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[v9.x] stream: always reset awaitDrain when emitting data #18911

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13 changes: 4 additions & 9 deletions lib/_stream_readable.js
Original file line number Diff line number Diff line change
Expand Up @@ -266,6 +266,7 @@ function readableAddChunk(stream, chunk, encoding, addToFront, skipChunkCheck) {

function addChunk(stream, state, chunk, addToFront) {
if (state.flowing && state.length === 0 && !state.sync) {
state.awaitDrain = 0;
stream.emit('data', chunk);
stream.read(0);
} else {
Expand Down Expand Up @@ -465,6 +466,7 @@ Readable.prototype.read = function(n) {
n = 0;
} else {
state.length -= n;
state.awaitDrain = 0;
}

if (state.length === 0) {
Expand Down Expand Up @@ -634,17 +636,12 @@ Readable.prototype.pipe = function(dest, pipeOpts) {
ondrain();
}

// If the user pushes more data while we're writing to dest then we'll end up
// in ondata again. However, we only want to increase awaitDrain once because
// dest will only emit one 'drain' event for the multiple writes.
// => Introduce a guard on increasing awaitDrain.
var increasedAwaitDrain = false;
src.on('data', ondata);
function ondata(chunk) {
debug('ondata');
increasedAwaitDrain = false;
var ret = dest.write(chunk);
if (false === ret && !increasedAwaitDrain) {
debug('dest.write', ret);
if (ret === false) {
// If the user unpiped during `dest.write()`, it is possible
// to get stuck in a permanently paused state if that write
// also returned false.
Expand All @@ -654,7 +651,6 @@ Readable.prototype.pipe = function(dest, pipeOpts) {
!cleanedUp) {
debug('false write response, pause', state.awaitDrain);
state.awaitDrain++;
increasedAwaitDrain = true;
}
src.pause();
}
Expand Down Expand Up @@ -830,7 +826,6 @@ function resume_(stream, state) {
}

state.resumeScheduled = false;
state.awaitDrain = 0;
stream.emit('resume');
flow(stream);
if (state.flowing && !state.reading)
Expand Down
35 changes: 35 additions & 0 deletions test/parallel/test-stream-pipe-manual-resume.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,35 @@
'use strict';
const common = require('../common');
const stream = require('stream');

function test(throwCodeInbetween) {
// Check that a pipe does not stall if .read() is called unexpectedly
// (i.e. the stream is not resumed by the pipe).

const n = 1000;
let counter = n;
const rs = stream.Readable({
objectMode: true,
read: common.mustCallAtLeast(() => {
if (--counter >= 0)
rs.push({ counter });
else
rs.push(null);
}, n)
});

const ws = stream.Writable({
objectMode: true,
write: common.mustCall((data, enc, cb) => {
setImmediate(cb);
}, n)
});

setImmediate(() => throwCodeInbetween(rs, ws));

rs.pipe(ws);
}

test((rs) => rs.read());
test((rs) => rs.resume());
test(() => 0);