Skip to content
Permalink
Browse files

stream: use lazy registration for drain for fast destinations

PR-URL: #29095
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
  • Loading branch information...
ronag authored and targos committed Aug 12, 2019
1 parent 178caa5 commit e2a2a3f4ddde034b758f9834ad74daff13e63518
@@ -681,20 +681,17 @@ Readable.prototype.pipe = function(dest, pipeOpts) {
dest.end();
}

// When the dest drains, it reduces the awaitDrain counter
// on the source. This would be more elegant with a .once()
// handler in flow(), but adding and removing repeatedly is
// too slow.
const ondrain = pipeOnDrain(src);
dest.on('drain', ondrain);
let ondrain;

var cleanedUp = false;
function cleanup() {
debug('cleanup');
// Cleanup event handlers once the pipe is broken
dest.removeListener('close', onclose);
dest.removeListener('finish', onfinish);
dest.removeListener('drain', ondrain);
if (ondrain) {
dest.removeListener('drain', ondrain);
}
dest.removeListener('error', onerror);
dest.removeListener('unpipe', onunpipe);
src.removeListener('end', onend);
@@ -708,7 +705,7 @@ Readable.prototype.pipe = function(dest, pipeOpts) {
// flowing again.
// So, if this is awaiting a drain, then we just call it now.
// If we don't know, then assume that we are waiting for one.
if (state.awaitDrain &&
if (ondrain && state.awaitDrain &&
(!dest._writableState || dest._writableState.needDrain))
ondrain();
}
@@ -729,6 +726,14 @@ Readable.prototype.pipe = function(dest, pipeOpts) {
debug('false write response, pause', state.awaitDrain);
state.awaitDrain++;
}
if (!ondrain) {
// When the dest drains, it reduces the awaitDrain counter
// on the source. This would be more elegant with a .once()
// handler in flow(), but adding and removing repeatedly is
// too slow.
ondrain = pipeOnDrain(src);
dest.on('drain', ondrain);
}
src.pause();
}
}
@@ -1,5 +1,6 @@
'use strict';
const common = require('../common');
const assert = require('assert');
const { Readable, Writable, PassThrough } = require('stream');

{
@@ -65,3 +66,25 @@ const { Readable, Writable, PassThrough } = require('stream');
wrapper.resume();
wrapper.on('end', common.mustCall());
}

{
// Only register drain if there is backpressure.
const rs = new Readable({ read() {} });

const pt = rs
.pipe(new PassThrough({ objectMode: true, highWaterMark: 2 }));
assert.strictEqual(pt.listenerCount('drain'), 0);
pt.on('finish', () => {
assert.strictEqual(pt.listenerCount('drain'), 0);
});

rs.push('asd');
assert.strictEqual(pt.listenerCount('drain'), 0);

process.nextTick(() => {
rs.push('asd');
assert.strictEqual(pt.listenerCount('drain'), 0);
rs.push(null);
assert.strictEqual(pt.listenerCount('drain'), 0);
});
}
@@ -52,11 +52,4 @@ function drain() {

w.end = common.mustCall();

// Just for kicks, let's mess with the drain count.
// This verifies that even if it gets negative in the
// pipe() cleanup function, we'll still function properly.
r.on('readable', function() {
w.emit('drain');
});

r.pipe(w);

0 comments on commit e2a2a3f

Please sign in to comment.
You can’t perform that action at this time.