# Quick Start: Create a Flow Using Gemini Node This section demonstrates how to quickly create and test an LLM-based Flow in the Flow Designer through a practical use case using the Gemini Node. This example demonstrates how to build a Flow that integrates with the Gemini LLM to process MQTT device messages using dynamic input context, such as `clientid` and `payload.type`, by constructing a natural language prompt from multiple parameters. It breaks the limitation of single-field LLM input, enabling more flexible and context-aware AI processing. The workflow receives command-type messages from devices, generates a formatted response via the LLM, and republishes the result to a client-specific topic for further handling. ## Scenario Description Assume a device reports a command request to the MQTT topic `commands/inbox/`. Each message includes a command type, such as `restart`, in JSON format. The EMQX Flow will perform the following steps: - **Data Processing**: Build a prompt that includes the client ID and requested command type contained in the message payload. - **LLM-Based Processing**: Use a Gemini-compatible model to generate an action instruction based on the request. - **Message Republish**: Publish the AI-generated result to a topic such as `device//command`. **Sample message:** ```json { "type": "restart" } ``` **Expected output (AI-generated):** ```css action:restart;client:clientid ``` ## Create the Flow ::: tip Prerequisite Make sure you have a valid Gemini API Key. ::: 1. Click the **Create Flow** button on the **Flows** page. 2. Add a **Messages** node. - Drag a **Messages** node from the Source panel. - Set the topic to `commands/inbox/+`. - Click **Save**. 3. Add a **Data Processing** node. - Drag a **Data Processing** node from the **Processing** section. - Fill in the transformation form with the following configurations. These transformations construct a readable natural language prompt that includes the MQTT client ID and the requested action type that will be contained in the message payload. This prompt will be sent to the Gemini LLM for processing. - Concatenate `Client ` and `clientid` into a base string. Creates the beginning of the prompt by identifying the client. - **Field**: `clientid` - **Transform**: Select `String Functions` -> `concat` - **Alias**: `base` - **String1**: `Client ` (include a space after the word) - **String2**: `clientid` - Concatenate `base` and `requested ` into `base2`. Adds the verb to indicate the action being requested. - **Field**: `base` - **Transform**: `concat` - **Alias**: `base2` - **String1**: `base` - **String2**: ` requested ` (include a space before and after the word) - Concatenate `base2` and `payload.type` into `prompt`. Completes the full sentence for the LLM prompt. - **Field**: `base2` - **Transform**: `concat` - **Alias**: `prompt` - **String1**: `base2` - **String2**: `payload.type` ::: tip Example prompt result If a client with ID `device123` sends a message with payload `{ "type": "restart" }`, the resulting prompt will be: ``` Client device123 requested restart ``` ::: - Expose `clientid` for later use to ensures that it is accessible in downstream nodes (e.g., for `${clientid}` in republish topics). - **Field**: `clientid` - **Transform**: Leave empty - **Alias**: `clientid` - Click **Switch to SQL**. You should see a SQL expression similar to: ```sql concat('Client ', clientid) as base, concat(base, ' requested ') as base2, concat(base2, payload.type) as prompt, clientid as clientid ``` ::: tip The `clientid` and `payload.type` should not be wrapped in quotes or treated as string literals. They are field references, and quoting them would cause the rule to treat them as plain text instead of extracting their actual values from the message. ::: - Click **Save**. 4. Add a **Gemini** node. - Drag a **Gemini** node from the Processing section and connect it to the Data Processing node. - Configure the node: - **Input**: Enter `prompt`. - **System Message**: Enter the following message: ``` You are a device command formatter. Generate a short command in this format: action:;client: Only return a single line, no Markdown or extra formatting. ``` - **Model**: Here you can keep the default model `gemini-2.0-flash`. - **API Key**: Enter your Gemini API key. - **Base URL**: Leave empty to use Gemini’s default endpoint. - **Output Result Alias**: Enter `ai_reply`. - Click **Save**. 5. Add a **Republish** node. - Drag a **Republish** node from the Sink section and connect it to the Gemini node. - Set the topic to `device/${clientid}/command`. - Set the payload to `${ai_reply}`. - Click **Save**. 6. Connect all the nodes and click **Save** in the upper-right corner to save the Flow. ![openai_node_flow](./assets/gemini_node_flow.png) Flows and form rules are interoperable. You can also view the SQL and related rule configurations on the Rule page. ![openai_node_rule_page](./assets/gemini_node_rule_page.png) ## Test the Flow 1. Connect an MQTT client to EMQX. To quickly test the flow, you can use the **Diagnostic Tools** -> **WebSocket Client** on the Dashboard to simulate an MQTT client. Alternatively, you can also use the [MQTTX](https://mqttx.app/) tool or a real MQTT client: - Connect to your EMQX server. - Subscribe to the topic, for example `device/c_emqx/command`. 2. Start Testing. - In the Flow Designer, click any node to open the Edit panel. - Click **Edit**, then click **Start Test** to open the test panel at the bottom. - Click **Input Simulated Data** and publish this message to topic `commands/inbox/c_emqx` by clicking **Submit Test**: ```json { "type": "restart" } ``` 3. Review results. - You can see the successful execution result of the flow. ![openai_node_test_result](./assets/gemini_node_test_result.png) - Return to the **WebSocket Client** page and you should receive an AI-generated summary like: > “action:restart;client:c_emqx” - If the test results are unsuccessful, error messages will be displayed accordingly. - To view the running statistics and metrics of the **Gemini** node, exit the editing page, click the node to open the Edit panel and click the **Overview** tab. ![openai_node_statistics](./assets/gemini_node_statistics.png)