4.12.0 Regression: CreateSnapshot causes images to be loaded many times #8679
Description
Current behavior
Currently if log is called (internally within a cypress command or by cy.log) all images which are in the process of loading will reload. On some pages this is generating so many network calls that xhr requests are getting stalled to the point that all tests time out.
I think this occurs when we clone the body element here https://github.com/cypress-io/cypress/blob/develop/packages/driver/src/cy/snapshots.js#L155
On some internal pages we have many XHR requests (which generate many logs) and many larger images. The reloading behavior is to the point that our tests time out due to requires xhr/fetch calls getting stuck behind all the images.
Desired behavior
Calling cy.log shouldn't trigger a reloading of all images
Test code to reproduce
Use this snippet with cy.open and disable cache off:
cy.visit('https://github.com/');
Array(15).fill().forEach(() => {
cy.log('Test log')
cy.wait(100);
})Using the above there were 1762 image requests when loading github homepage. Each image was loaded 33 times
Versions
- Cypress 5.2
- Using electron
- cypress open
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mtc3bmtc3b commentedon Sep 28, 2020
We are observing the same issue, also with Cypress 5.2 using cypress open, but using Chrome.
jennifer-shehane commentedon Sep 29, 2020
This was introduced in 4.12.0, likely by #8080, which you referenced at the line of code https://github.com/cypress-io/cypress/blob/develop/packages/driver/src/cy/snapshots.js#L155
The waiting of these resources could significantly slow down whatever is waiting on these resources to load.
Reproducible example
Disable cache in the Network tab of DevTools
index.htmlspec.js
4.11.0
4.12.0
crfrolik commentedon Sep 30, 2020
I don't know what "CreateSnapshot" is but I'm seeing the same images fly by the console repeatedly while a test runs, e.g.
(and many more images, repeated)
Could this be related?
EDIT I believe this is causing a timeout failure in a test that's using a mocked XHR
cy.route. The route oddly finishes immedately after the timeout occurs, consistently, which is suspicious.crfrolik commentedon Sep 30, 2020
(Chrome DevTools network view: ah, is this what is meant by "CreateSnapshot"?)
jennifer-shehane commentedon Oct 1, 2020
Snapshots are what we call the DOM that's captured on each command, so that when you scroll over the command log the DOM is rerendered to the state it was previously (aka time travel feature).
@crfrolik See if the issue of the requests is resolved after downgrading to 4.11.0, that should narrow down if this is the same issue.
crfrolik commentedon Oct 1, 2020
Thank you @jennifer-shehane - I downgraded to cypress 4.11.0 and the issue does not occur there, so that confirms my problem is a duplicate of this one.
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