Question

我已经轻松编写了一个Java方法，等待更改状态，例如＆＃34; pending＆＃34;到＆＃34;跑步＆＃34;。它定期（延迟N秒）使用 DescribeInstanceRequest 轮询实例状态。

然而，要弄清楚它是否真的被终止是很棘手的，因为我永远不会被终止＆＃34;实例状态。这是我目前使用的，但我不确定这是否是一个好方法......

    /**
     * Checks up to 20 times, with linearly increasing delay, for instance state change from the argFromState to the 
     * argToState.
     * 
     * Typically you would call this method to wait until instance is "terminated", or when instance is "running".
     * 
     * @param argInstanceID
     * @param argFromState
     * @param argToState 
     * @see waitForInstance(String argInstanceID)
     */
    public void waitForStateChange(String argInstanceID, String argFromState, String argToState) {
        List<InstanceStatus> statuses = null;
        DescribeInstanceStatusRequest describeInstanceStatusRequest = 
                new DescribeInstanceStatusRequest().withInstanceIds(argInstanceID);
        DescribeInstanceStatusResult describeInstanceResult = null;

        LocalDateTime timeStart = LocalDateTime.now();

        InstanceStatus status = null;
        int code = 0;
        String name = argFromState;
        boolean inWantedState = false;

        int cnt = 1;
        while (!inWantedState && (cnt < 20)) { 
            describeInstanceResult = amazonEC2Client.describeInstanceStatus(describeInstanceStatusRequest);
            int numberOfStatuses = describeInstanceResult.getInstanceStatuses().size();
            if (numberOfStatuses > 0) {
                // We can do this because we requested details of PARTICULAR instance
                status = describeInstanceResult.getInstanceStatuses().get(0); 
                code = status.getInstanceState().getCode();
                name = status.getInstanceState().getName();
                inWantedState = name.equals(argToState);
            } else {

                // When instance is terminated, it does not show in the list. That is how we know it is terminated.
                if ("terminated".equals(argToState)) {
                    inWantedState = true;
                    LOGGER.info("Instance terminated.");
                } else {
                    LOGGER.info("Instance not in the list. It should be.");
                }
            }
            if (!inWantedState) { // status may have just changed...
                System.out.println(cnt + "(" + code + "/" + name + ") .. waiting " + (2 * cnt) + "sec for next try.");
                try {
                    Thread.sleep(2 * cnt * 1000);
                } catch (InterruptedException ex) {
                    Logger.getLogger(EC2Wrapper.class.getName()).log(Level.SEVERE, null, ex);
                }
            } // if
            ++cnt;
        } // while

        LocalDateTime timeEnd = LocalDateTime.now();
        Duration duration = Duration.between(timeStart, timeEnd);
        int secs = (int) duration.getSeconds();

        if (secs >= 60) {
            LOGGER.log(Level.INFO, "From `{0}` to `{1}` in {2} min.", 
                    new Object[]{argFromState, argToState, secs / 60});
        } else {
            LOGGER.log(Level.INFO, "From `{0}` to `{1}` in {2} sec.", 
                    new Object[]{argFromState, argToState, secs});
        }
    } // waitForStateChange() method

Answer 1

如果您正在谈论维护状态，那么就像我们在异步任务中所做的那样。设置取消（true）将触发具有新状态的回调。我们可以在doinBackground（）中访问相同的回调。

while(getStatus() == AsyncTask.Status.RUNNING){
// Do ur code ..
}

getStatus返回的

值是用新值更新的，礼貌取消（true）

在您的代码中可以实现同样的效果，如果在此处发布了一些代码段，将会很有帮助。

如何确保实例终止？

1 个答案: