AWS EC2 实例：启动多个实例

Question

我想在新用户到达时创建 ec2 实例。我创建了一个 servlet 类来执行此操作。当用户到达时，我检查用户是否新的数据库，然后创建实例并发回他/她的 IP。当我为用户一个一个地向这个servlet发送http请求时，我得到了正确的IP。但是当我并行发送 HTTP 调用时（对于 user1 在 tab1 中发送请求，对于 user2 在 tab2 中同时发送请求，然后从 user1 HTTP 调用中获得响应）。当我这样做时，我得到了错误。有时user1说

"实例 ID 'i-0b79495934c3b5459' 不存在（服务： 亚马逊EC2；状态码：400；错误代码：InvalidInstanceID.NotFound； 请求 ID：e18a9eaa-cb1b-4130-a3ee-bf1b19fa184c)"

并且 user2 发送 IP 作为响应。请帮助我这是什么问题以及如何解决这个问题。 这是我创建的 Servlet 类。

public class GateKeeperController extends HttpServlet {
    private static final long serialVersionUID = 1L;
    BasicAWSCredentials awsCreds = new BasicAWSCredentials(credentials);
    AmazonEC2Client ec2Client = new AmazonEC2Client(awsCreds);
    RunInstancesRequest runInstancesRequest;
    RunInstancesResult runInstancesResult;
    Reservation reservation;
    Instance intstance;
    DescribeInstancesRequest describeInstanceRequest;
    DescribeInstancesResult describeInstanceResult;
    GatekeeperModal gateKeepermodal;
    String sourceAMI = null;
    String destinationAMI = null;

    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        HttpSession s = request.getSession();
        String userID = (String) request.getParameter("userID");
        Double lattitude = Double.parseDouble((String) request.getParameter("lat"));
        Double lonitude = Double.parseDouble((String) request.getParameter("long"));
        if (userID != null) {
            Pair coordinates = new Pair(lattitude, lonitude);
            RegionSelection targetRegion = new RegionSelection();
            String regionResult = targetRegion.getRegion(coordinates);
            String instanceIP = null;
            gateKeepermodal = new GatekeeperModal();
            try {
                if (gateKeepermodal.checkUserIsNew(userID)) {
                    instanceIP = startInstance(userID, regionResult);
                    if (instanceIP != null) {
                        response.getWriter().write(instanceIP);
                    }
                } 
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        } else {

        }
    }

    private String startInstance(String userID, String region) {
        String ami_id = new AMI().getAMI_ID(region);

        ec2Client.setEndpoint(region);
        runInstancesRequest = new RunInstancesRequest();
        runInstancesRequest.withImageId(ami_id).withInstanceType("t2.micro").withMinCount(1).withMaxCount(1)
                .withKeyName("GateKeeper_User").withSecurityGroups("GateKeeper User");
        runInstancesResult = ec2Client.runInstances(runInstancesRequest);
        reservation = runInstancesResult.getReservation();
        intstance = reservation.getInstances().get(0);
        String s1 = intstance.getState().getName();
        String s2 = InstanceStateName.Running.name();
        while (!s1.toLowerCase().equals(s2.toLowerCase())) {
            describeInstanceRequest = new DescribeInstancesRequest();
            describeInstanceRequest.withInstanceIds(intstance.getInstanceId());
            ec2Client.setEndpoint(region);
            describeInstanceResult = ec2Client.describeInstances(describeInstanceRequest);
            reservation = describeInstanceResult.getReservations().get(0);
            intstance = reservation.getInstances().get(0);
            s1 = intstance.getState().getName();
            s2 = InstanceStateName.Running.name();
        }
        GateKeeperUser user = new GateKeeperUser(userID, intstance.getInstanceId(), intstance.getPublicIpAddress(),
                region);
        Boolean result;
        try {
            result = gateKeepermodal.createUser(user);
            if (result) {
                return intstance.getPublicIpAddress();
            } else {
                return null;
            }

        } catch (SQLException e) {

        }
        return null;
    }
}

Answer 1

根据documentation：

"如果您成功运行 RunInstances 命令，然后 立即使用之前的实例 ID 运行另一个命令 在 RunInstances 的响应中提供，它可能会返回一个 InvalidInstanceID.NotFound 错误。这并不意味着实例确实 不存在。一些可能受到影响的特定命令是： DescribeInstances：要确认实例的实际状态，请运行 此命令使用指数退避算法。 TerminateInstances：要确认实例的状态，首先运行 使用指数退避算法的 DescribeInstances 命令。"