQTT Consumer to a broker running at `192.168.1.20` on port `1883`.
2. Set **QoS** to `1 (At least once)` for reliable delivery.
3. Subscribe to the topic `iot/sensors/temperature`.
4. When the pipeline runs, the consumer retrieves temperature readings published by IoT devices and forwards them to downstream events for analysis.


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