4.44.0 breaks Javascript

[jogger2510]

My application loads multiple JS-enabled pages into tabs and then repeatedly loads content updated by JS by cycling through the tabs. Works fine with Selenium / Hu-Driver 4.43.0.

With the 4.44.0 versions content is no longer updated. Notably the log line
INFO::JS executor for org.htmlunit.WebClient@3e9f7694: Logging initialized @5498ms to org.htmlunit.jetty.util.log.StdErrLog
is now missing, which makes me assume the JS executor is no longer started.

[rbri]

Hmm, will have a look at this next week...

[jogger2510]

Update: Sorry for attributing this to 4.44.0. Turned out to be a race condition/timing issue making JS not executing just in different tabs.

Since I poll tabs in a round robin fashion, I found the number of tabs be the cause. Activating tabs with switchTo() for less than 100ms is a sure way to defeat JS.

Out of curiosity I checked DefaultJavaScriptExecutor.java. As I have extensive experience with Java job scheduling in different scenarios, I judge the code as problematic.

MAJOR OVERSIGHT: A sleep(10) is used. Years ago I timed that statement on various platforms. For a client side app on a typical workstation (which will have power saving enabled) this took 11ms on Linux, >100ms on MacOS, can´t remember Windoze (but high). If you must sleep instead of waiting for some condition, determine the due time for the next job and subtract at least 1 ms. There was an article somewhere, how MacOS puts entire application packages to sleep in order to avoid heating up CPU cores (Windoze acts similar). At least switchTo() and equivalent calls should interrupt the sleep, it would be better to use wait() with timeout, waiting on conditions that might trigger job execution.

WEAKNESS: There is a brute force search for the next executable job. For a large number of jobs a heap or circular buffer or even a sorted Java builtin would be much more efficient.