Google App Engine：按顺序在任务队列中调用多个后端

Question

我有一个6个后端servlet，我想按顺序调度它。

我想按BackendQueueServlet中指定的顺序安排它们的时间。

这是我的任务队列代码：

public class BackendQueueServlet extends HttpServlet {
    @SuppressWarnings("deprecation")
    protected void doPost(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        String key = "aaaaaa";

        // Add the task to the default queue.
        Queue queue = QueueFactory.getQueue("BackendQueue");


        queue.add(withUrl("/twitterservlet").method(Method.GET).param("key", key).header(
                "Host",
                BackendServiceFactory.getBackendService().getBackendAddress("twitterservlet")));


        queue.add(withUrl("/facebookservlet").method(Method.GET).param("key", key).header(
                "Host",
                BackendServiceFactory.getBackendService().getBackendAddress("facebookservlet")));

        queue.add(withUrl("/loadingservlet").method(Method.GET).param("key", key).header(
                "Host",
                BackendServiceFactory.getBackendService().getBackendAddress("loadingservlet")));

        queue.add(withUrl("/fbcomments").method(Method.GET).param("key", key).header(
                "Host",
                BackendServiceFactory.getBackendService().getBackendAddress("fbcomments")));

        queue.add(withUrl("/fbcomments").method(Method.GET).param("key", key).header(
                "Host",
                BackendServiceFactory.getBackendService().getBackendAddress("fbcomments")));

        queue.add(withUrl("/fbcomments").method(Method.GET).param("key", key).header(
                "Host",
                BackendServiceFactory.getBackendService().getBackendAddress("fbcomments")));        

    }
}

这是我的backend.xml

<backends>


      <backend name="twitterservlet">
        <class>B1</class>
        <options>
            <dynamic>true</dynamic>
        </options>
    </backend>

     <backend name="facebookservlet">
        <class>B1</class>
        <options>
            <dynamic>true</dynamic>
        </options>
    </backend>

    <backend name="loadingservlet">
        <class>B1</class>
        <options>
            <dynamic>true</dynamic>
        </options>
    </backend>


     <backend name="fbcomments">
        <class>B1</class>
        <options>
            <dynamic>true</dynamic>
        </options>
    </backend>


       <backend name="topinfluencer">
        <class>B1</class>
        <options>
            <dynamic>true</dynamic>
        </options>
    </backend>

</backends>