# Convert JSON Messages into Avro > For the complete documentation index, see [llms.txt](https://docs.redpanda.com/llms.txt). Component-specific: [labs-full.txt](https://docs.redpanda.com/labs-full.txt) --- title: Convert JSON Messages into Avro latest-operator-version: v26.1.4 latest-console-tag: v3.7.3 latest-connect-version: 4.93.0 latest-redpanda-tag: v26.1.9 docname: issdemo-go page-component-name: labs page-version: master page-component-version: master page-component-title: Labs page-relative-src-path: issdemo-go.adoc page-edit-url: https://github.com/redpanda-data/redpanda-labs/edit/main/docs/modules/data-transforms/pages/issdemo-go.adoc description: Query live tracking data from the International Space Station and convert it from JSON to Avro using data transforms. page-git-created-date: "2025-05-06" page-git-modified-date: "2025-05-06" --- This example shows you how to query live tracking data from the International Space Station and convert it from JSON to Avro using Redpanda data transforms. This example uses cURL to query data from `api.open-notify.org` which is then piped through to Redpanda using the `rpk` command-line client. When the data is in Redpanda, itโ€™s converted from JSON to Avro using the transforms function. Then, you can see the converted data in Redpanda Console. ![Architectural Overview](https://docs.redpanda.com/labs/data-transforms/_images/iss_overview.png) ## [](#prerequisites)Prerequisites You must have the following: - At least version 1.20 of [Go](https://go.dev/doc/install) installed on your host machine. - [Install `rpk`](https://docs.redpanda.com/current/get-started/rpk-install/) on your host machine. - [Docker and Docker Compose](https://docs.docker.com/compose/install/) installed on your host machine. ## [](#run-the-lab)Run the lab 1. Clone this repository: ```bash git clone https://github.com/redpanda-data/redpanda-labs.git ``` 2. Change into the `data-transforms/iss_demo/` directory: ```bash cd redpanda-labs/data-transforms/go/iss_demo ``` 3. Set the `REDPANDA_VERSION` environment variable to at least version v23.3.1. Data transforms was introduced in this version. For all available versions, see the [GitHub releases](https://github.com/redpanda-data/redpanda/releases). For example: ```bash export REDPANDA_VERSION=v26.1.9 ``` 4. Set the `REDPANDA_CONSOLE_VERSION` environment variable to the version of Redpanda Console that you want to run. For all available versions, see the [GitHub releases](https://github.com/redpanda-data/redpanda/releases). > ๐Ÿ“ **NOTE** > > You must use at least version v3.0.0 of Redpanda Console to deploy this lab. For example: ```bash export REDPANDA_CONSOLE_VERSION=v3.7.3 ``` 5. Start Redpanda in Docker by running the following command: ```bash docker compose up -d --wait ``` 6. Post the Avro schema to the Schema Registry using a cURL command: ```bash ./post-schema.sh ``` Take a note of the schema ID that is returned from this command. In a clean environment this will be `1`. 7. Set up your rpk profile: ```bash rpk profile create iss_demo --from-profile profile.yml ``` Created and switched to new profile "iss\_demo". 8. Create the required topics `iss_json` and `iss_avro`: ```bash rpk topic create iss_json iss_avro ``` 9. Deploy the transforms function: ```bash rpk transform build rpk transform deploy --var=SCHEMA_ID=1 --input-topic=iss_json --output-topic=iss_avro ``` This example accepts the following environment variables: - `SCHEMA_ID` (**required**): The ID of the Avro schema stored in the Redpanda schema registry. Now, you can test that the data can be converted from JSON to Avro. 1. Get a single record representing the location of the ISS: ```bash curl http://api.open-notify.org/iss-now.json ``` Example output: ```json {"message": "success", "timestamp": 1695753164, "iss_position": {"latitude": "-12.8784", "longitude": "92.2935"}} ``` 2. Run `rpk topic produce`: ```bash rpk topic produce iss_json ``` 3. Paste the output of the cURL command into the prompt and press Ctrl+C to exit the prompt. 4. Consume the Avro topic using `rpk topic consume` and observe that the transforms function has converted it to Avro: ```bash rpk topic consume iss_avro --num 1 ``` Example output: ```json { "topic": "iss_avro", "value": "\u0000\u0000\u0000\u0000\u0001\ufffd\ufffd\u0011\ufffd\ufffd\ufffd)\ufffd\u0010X9\ufffd\ufffd\u0012W@\ufffd\ufffd\ufffd\ufffd\u000c", "timestamp": 1695753212929, "partition": 0, "offset": 0 } ``` 5. Open [Redpanda Console](http://localhost:8080/topics/iss_avro?p=-1&s=50&o=-1#messages) to view the decoded data. ![Redpanda Console showing the decoded message](https://docs.redpanda.com/labs/data-transforms/_images/iss_console.png) ## [](#files-in-the-example)Files in the example - [`iss.avsc`](https://github.com/redpanda-data/redpanda-labs/blob/main/data-transforms/iss_demo/iss.avsc): Avro schema used for conversion. - [`profile.yml`](https://github.com/redpanda-data/redpanda-labs/blob/main/data-transforms/iss_demo/profile.yml): Used to configure `rpk` with the `rpk profile` command. - [`transform.go`](https://github.com/redpanda-data/redpanda-labs/blob/main/data-transforms/iss_demo/transform.go): This is the Golang code that will be compiled to WebAssembly. This code: - Initializes the transform, including getting the schema from the Schema Registry and creating the `goavro` codec object (both stored in global variables). - Registers the callback `toAvro`. - `toAvro` parses the JSON into a struct `iss_now`, converts the struct into a map and then converts the map to Avro binary using the `goavro` codec. - Prepends the schema ID using the magic five bytes `0x0` followed by a BigEndian `uint32`. - This is all appended to the output slice. ## [](#clean-up)Clean up To shut down and delete the containers along with all your cluster data: ```bash docker compose down -v ``` ## [](#next-steps)Next steps You could set up a loop to poll the location of the ISS and produce it to the `iss_json` topic. For example: ```bash while true do line=`curl http://api.open-notify.org/iss-now.json -s` echo $line | rpk topic produce iss_json sleep 1 done ```