For a few weeks now I’ve been plagued with timeouts while updating my App Engine apps. At first I thought it was a problem in the Intellij EAP beta I was running, but today I spent some time digging into it.

It seems to be unrelated to the EAP, as I get the same behavior with the App Engine command-line tools- timeout failure parsing web.xml roughly 75% of the time. It looks like this:

Nov 17, 2010 4:32:54 PM com.google.apphosting.utils.config.AbstractConfigXmlReader readConfigXml SEVERE: Received exception processing /Users/armhold/work/git-mega-repo/mystore/out/artifacts/Typing_Web_exploded/WEB-INF/web.xml com.google.apphosting.utils.config.AppEngineConfigException: Received IOException parsing the input stream for /Users/armhold/work/git-mega-repo/mystore/out/artifacts/Typing_Web_exploded/WEB-INF/web.xml at com.google.apphosting.utils.config.AbstractConfigXmlReader.getTopLevelNode(AbstractConfigXmlReader.java:210) at com.google.apphosting.utils.config.AbstractConfigXmlReader.parse(AbstractConfigXmlReader.java:228) at com.google.apphosting.utils.config.WebXmlReader.processXml(WebXmlReader.java:142) at com.google.apphosting.utils.config.WebXmlReader.processXml(WebXmlReader.java:22) at com.google.apphosting.utils.config.AbstractConfigXmlReader.readConfigXml(AbstractConfigXmlReader.java:111) at com.google.apphosting.utils.config.WebXmlReader.readWebXml(WebXmlReader.java:73) at com.google.appengine.tools.admin.Application.(Application.java:105) at com.google.appengine.tools.admin.Application.readApplication(Application.java:151) at com.google.appengine.tools.admin.AppCfg.(AppCfg.java:115) at com.google.appengine.tools.admin.AppCfg.(AppCfg.java:61) at com.google.appengine.tools.admin.AppCfg.main(AppCfg.java:57) Caused by: java.net.ConnectException: Operation timed out After some digging around, it seems to be related to a timeout deep in the bowels of Java’s XML libs while trying to validate the DTD for web.xml.

The fix is simple: elide the DTD declaration from the top of your web.xml:

<!DOCTYPE web-app    PUBLIC “-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN”    ”http://java.sun.com/dtd/web-app_2_3.dtd”>