Question

如果启用了入站线程池，我发现Esper（v.7.1.0）中的数据丢失。这是演示这种奇怪行为的简单示例：

    Configuration config = new Configuration();
    // set up concurrent processing
    config.getEngineDefaults().getThreading().setThreadPoolInbound(true);

    EPServiceProvider epService = EPServiceProviderManager.getDefaultProvider(config);

    // simple schema
    epService.getEPAdministrator().createEPL("create objectarray schema LogLine as (account_name string, value int) ");
    // event for terminating context partition
    epService.getEPAdministrator().createEPL("create schema TerminateEvent() ");

    // Allocates context partition for each account_name. Start it on LogLine event and terminate on TerminateEvent.
    epService.getEPAdministrator()
            .createEPL("create context NestedCtx " + 
                       "context InitCtx start LogLine end TerminateEvent ," + 
                       "context AccountCtx partition by account_name from LogLine");
    // select to collect count of events per account_name.
    EPStatement statement = epService.getEPAdministrator().createEPL(" context NestedCtx select account_name, count(*) as total from LogLine output last when terminated ");
    // attach listener for printing results 
    statement.addListener(new UpdateListener() {

        @Override
        public void update(EventBean[] newEvents, EventBean[] oldEvents) {
            for (EventBean eventBean : newEvents) {
                String properties = Arrays.stream(eventBean.getEventType().getPropertyNames()).map((prop) -> {
                    return prop + " " + eventBean.get(prop);
                }).collect(Collectors.joining("; "));
                System.out.println(properties);
            }

        }
    });
    //send 3 LogLine events
    epService.getEPRuntime().sendEvent(new Object[] { "TEST", 10 }, "LogLine");
    epService.getEPRuntime().sendEvent(new Object[] { "TEST", 10 }, "LogLine");
    epService.getEPRuntime().sendEvent(new Object[] { "TEST", 10 }, "LogLine");

    // send terminate event in order to get results
    epService.getEPRuntime().sendEvent(Collections.emptyMap(), "TerminateEvent");
    System.out.println("finish");

问题是启用并发处理时不会调用UpdateListener。仅在禁用入站线程池时才打印结果。这种行为的原因是什么？

Answer 1

入站线程可以更改事件处理的顺序，因为JVM可以按任何顺序处理排队的任务。因此，当您的用例需要有序处理事件时，这意味着入站线程不是正确的选择。您的应用程序代码可以改为分配您的队列/线程并将事件关联到线程，以确保保留订单。例如as discussed in this StackOverflow question.

启用入站线程时Esper数据丢失

1 个答案: