Handling OS signals

Default behavior

• SIGINT - return trace
• SIGTERM, SIGQUIT - shutdown service
• SIGUSR1 - reopen file descriptors for log (logrotate)

User behavior

The component os_signals::ProcessorComponent stores os_signals::Processor and listens to SIGUSR1 and SIGUSR2 signals. You can use AddListener function to subscribe to these signals.

For example, we use signal SIGUSR1 in components::Logging for reopening files after executing logrotate.

Example

1. Add in private field class

   os_signals::Subscriber signal_subscribe_

2. In in the component's constructor, register a signal listener. For example, components::Logging uses the following code:

           auto& signals_processor = context.FindComponent<os_signals::ProcessorComponent>().Get();
           context.RegisterScope(MakeScope([this, &signals_processor] {
               auto holder = signals_processor.AddListener(this, kName, os_signals::kSigUsr1, &Logging::OnLogRotate);
    
               // Force logrotate just after signal subscription to be sure we haven't lost signals during the loading.
               // If there were no signals, it's OK to re-open log files one more time.
               OnLogRotate();
    
               return holder;
           }));

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