How to resolve Google App Engine Server Error

Initializing App Engine server
Oct 10, 2014 4:04:17 PM com.google.apphosting.utils.config.AppEngineWebXmlReader readAppEngineWebXml
INFO: Successfully processed C:\project\sriprasad_posttrade_projects\eclipse_workspace\KPGResearch\war\WEB-INF/appengine-web.xml
Oct 10, 2014 4:04:17 PM com.google.apphosting.utils.config.AppEngineWebXmlReader readAppEngineWebXml
SEVERE: Received exception processing C:\project\sriprasad_posttrade_projects\eclipse_workspace\KPGResearch\war\WEB-INF/appengine-web.xml
com.google.apphosting.utils.config.AppEngineConfigException: appengine-web.xml does not contain a <threadsafe> element.
See http://code.google.com/appengine/docs/java/config/appconfig.html#Using_Concurrent_Requests for more information.
You probably want to enable concurrent requests.
    at com.google.apphosting.utils.config.AppEngineWebXmlReader.readAppEngineWebXml(AppEngineWebXmlReader.java:87)
    at com.google.apphosting.utils.config.EarHelper.readWebModule(EarHelper.java:166)
    at com.google.appengine.tools.development.ApplicationConfigurationManager$WarServerConfigurationHandle.readConfiguration(ApplicationConfigurationManager.java:399)
    at com.google.appengine.tools.development.ApplicationConfigurationManager.<init>(ApplicationConfigurationManager.java:146)
    at com.google.appengine.tools.development.ApplicationConfigurationManager.newWarConfigurationManager(ApplicationConfigurationManager.java:88)
    at com.google.appengine.tools.development.DevAppServerImpl.<init>(DevAppServerImpl.java:138)
    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 com.google.appengine.tools.development.DevAppServerFactory.createDevAppServer(DevAppServerFactory.java:165)
    at com.google.appengine.tools.development.DevAppServerFactory.createDevAppServer(DevAppServerFactory.java:69)
    at com.google.appengine.tools.development.DevAppServerFactory.createDevAppServer(DevAppServerFactory.java:53)
    at com.google.appengine.tools.development.gwt.AppEngineLauncher.start(AppEngineLauncher.java:84)
    at com.google.gwt.dev.DevMode.doStartUpServer(DevMode.java:500)
    at com.google.gwt.dev.DevModeBase.startUp(DevModeBase.java:1055)
    at com.google.gwt.dev.DevModeBase.run(DevModeBase.java:804)
    at com.google.gwt.dev.DevMode.main(DevMode.java:309)

Resolution:

 add <threadsafe> tag to the app appengine-web.xml in war/WEB-INF directory

  syntax:    <threadsafe>true</threadsafe>