Question about decoding messages in the browser

[Filip785]

Hi, thanks for the library.

I'm trying to use it to decode message in the browser, through WebSocket. I'm sending message from the websocket server in avro binary format as so:

// ...
const avscSchema = avsc.Type.forSchema({
    type: 'record',
    name: 'TestEvent',
    fields: [
        {
            name: 'event',
            type: 'string'
        },
        {
            name: 'count',
            type: 'int'
        }
    ]
});

app.publish('test_publish', avscSchema.toBuffer({event: 'TEST_EVENT', count: 1}));
// ...

Now, on the frontend I receive binary message like this:

// ...
const ws = new WebSocket('<connection_url>');

ws.addEventListener('message', async (e) => {
    // data is instanceof Blob
    const { data } = e;

    // convert to the JS object
    const arrayBuffer = await data.arrayBuffer();
    const buffer = Buffer.from(arrayBuffer);

    const avscSchema = avsc.Type.forSchema({
        type: 'record',
        name: 'TestEvent',
        fields: [
            {
                name: 'event',
                type: 'string'
            },
            {
                name: 'count',
                type: 'int'
            }
        ]
    });   

    // originalObject = {event: 'TEST_EVENT', count: 1}
    const originalObject = avscSchema.fromBuffer(buffer); 
});
// ...

Now, my question is, how can I know what type of schema is coming in from the message (as there can be multiple message types)? How can I know this beforehand so I can convert to correct object? Is it even possible?

Thanks.

[mtth]

Hi @Filip785. A common way of addressing this is with a schema registry, where each schema has a unique ID which you serialize alongside the data. If you have few events you could also combine them into a single union type which you would then use to serialize the messages (sending the combined schema when you first connect for example, so you don't need a separate registry).