Webdriver module hangs when starting a new sequence

[ferpasri]

Description

Sometimes, the TESTAR web driver hangs when starting the web URL and trying to fetch the initial web state. This provokes TESTAR to hang around 120 seconds, stop the system, and start a second try connection again.

Reproduce

The main issue is that this bug is not 'easy' to reproduce. But running a lot of sequences (e.g., 100) with a small number of actions (e.g., 1) sometimes shows this hang and restart bug behavior.

Possible cause

It seems that the origin cause of this bug is the implementation of a synchronized method that can potentially block some TESTAR threads to update the web tabs' handle information.

TESTAR_dev/webdriver/src/org/testar/monkey/alayer/webdriver/WdDriver.java

Lines 397 to 416 in 0682abe

	/*
	* Update the list of handles with added handles (new tabs)
	* Remove handles from closed tabs
	*/
	private synchronized static void updateHandlesList() {
	Set<String> currentHandles = remoteWebDriver.getWindowHandles();
	// Remove handles not present anymore (closed tabs)
	for (String handle : new ArrayList<>(windowHandles)) {
	if (!currentHandles.contains(handle)) {
	windowHandles.remove(handle);
	}
	}
	// Add new handles (new tabs), shouldn't be more than one
	for (String handle : currentHandles) {
	if (!windowHandles.contains(handle)) {
	windowHandles.add(handle);
	}
	}
	}

Possible solution

A solution we are investigating is changing this synchronized implementation with a multi-thread safe CopyOnWriteArrayList solution.