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stream: Fix readableState.awaitDrain mechanism
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In 6899094 (#2325),
the conditions for increasing `readableState.awaitDrain` when
writing to a piping destination returns false were changed so
that they could not actually be met, effectively leaving
`readableState.awaitDrain` with a constant value of 0.

This patch changes the conditions to testing whether the
stream for which `.write()` returned false is still a piping
destination, which was likely the intention of the original
patch.

Fixes: #5820
Fixes: #5257
PR-URL: #6023
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
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addaleax authored and Myles Borins committed Apr 20, 2016
1 parent b26fea1 commit 4392b4a
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Showing 2 changed files with 43 additions and 3 deletions.
6 changes: 3 additions & 3 deletions lib/_stream_readable.js
Original file line number Diff line number Diff line change
Expand Up @@ -538,9 +538,9 @@ Readable.prototype.pipe = function(dest, pipeOpts) {
// If the user unpiped during `dest.write()`, it is possible
// to get stuck in a permanently paused state if that write
// also returned false.
if (state.pipesCount === 1 &&
state.pipes[0] === dest &&
src.listenerCount('data') === 1 &&
// => Check whether `dest` is still a piping destination.
if (((state.pipesCount === 1 && state.pipes === dest) ||
(state.pipesCount > 1 && state.pipes.indexOf(dest) !== -1)) &&
!cleanedUp) {
debug('false write response, pause', src._readableState.awaitDrain);
src._readableState.awaitDrain++;
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40 changes: 40 additions & 0 deletions test/parallel/test-stream-pipe-await-drain.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,40 @@
'use strict';
const common = require('../common');
const stream = require('stream');

// This is very similar to test-stream-pipe-cleanup-pause.js.

const reader = new stream.Readable();
const writer1 = new stream.Writable();
const writer2 = new stream.Writable();

// 560000 is chosen here because it is larger than the (default) highWaterMark
// and will cause `.write()` to return false
// See: https://github.com/nodejs/node/issues/5820
const buffer = Buffer.allocUnsafe(560000);

reader._read = function(n) {};

writer1._write = common.mustCall(function(chunk, encoding, cb) {
this.emit('chunk-received');
cb();
}, 1);
writer1.once('chunk-received', function() {
setImmediate(function() {
// This one should *not* get through to writer1 because writer2 is not
// "done" processing.
reader.push(buffer);
});
});

// A "slow" consumer:
writer2._write = common.mustCall(function(chunk, encoding, cb) {
// Not calling cb here to "simulate" slow stream.

// This should be called exactly once, since the first .write() call
// will return false.
}, 1);

reader.pipe(writer1);
reader.pipe(writer2);
reader.push(buffer);

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