Read Data

Use the TypeScript Client to read from a Synnax cluster.

The TypeScript client supports several different methods for reading data from a cluster. We can read directly from a channel, read from multiple channels at once, or use iterators to efficiently process large amounts of data.

Reading from a Channel

The simplest way to read data from Synnax is to use the read method on a Channel object:

const channel = await client.channels.retrieve("temperature");
const start = new Date('2023-02-12T12:30:00Z');
const end = new Date('2022-02-12T14:30:00Z');

const series = await channel.read(start, end);

The returned data is a MultiSeries, which maintains a very similar interface to a JavaScript typed array (e.g. Float32Array, Int32Array, etc.). We can convert the returned data to a JavaScript array easily:

const data = Array.from(series);

For more information on MultiSeries and their underlying Series object, see Series.

Reading from Multiple Channels

We can also read from multiple channels at once by calling the read method on the client. This method takes a list of channel names/keys and a time range:

import { TimeStamp } from "@synnaxlabs/pluto";

const start = TimeStamp.now();
const end = start.add(TimeStamp.seconds(10));
const frame = await client.read({ start, end }, ["temperature", "humidity"]);

The returned data is a Frame object, which contains a MultiSeries for each channel. To access the data for a specific channel, we can use the get method:

const temperature = frame.get("temperature");
const humidity = frame.get("humidity");

For more information on the Frame class, see Frames.

Using Iterators

While the above methods will cover most use cases, there are situations where it’s necessary to query large volumes of data. Iterators provide a way to efficiently process data in chunks:

const start = TimeStamp.now();
const end = start.add(TimeStamp.seconds(10));

const iterator = await client.openIterator(
    { start, end }, 
    ["temperature", "humidity"]
);
try {
    for await (const frame of iterator) {
        const temperature = frame.get("temperature");
        const humidity = frame.get("humidity");
        // Process the data
    }
} finally {
    iterator.close();
}

It’s very important to close the iterator when you’re done with it to free up network resources. We highly recommend wrapping the iterator in a try...finally block to ensure that it’s closed properly in the event of an error.