73 lines
2.5 KiB
JavaScript
73 lines
2.5 KiB
JavaScript
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/* A few users have reported having issues understanding backpressure and how to deal with it.
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*
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* Backpressure is the buildup of unacknowledged data; you can't just call ws.send without checking for backpressure.
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* Data doesn't just, poof, immediately jump from your server to the receiver - the receiver has to actually... receive it.
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* That happens with ACKs, controlling the transmission window.
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*
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* This applies to _EVERYTHING_ computer science (not just uWS); files, sockets, queues, and so on. If you're building
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* web services without taking backpressure into account you're not developing proper solutions - you're fucking around.
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*
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* Any slow receiver can wreck your whole server if you're not taking backpressure into account.
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*
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* The following is a (preposterous) example of how data can be pushed according to backpressure.
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* Do not take this as a way to actually write code, this is horrible, but it shows the concept clearly.
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*
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*/
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/* Number between thumb and index finger */
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const backpressure = 1024;
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/* Used for statistics */
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let messages = 0;
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let messageNumber = 0;
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const uWS = require('../dist/uws.js');
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const port = 9001;
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const app = uWS./*SSL*/App({
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key_file_name: 'misc/key.pem',
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cert_file_name: 'misc/cert.pem',
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passphrase: '1234'
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}).ws('/*', {
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/* Options */
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compression: 0,
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maxPayloadLength: 16 * 1024 * 1024,
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/* We need a slightly higher timeout for this crazy example */
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idleTimeout: 60,
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/* Handlers */
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open: (ws, req) => {
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console.log('A WebSocket connected via URL: ' + req.getUrl() + '! Pushing data now!');
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/* We begin our example by sending until we have backpressure */
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while (ws.getBufferedAmount() < backpressure) {
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ws.send("This is a message, let's call it " + messageNumber);
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messageNumber++;
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messages++;
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}
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},
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drain: (ws) => {
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/* Continue sending when we have drained (some) */
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while (ws.getBufferedAmount() < backpressure) {
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ws.send("This is a message, let's call it " + messageNumber);
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messageNumber++;
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messages++;
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}
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},
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close: (ws, code, message) => {
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console.log('WebSocket closed');
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}
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}).any('/*', (res, req) => {
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res.end('Nothing to see here!');
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}).listen(port, (token) => {
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if (token) {
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console.log('Listening to port ' + port);
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} else {
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console.log('Failed to listen to port ' + port);
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}
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});
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/* Start a timer to check how fast we end up sending.
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* Not a benchmark, just statistics. */
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setInterval(() => {
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console.log("Sent " + messages + " messages last second");
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messages = 0;
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}, 1000);
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