Page timeout => PROTOCOL_TIMEOUT on Network.emulateNetworkConditions

[paulirish]

Unexpected error... if you have a page that times out because it never finishes loading.. Lighthouse actually completes with this:

Runtime error encountered: Waiting for DevTools protocol response has exceeded the allotted time. (Method: Network.emulateNetworkConditions) LHErr or: PROTOCOL_TIMEOUT

verbose log sample

 status Gathering devtoolsLog & network records +0ms
  NetworkRecorder:verbose network semi-quiet +1ms
  statusEnd:verbose Gathering devtoolsLog & network records +0ms
  method => browser:verbose Network.emulateNetworkConditions {"latency":0,"downloadThroughput":0,"uploadThroughput":0,"offline":fals +0ms
  status Disconnecting from browser... +30s
  method => browser:verbose Storage.clearDataForOrigin {"origin":"http://localhost:10200","storageTypes":"appcache,file_systems,inde +2ms
  ChromeLauncher Killing Chrome instance 99316 +5ms
  <= event:verbose Inspector.detached {"reason":"Render process gone."} +36ms
  <= event:verbose Network.loadingFailed {"requestId":"5970A7A16C2CA4015516F5FDD6F076B2","timestamp":182731.290164,"type":"Document" +1ms
  NetworkRecorder:verbose network fully-quiet +0ms
  <= event:verbose Inspector.detached {"reason":"target_closed"} +0ms
  method <= browser OK:verbose Page.navigate {"frameId":"266F9C9AE5626FD51485D206C87C0D8F","loaderId":"5970A7A16C2CA4015516F5FDD6F07 +0ms
Runtime error encountered: Waiting for DevTools protocol response has exceeded the allotted time. (Method: Network.emulateNetworkConditions)
LHEr ror: PROTOCOL_TIMEOUT
    at Timeout._onTimeout (~/code/lighthouse/lighthouse-core/gather/driver.js:352:21)
    at listOnTimeout (internal/timers.js:531:17)
    at processTimers (internal/timers.js:475:7)

repro:

• yarn static-server
• node lighthouse-cli "http://localhost:10200/online-only.html?delay=75000"

The emulateNetworkConditions call comes from here:

lighthouse/lighthouse-core/gather/gather-runner.js

Lines 756 to 757 in a1571ba

	// Disable throttling so the afterPass analysis isn't throttled
	await driver.setThrottling(passContext.settings, {useThrottling: false});

and if that line is commented out.. we'd get The page provided is not HTML (served as MIME type ) as both a runtimeError and runWarning.

It's possible this root cause (a page that never loads) is what's behind some of these filed emulateNetworkConditions issues.

---

Possible LH fix: adding explicit detection of a page timeout.
Possible Chrome fix: Network.emulateNetworkConditions shouldn't timeout if the page is in a ~hung state.

[patrickhulce]

More broadly I want to try to almost completely eliminate PROTOCOL_TIMEOUT by adding a version of sendCommand that checks to see if Chrome is truly hung and just moves on if it's still responding. Yes, it technically represents something unexpected but the Lighthouse failure case is so painful and there's so little movement to ever actually fix any of these in Chromium (and I believe unrealistic to expect all of them to ever be fixed). Commands whose return type is void don't need to become fatal if Chrome never acks them...

[paulirish]

Possible LH fix: adding explicit detection of a page timeout.

we'll do this. timeout if the document itself is taking a longass time.
tricky part is figuring out what we skip in this case. if we're doing cleanup we dont want the cleanup protocol cmds to also hang

Possible Chrome fix: Network.emulateNetworkConditions shouldn't timeout if the page is in a ~hung state.

i'll file a bug for this.

More broadly I want to try to almost completely eliminate PROTOCOL_TIMEOUT

sounds good, too.