smartstream/test/test.backpressure.ts

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import { tap, expect } from '@push.rocks/tapbundle';
import { SmartDuplex, type ISmartDuplexOptions, StreamWrapper } from '../ts/index.js';
tap.test('should run backpressure test', async (toolsArg) => {
const done = toolsArg.defer();
async function testBackpressure() {
const stream1 = new SmartDuplex({
name: 'stream1',
objectMode: true,
writeFunction: async (chunk, tools) => {
await new Promise((resolve) => setTimeout(resolve, 10)); // Slow processing
console.log(`processed chunk ${chunk} in stream 1`);
return chunk; // Fast processing
},
});
const stream2 = new SmartDuplex({
name: 'stream2',
objectMode: true,
writeFunction: async (chunk, tools) => {
await new Promise((resolve) => setTimeout(resolve, 20)); // Slow processing
console.log(`processed chunk ${chunk} in stream 2`);
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await tools.push(chunk);
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// return chunk, optionally return ;
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},
}); // This stream processes data more slowly
const stream3 = new SmartDuplex({
objectMode: true,
name: 'stream3',
writeFunction: async (chunk, tools) => {
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await new Promise((resolve) => setTimeout(resolve, 200)); // Slow processing
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console.log(`processed chunk ${chunk} in stream 3`);
},
});
stream1.pipe(stream2).pipe(stream3);
let backpressured = false;
for (let i = 0; i < 200; i++) {
const canContinue = stream1.write(`Chunk ${i}`, 'utf8');
if (!canContinue) {
backpressured = true;
console.log(`Backpressure at chunk ${i}`);
}
}
stream1.end();
stream1.on('finish', () => {
console.log('Stream 1 finished processing.');
});
stream2.on('finish', () => {
console.log('Stream 2 finished processing.');
});
stream3.on('finish', () => {
console.log('Stream 3 finished processing.');
if (!backpressured) {
throw new Error('No backpressure was observed.');
} else {
done.resolve();
}
});
}
testBackpressure();
await done.promise;
});
await tap.start();