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Don't store request specific data into the Layer object #113

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Don't store request specific data into the Layer object #113

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ff0facf
Don't store request specific data into the Layer object, should be im…
Feb 2, 2024
0cdf9a3
Move try ... catch back into its own function after inital review
Feb 2, 2024
735906a
Use "null" instead of "false" when there is no match in layer
Feb 6, 2024
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23 changes: 11 additions & 12 deletions index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -233,20 +233,19 @@ Router.prototype.handle = function handle(req, res, callback) {

// find next matching layer
var layer
var match
var match = null
var route

while (match !== true && idx < stack.length) {
while (!match && idx < stack.length) {
layer = stack[idx++]
match = matchLayer(layer, path)
route = layer.route

if (typeof match !== 'boolean') {
if (match && typeof match.path !== 'string') {
// hold on to layerError
layerError = layerError || match
}
route = layer.route

if (match !== true) {
if (!match) {
continue
}

Expand All @@ -257,7 +256,7 @@ Router.prototype.handle = function handle(req, res, callback) {

if (layerError) {
// routes do not match with a pending error
match = false
match = null
continue
}

Expand All @@ -271,13 +270,13 @@ Router.prototype.handle = function handle(req, res, callback) {

// don't even bother matching route
if (!has_method && method !== 'HEAD') {
match = false
match = null
continue
}
}

// no match
if (match !== true) {
if (!match) {
return done(layerError)
}

Expand All @@ -288,9 +287,9 @@ Router.prototype.handle = function handle(req, res, callback) {

// Capture one-time layer values
req.params = self.mergeParams
? mergeParams(layer.params, parentParams)
: layer.params
var layerPath = layer.path
? mergeParams(match.params, parentParams)
: match.params
var layerPath = match.path

// this should be done for the layer
self.process_params(layer, paramcalled, req, res, function (err) {
Expand Down
31 changes: 14 additions & 17 deletions lib/layer.js
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Original file line number Diff line number Diff line change
Expand Up @@ -38,8 +38,6 @@ function Layer(path, options, fn) {

this.handle = fn
this.name = fn.name || '<anonymous>'
this.params = undefined
this.path = undefined
this.regexp = pathRegexp(path, this.keys = [], opts)

// set fast path flags
Expand Down Expand Up @@ -111,35 +109,31 @@ Layer.prototype.match = function match(path) {
if (path != null) {
// fast path non-ending match for / (any path matches)
if (this.regexp.fast_slash) {
this.params = {}
this.path = ''
return true
return {
path: '',
params: {}
}
}

// fast path for * (everything matched in a param)
if (this.regexp.fast_star) {
this.params = {'0': decode_param(path)}
this.path = path
return true
return {
path: path,
params: {'0': decode_param(path)}
}
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This code has been around in this state for a very long time. My worry is that this new way creates garbage to collect (the new object added) on a hot path, which might be the reason it was done this way in the first place. Maybe @dougwilson will remember because this predates me by quite a bit. Without more context I would like to see us do some sort of performance pass on this since I don't think the feature addition would be worth it if we impacted performance in a negative way.

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A big part was preventing bail out due to the same variable being different shapes (i.e. here we now have something that can be a bool or an object, and v8 will struggle to make a bytecode and may be falling back to slow interpreter mode). Ideally if we want to keep things in hot paths fast they should definitely keep the same shapes for the byte code generator.

I don't remember off hand all the details for why it was mutating properties, but it was very likely to reduce generating a bunch of little objects only to trash them immediately. That can be addressed if an object pool is used for them, however.

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I haven't run through a perf yet as I am away, but I suspect using null instead of false would fix any bail outs since those would both be objects

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Yeah that is a good point as well. I think ideally we have some real world benchmarks to base these decisions off of, but I think in theory both the de-opt from different shapes and increased GC from these little objects will be perf regressions. It would be nice to comment these with links to the benchmarks at some point so that the context is kept in the code for future contributors.

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So far what I have done is run the perf with the test suite, which the deopts from there usually pretty low hanging fruit.

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But ya, if it needs a shaped object can make a no match object at the top level and return that reference for the no match

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I made the change to use null instead of false for the no match scenario (I added a new commit to help reading the new changes, but I can squash them if you prefer).

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I am not sure I see how that addresses the worry here. The change you made does mean you could return some of those boolean checks back to their original form I think, which is overall good to reduce the change for change's sake, but I think this comment thread here is about the method returning a boolean and not producing unnecessary garbage in the process.

I am not suggesting removing the last changes, but I think ideally we find a way to not create these objects yet still clean up the state after the layers are finished being handled.

}

// match the path
match = this.regexp.exec(path)
}

if (!match) {
this.params = undefined
this.path = undefined
return false
return null
}

// store values
this.params = {}
this.path = match[0]

// iterate matches
var keys = this.keys
var params = this.params
var params = {}

for (var i = 1; i < match.length; i++) {
var key = keys[i - 1]
Expand All @@ -151,7 +145,10 @@ Layer.prototype.match = function match(path) {
}
}

return true
return {
path: match[0],
params: params
}
}

/**
Expand Down
22 changes: 22 additions & 0 deletions test/req.params.js
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@ var Router = require('..')
var utils = require('./support/utils')

var createServer = utils.createServer
var assert = utils.assert
var request = utils.request

describe('req.params', function () {
Expand Down Expand Up @@ -67,6 +68,27 @@ describe('req.params', function () {
.expect(200, '{"foo":"bar"}', done)
})

it('should not keep parameters in memory', function (done) {
var router = Router()
var server = createServer(function (req, res, next) {
router(req, res, function (err) {
if (err) return next(err)
sawParams(req, res)
})
})

router.get('/:fizz', hitParams(1))

request(server)
.get('/buzz')
.end(function(err) {
if (err) return done(err)

assert.strictEqual(router.stack[0].params, undefined)
done()
})
})

describe('when "mergeParams: true"', function () {
it('should merge outside object with params', function (done) {
var router = Router({ mergeParams: true })
Expand Down