Appengine后端关机挂钩是否是随机的？

Question

I am having problem with shutdown code. So I made a minimal backend servlet to test this.

Anyone out there that knows if shutdown hooks are reliable or not!?

My logs do not show any _ah/stop line at all ... at the moment.

I suspect that it could be related to that the logs disappears but would like to get that confirmed. Ie that ApiProxi.flushLogs() does not work in shutdown mode.

One funny note is that when I got mad and duplicated the line (15 times) ...

            log.info("LIFECYCLE - Shutdown hook invoked");

... I saw _ah/stop lines.

@Override
public void destroy() {
    super.destroy();
    log.info("LIFECYCLE - Shutting down");
    ApiProxy.flushLogs();
}

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    log.info("doGet()");
    ApiProxy.flushLogs();
}

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    log.info("doPost()");
    ApiProxy.flushLogs();
}




@Override
public void init(ServletConfig config) throws ServletException {
    super.init(config);
    log.info("LIFECYCLE - Starting up");
    ApiProxy.flushLogs();
    LifecycleManager.getInstance().setShutdownHook(new ShutdownHook() {
        public void shutdown() {
            log.info("LIFECYCLE - Shutdown hook invoked");
            ApiProxy.flushLogs();
        }
    });
}
@Override
public void destroy() {
    super.destroy();
    log.info("LIFECYCLE - Shutting down");
    ApiProxy.flushLogs();
}

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    log.info("doGet()");
    ApiProxy.flushLogs();
}

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    log.info("doPost()");
    ApiProxy.flushLogs();
}

Answer 1

Did you read the manual?

https://developers.google.com/appengine/docs/java/backends/?hl=en#Shutdown

You can manually shutdown your backend to trigger the shutdown handler. But yes, they can happen randomly.

Answer 2

It does seem that the shutdown handler is not guaranteed to be called. This happens to my app almost all the time. I am using python2.7 and register a shutdown handler to log some information. Does not get called 95% of the time. Backend log says proces terminated as backend took too long to shut down.