perspective-dev--perspective/examples/esbuild-remote/server/securities.mjs

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// ┃ Copyright (c) 2017, the Perspective Authors.                              ┃
// ┃ ╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌ ┃
// ┃ This file is part of the Perspective library, distributed under the terms ┃
// ┃ of the [Apache License 2.0](https://www.apache.org/licenses/LICENSE-2.0). ┃
// ┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛

import perspective from "@perspective-dev/client";

// Cache updates for faster update rates (but less data diversity)>
const CACHE_INPUT = false;

// If cached, how many updates to cache?
const CACHE_ENTRIES = 200;

// How many rows per update?
const UPDATE_SIZE = 50;

// Update every N milliseconds
const TICK_RATE = 20;

// Size limit of the server-side table
const TABLE_SIZE = 10000;

const SECURITIES = [
    "AAPL.N",
    "AMZN.N",
    "QQQ.N",
    "NVDA.N",
    "TSLA.N",
    "FB.N",
    "MSFT.N",
    "TLT.N",
    "XIV.N",
    "YY.N",
    "CSCO.N",
    "GOOGL.N",
    "PCLN.N",
];
const CLIENTS = [
    "Homer",
    "Marge",
    "Bart",
    "Lisa",
    "Maggie",
    "Moe",
    "Lenny",
    "Carl",
    "Krusty",
];

const __CACHE__ = [];

// perspective.initialize_profile_thread();

/*******************************************************************************
 *
 * Slow mode (new rows generated on the fly)
 */

function choose(choices) {
    return choices[Math.floor(Math.random() * choices.length)];
}

function newRows(total_rows) {
    const rows = [];
    for (let x = 0; x < total_rows; x++) {
        rows.push({
            name: choose(SECURITIES),
            client: choose(CLIENTS),
            lastUpdate: new Date(),
            chg: Math.random() * 20 - 10,
            bid: Math.random() * 10 + 90,
            ask: Math.random() * 10 + 100,
            vol: Math.random() * 10 + 100,
        });
    }
    return rows;
}

async function init_dynamic({ table_size, update_size, tick_rate }) {
    // Create a `table`.
    const table = await perspective.table(newRows(table_size), {
        limit: table_size,
        name: "securities",
    });

    // The `table` needs to be registered to a name with the Perspective
    // `WebSocketServer` in order for the client to get a proxy handle to it.

    // Loop and update the `table` oocasionally.
    (function postRow() {
        table.update(newRows(update_size));
        setTimeout(postRow, tick_rate);
    })();
    return table;
}

/*******************************************************************************
 *
 * Fast mode (rows pre-generated, cached as Arrows)
 */

async function newArrow(total_rows) {
    const table = await perspective.table(newRows(total_rows));
    const vw = await table.view();
    const arrow = await vw.to_arrow();
    vw.delete();
    table.delete();
    return arrow;
}

async function populate_cache(cache_entries) {
    for (let x = 0; x < cache_entries; x++) {
        let arrow = await newArrow(100);
        __CACHE__[x] = arrow;
    }
}

async function init_cached({ table_size, tick_rate, cache_entries }) {
    await populate_cache(cache_entries);
    const table = await perspective.table(newRows(table_size), {
        limit: table_size,
        name: "securities",
    });
    (function postRow() {
        const entry = __CACHE__[Math.floor(Math.random() * __CACHE__.length)];
        table.update(entry);
        setTimeout(postRow, tick_rate);
    })();
    return table;
}

export const getTable = (
    config = {
        cached: CACHE_INPUT,
        tick_rate: TICK_RATE,
        update_size: UPDATE_SIZE,
        table_size: TABLE_SIZE,
        cache_entries: CACHE_ENTRIES,
    },
) => {
    if (config.cached) {
        return init_cached(config);
    } else {
        return init_dynamic(config);
    }
};