Multiple fetch requests are slow.

[danielschwartz85]

Hi,

As a plugin (Applitools) we need to use the browser to download many resources, apx 70 per page.
The download speed seems very slow compared to a regular browser.

• My reproduction gave resulted of 5.5 seconds in Cypress vs 300ms in regular browser

Current behavior:

Fetch requests seem very slow for fetching many resources (compared to regular browser).

(the fetch "slowness" is exhibited in all frames)

Desired behavior:

A faster fetch method (maybe one that doesn't go through the proxy ?).

Steps to reproduce: (app code and test code)

See my reproduction:
https://github.com/danielschwartz85/cypress-proxy-speed
(This is a Cypress app with a test that shows the slow download speeds)

It uses this page:
https://danielschwartz85.github.io/cypress-fetch-page/

Versions

Cypress 3.1.4
Ubuntu 18.04.01
Electron 59, Chrome 71

Tnx!

[jennifer-shehane]

Thank you so much for the detailed issue! I was indeed able to reproduce this. We'll have the team look into what could be causing this issue.

Local run outside of Cypress

Visit in Cypress (even in new tab) - it's noticeably slower

[danielschwartz85]

Hi, Any updates on this issue ?
Tnx.

[jennifer-shehane]

No updates. We will comment when work is done on this issue.

[flotwig]

The issue seems to be related to the https-proxy. I ran the cypress-proxy-speed test suite against the cypress-slow-fetch website, hosted on HTTP at http://cypress-slow-fetch-http.chary.us/, and the loading time seems to be pretty normal once the assets are coming over HTTP:

I'm thinking that we're not properly re-using the TCP sockets made when we do intercepted HTTPS connections. I'll keep looking in to it.

Spec code:

describe('slow get', () => {
    it('http get it', () => {
        let url = 'http://cypress-slow-fetch-http.chary.us/'
        cy.visit(url);
    });
});

[flotwig]

#3531, when released, will add a couple of enhancements that speed up the proxy layer:

1. Switched to using a custom HTTP Agent implementation for all requests. Our implementation uses keep-alive for all HTTP/HTTPS requests, even if they go through a proxy. This enables us to achieve performance very close to the browser's performance.

2. Disabled Nagle's algorithm on the socket between Cypress and Chrome when going through the https-proxy. This greatly improves the performance of HTTPS requests since it means we don't unnecessarily buffer the proxied conversation.

Originally, this test case took 1705ms on my system. After these changes, your test case runs in 660ms on my system.

That's compared to 336ms in Chromium with HTTP/2 disabled, and 126ms in Chromium with HTTP/2 enabled.

There's still more we could do to improve performance:

1. Add HTTP/2 support - the main reason Cypress still isn't as fast as the browser, even after those changes, is because we don't take advantage of HTTP/2 where available. GitHub Pages supports HTTP/2 and that protocol is giving you those blazing fast load times you're seeing. Created an issue for it at Add HTTP/2 Support in Proxy Layer #3708

2. Cypress actually creates its own HTTPS server in https-proxy to serve HTTPS requests. If we didn't bother creating a TCP socket to make those requests to the internal HTTPS server, that would improve throughput. Issue: Don't create a new socket to do HTTPS interception through SNI server #3833

[bahmutov]

👏 Zach

…

On Thu, Mar 14, 2019 at 10:39 AM Zach Bloomquist ***@***.***> wrote: #3531 <#3531>, when released, will add a couple of enhancements that speed up the proxy layer: 1. Enabled forever-agent <https://github.com/request/forever-agent> in the request library, which improves pooling of all requests that go through the Cypress proxy. 2. Disabled Nagle's algorithm <https://en.wikipedia.org/wiki/Nagle%27s_algorithm> on the socket between Cypress and Chrome when going through the https-proxy. This greatly improves the performance of HTTPS requests since it means we don't unnecessarily buffer the proxied conversation. Originally, this test case took 1705ms on my system. After these changes, your test case runs in *660ms* on my system. That's compared to 336ms in Chromium with HTTP/2 disabled, and 126ms in Chromium with HTTP/2 enabled. There's still more we could do to improve performance: 1. Add HTTP/2 support - the main reason Cypress still isn't as fast as the browser, even after those changes, is because we don't take advantage of HTTP/2 where available. GitHub Pages supports HTTP/2 and that protocol is giving you those blazing fast load times you're seeing. Created an issue for it at #3708 <#3708> 2. Cypress actually creates its own HTTPS server in https-proxy to serve HTTPS requests. If we didn't bother creating a TCP socket to make those requests to the internal HTTPS server, that would improve throughput. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#3192 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ACHAplZjGXsMrcnHUXQnXBgt_6JZgqvTks5vWl8tgaJpZM4aOYW7> .

-- Dr. Gleb Bahmutov, PhD Schedule video chat / phone call / meeting with me via https://calendly.com/bahmutov gleb.bahmutov@gmail.com @bahmutov <https://twitter.com/@bahmutov> https://glebbahmutov.com/ https://glebbahmutov.com/blog https://github.com/bahmutov

[flotwig]

Gotta credit @brian-mann for this one, he eagle-eyed the setNoDelay option in the Node.js docs that we were previously unaware of

[bahmutov]

👍 Brian

…

Sent from my iPhone

On Mar 14, 2019, at 11:22, Zach Bloomquist ***@***.***> wrote: Gotta credit @brian-mann for this one, he eagle-eyed the setNoDelay option in the Node.js docs that we were previously unaware of — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub, or mute the thread.

[cypress-bot]

The code for this is done in cypress-io/cypress#3531, but has yet to be released.
We'll update this issue and reference the changelog when it's released.

[danielschwartz85]

Thanks for the work ! 👍

[cypress-bot]

Released in 3.3.0.