Stream Data

Use the TypeScript client to stream data from a Synnax cluster.

Streaming data is useful for real-time processing, visualization, and monitoring. This page guides you through using the TypeScript client to stream data from a Synnax cluster. If you’d like a conceptual overview of how streams work in Synnax, check out the streams page.

Open a Streamer

To start streaming data, call the openStreamer method on the client and provide a list of channels to stream:

const streamer = await client.openStreamer(["temperature1", "temperature2"]);

Reading Frames

Then, to read the next incoming data frame, call the read method on the streamer:

const frame = await streamer.read();

This call will block until a new frame is available. This frame may not contain data for every channel specified. For example, if we’re reading from two sensors that are being sampled by different devices at different rates, we may receive a frame containing data only for the first channel, followed by a frame containing data only for the second channel.

For more details on how to work with the returned frames, see the Series and Frames page.

Downsampling Frames

If you are interested in streaming data at a lower rate than is being written to the server, you can use the optional downsample parameter to specify the number of frames to skip before returning the next frame:

// setting the downsample factor to n means every nth sample will be retained
// e.g. for a downsample factor of 2, if [0.13, 0.12, 0.14, 0.13] is written,
// a streamer.read() will return [0.13, 0.14]

const streamer = await client.openStreamer(["temperature1", "temperature2"],2);

Handling Partial Frames

When reading frames from a streamer, it’s important to note that a frame may not contain data for every channel specified when opening the streamer. For example, if we’re reading from two sensors, temperature and pressure, that are being sampled by different devices at different rates, we may receive a frame containing data only for the first channel, followed by a frame containing only data for the second channel.

const frame = await streamer.read();
console.log(frame.at(-1))
// Output: { temperature: 25.0 }
const frame2 = await streamer.read();
console.log(frame2.at(-1))
// Output: { pressure: 1000.0 }
const frame3 = await streamer.read();
console.log(frame3.at(-1))
// Output: { temperature: 25.0, pressure: 1000.0 }

To check if a frame contains data for a specific channel, you can use the has method:

const frame = await streamer.read();
if (frame.has("temperature")) console.log(frame.get("temperature"));

Using an Async For Loop

The streamer implements an async iterator, which can be useful for continuously processing incoming frames of data:

for await (const frame of streamer) {
  // Process the frame
  const latestSamples = frame.at(-1);
}

Updating the Channel List

If you need to update the list of channels being streamed, you can call the update method on the streamer:

await streamer.update(["temperature1", "temperature2", "pressure"]);

Closing the Streamer

After you’re done streaming, it’s essential that you call the close method on the streamer to release the network connection and other related resources:

streamer.close();

We recommend using the streamer object within a try-finally block when possible. This ensures that the streamer is always closed, even if an exception is thrown:

const streamer = await client.openStreamer(["temperature1", "temperature2"]);
try {
  for await (const frame of streamer) {
    // Process the frame
  }
} finally {
  streamer.close();
}