How do I find out that the server with the rabbitmq consumer is down?

I have a producer server and a consumer server. The producer server sends the time to the rabbitmq queue. The consumer gets the time and puts it in the ScheduledExecutorService pool. At the specified time, the consumer completes the task. I am afraid that my consumer will fall and I will lose data. So I need to know in real time when my consumer server will crash. But I didn't find how to implement it. Please tell me how to do this?

You could use one of the many available services to monitor your server and report if it was unresponsive. As an example, you could use https://uptimerobot.com/ and expose a simple HTTP endpoint on your service then report when that becomes unavailable. There are MANY other comprehensive monitoring services available like: datadog, monitis, new relic etc. Alternatively, you could build your own by having another server which periodically checks that an HTTP endpoint or whatever is available on your consumer server and notifies you if it isn't.

Having said that, I would recommend changing your consumer to avoid data loss if it were to crash since you're creating scheduled tasks on your consumer, I suggest you have a look at Quartz scheduler and use that to schedule and process your jobs rather than using a custom-built solution. Quartz will ensure that your jobs get run even after a failure if you use a persistent store like the JDBCJobStore. http://www.quartz-scheduler.org/overview/