> For the complete documentation index, see [llms.txt](https://docs.appmixer.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.appmixer.com/connector-configuration/utils/test/join.md).

# Join

### Overview

The **Join Component** merges messages from the `join` port with each message on the `in` port, ensuring that data from both sources is combined before proceeding in the workflow.

### Usage

This component is useful for synchronizing data streams, allowing separate inputs to be merged into a single structured message.

#### Input Ports

| Port   | Description                                                                          |
| ------ | ------------------------------------------------------------------------------------ |
| `join` | Receives a message that will be attached to every message arriving on the `in` port. |
| `in`   | Receives primary input messages that will be merged with the `join` message.         |

#### Output Ports

| Port  | Description                                                 |
| ----- | ----------------------------------------------------------- |
| `out` | Sends merged messages combining data from both input ports. |

#### Processing Logic

1. **Receives Join Message**: Stores the message received on the `join` port.
2. **Queues Incoming Messages**: Messages from the `in` port are queued until a `join` message is available.
3. **Merges Data**: Once both inputs are received, messages are combined and sent to the `out` port.
4. **Respects Execution Order**: Ensures `join` data is only applied to messages from the current test execution.

### Notes

* **Ensures Data Synchronization**: Prevents messages from being processed until a `join` message is received.
* **Supports Test Automation**: Works alongside `BeforeAll` and `AfterAll` to maintain test flow consistency.
* **Efficient Message Processing**: Queues and batches messages for optimal execution.

This component is essential for workflows requiring data synchronization across multiple input streams before further processing.


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