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feat(chain): schedule handlers to the next tick #1798

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merged 1 commit into from Jul 31, 2019
Merged

feat(chain): schedule handlers to the next tick #1798

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4 changes: 3 additions & 1 deletion lib/chain.js
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Expand Up @@ -161,7 +161,9 @@ function call(handler, err, req, res, _next) {
return;
} else if (!hasError && arity < 4) {
// request-handling middleware
handler(req, res, next);
process.nextTick(function nextTick() {
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Have you run the benchmarks with this PR? Consider this implementation instead:
process.nextTick(handler, req, res, next);
Looking at the implementation of nextTick with Julien, it isn't clear which would be faster.

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yes I run, looks like no effect

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The goal would be cleaner flamegraphs not faster execution.

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Is this enough to reset the FG stack? Or do we need setImmediate?

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cc @misterdjules

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What do we mean by "FG stack"? If the question is whether the handler call's stack frame would not have the previous handler as a parent stack frame, the answer is yes, it would not have the previous handler as a parent stack frame.

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Ah Peter clarified that FG is for Flame Graphs :)

handler(req, res, next);
});
return;
}

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20 changes: 12 additions & 8 deletions test/chain.test.js
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@@ -1,6 +1,7 @@
'use strict';
/* eslint-disable func-names */

var domain = require('domain');
var Chain = require('../lib/chain');

if (require.cache[__dirname + '/lib/helper.js']) {
Expand Down Expand Up @@ -184,7 +185,7 @@ test('onceNext prevents double next calls', function(t) {
});

test('throws error for double next calls in strictNext mode', function(t) {
var doneCalled = 0;
t.expect(1);
var chain = new Chain({
strictNext: true
});
Expand All @@ -194,7 +195,15 @@ test('throws error for double next calls in strictNext mode', function(t) {
next();
});

try {
var testDomain = domain.create();

testDomain.on('error', function onError(err) {
t.equal(err.message, "next shouldn't be called more than once");
testDomain.exit();
t.done();
});

testDomain.run(function run() {
chain.run(
{
startHandlerTimer: function() {},
Expand All @@ -206,14 +215,9 @@ test('throws error for double next calls in strictNext mode', function(t) {
{},
function(err) {
t.ifError(err);
doneCalled++;
t.equal(doneCalled, 1);
t.done();
}
);
} catch (err) {
t.equal(err.message, "next shouldn't be called more than once");
}
});
});

test('calls req.startHandlerTimer', function(t) {
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