# Join Each

### Overview

The **JoinEach Component** is designed to work with the **Each Component**. It collects multiple incoming messages based on a specified count and outputs them as a single batch when all expected messages have arrived. If some messages do not arrive within a timeout period, it outputs the partial batch along with count information.

### Usage

#### Input Ports

| Port    | Description                                                                                  |
| ------- | -------------------------------------------------------------------------------------------- |
| `in`    | Receives individual messages to be aggregated. Each message must contain a `correlationId`.  |
| `count` | Specifies the total number of messages expected. Must be provided before aggregation begins. |

#### Output Ports

| Port      | Description                                                                                                    |
| --------- | -------------------------------------------------------------------------------------------------------------- |
| `out`     | Fires when all expected messages arrive, emitting an array of collected messages.                              |
| `timeout` | Fires when the timeout is reached before all expected messages arrive, providing the partial batch and counts. |

#### Output Data for `out` Port

| Field   | Description                      |
| ------- | -------------------------------- |
| `items` | The array of collected messages. |

#### Output Data for `timeout` Port

| Field     | Description                                            |
| --------- | ------------------------------------------------------ |
| `items`   | The array of messages that arrived before the timeout. |
| `count`   | The number of expected messages.                       |
| `arrived` | The number of messages that actually arrived.          |

### Instructions

1. **Set Up with Each Component**
   * Ensure messages sent to `in` contain a `correlationId` matching the one from the **Each** component.
2. **Define Expected Count**
   * Send a message to the `count` port specifying how many messages the component should wait for.
3. **Processing Messages**
   * The component collects messages based on the `correlationId`.
   * When all expected messages arrive, they are sent as an array to the `out` port.
   * If not all messages arrive before the timeout, the `timeout` port emits the partial batch.

### Notes

* **Works with Correlation IDs**: Ensures messages from the same batch are correctly joined.
* **Timeout Handling**: Prevents indefinite waiting if some messages fail to arrive.
* **Batch Processing**: Useful for grouping messages into structured outputs for further processing.