Setting offline=true via Network.emulateNetworkConditions does not stop serviceworkers from going online

When using the Network.emulateNetworkConditions to make the browser simulate offline mode, web applications that use serviceworkers are still able to bypass this setting and connect online. Therefore, this offline setting is not suitable to test the offline behaviour of these serviceworkers.

I am using the PyChromeDevTools:

    import PyChromeDevTools
    chrome = PyChromeDevTools.ChromeInterface()
    chrome.Network.emulateNetworkConditions(offline=True, latency=250, downloadThroughput=270, uploadThroughput=300)

I tried Puppeteer and WebDriverJS as well, using setNetworkConditions(), however the outcome is the same - serviceworkers bypass the offline setting and connects online.

The only thing that works is when you manually open Chrome DevTools, go to Network and tick the Offline box - this definitely stops all serviceworkers from connecting online.

[paulirish]

What version of Chrome has this Protocol Monitor?

It’s in Canary and probably beta, though probably not stable. Have to turn on DevTools experiments first. https://hackernoon.com/hidden-experimental-features-in-chrome-devtools-2ae93b11b628

See: https://umaar.com/dev-tips/166-protocol-monitor/

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Any hint on how I can get the sessionId of the subtarget, please?

there’s two options:

1. Target.setAutoAttach({autoAttach:true}) like the wiki page says. you’ll then get an event of related targets. and in there is a session ID. service workers are usually considered “related”, but it’s possible that this won’t fire, based on the SW process model.
2. after your Target.getTargets() response, you can then call Target.attachToTarget with the targetID you have. In the response you get a session ID. https://chromedevtools.github.io/devtools-protocol/tot/Target#method-attachToTarget

Good luck!

[ldiary]

Thanks a lot for all the help! I finally managed to simulate offline mode for serviceworkers. https://github.com/ldiary/marigoso/blob/master/notebooks/how-to-simulate-offline-browsing-for-serviceworker-testing-using-selenium-webdriver-and-chrome-devtools.ipynb