Mysterious async script timeout

[provegard]

I sometimes get async script timeouts in IE9 when tests are run at Sauce Labs. The Selenium log contains:

10:35:30.949 WARN - Exception thrown
org.openqa.selenium.TimeoutException: Timeout expired waiting for async script (WARNING: The server did not provide any stacktrace information)
Command duration or timeout: 1.27 seconds
Build info: version: '2.40.0', revision: 'fbe29a9', time: '2014-02-19 20:54:28'
System info: host: 'Sauce-Win7', ip: '172.20.42.201', os.name: 'Windows 7', os.arch: 'x86', os.version: '6.1', java.version: '1.7.0_65'
Session ID: 384e4496-90be-448e-9ae1-7829432a20ac
Driver info: org.openqa.selenium.ie.InternetExplorerDriver
Capabilities [{platform=WINDOWS, javascriptEnabled=true, elementScrollBehavior=0, ignoreZoomSetting=false, enablePersistentHover=true, ie.ensureCleanSession=false, browserName=internet explorer, enableElementCacheCleanup=true, unexpectedAlertBehaviour=dismiss, version=9, ie.usePerProcessProxy=false, cssSelectorsEnabled=true, ignoreProtectedModeSettings=false, requireWindowFocus=false, handlesAlerts=true, initialBrowserUrl=http://localhost:29849/, ie.forceCreateProcessApi=false, nativeEvents=true, proxy={proxyAutoconfigUrl=http://127.0.0.1:19876/proxy.pac, proxyType=pac}, browserAttachTimeout=0, ie.browserCommandLineSwitches=, takesScreenshot=true}]
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    at org.openqa.selenium.remote.ErrorHandler.createThrowable(ErrorHandler.java:193)
    at org.openqa.selenium.remote.ErrorHandler.throwIfResponseFailed(ErrorHandler.java:145)
    at org.openqa.selenium.remote.RemoteWebDriver.execute(RemoteWebDriver.java:573)
    at org.openqa.selenium.remote.RemoteWebDriver.executeAsyncScript(RemoteWebDriver.java:500)
    at sun.reflect.GeneratedMethodAccessor21.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.openqa.selenium.support.events.EventFiringWebDriver$2.invoke(EventFiringWebDriver.java:101)
    at com.sun.proxy.$Proxy2.executeAsyncScript(Unknown Source)
    at org.openqa.selenium.support.events.EventFiringWebDriver.executeAsyncScript(EventFiringWebDriver.java:225)
    at org.openqa.selenium.remote.server.handler.ExecuteAsyncScript.call(ExecuteAsyncScript.java:55)
    at org.openqa.selenium.remote.server.handler.ExecuteAsyncScript.call(ExecuteAsyncScript.java:1)
    at java.util.concurrent.FutureTask.run(Unknown Source)
    at org.openqa.selenium.remote.server.DefaultSession$1.run(DefaultSession.java:170)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)
10:35:30.958 WARN - Exception: Timeout expired waiting for async script (WARNING: The server did not provide any stacktrace information)
Command duration or timeout: 1.27 seconds

Note that the command duration/timeout was 1.27 seconds. My config sets allScriptsTimeout to 20000, and the log indicates the value is indeed set:

10:33:54.544 INFO - Executing: [set script timeoutt: 20000] at URL: /session/39e674e5-c1d3-4023-8b56-e737387e31ac/timeouts/async_script)
10:33:54.566 INFO - Done: /session/39e674e5-c1d3-4023-8b56-e737387e31ac/timeouts/async_script

What might cause this?

[juliemr]

Internet Explorer 9 is not one of our supported browsers (we support the two latest versions, see http://angular.github.io/protractor/#/browser-setup), so we can't guarantee that it will work perfectly. Sorry!