Application Events

Some applications may require initialization at the start and deinitialization in the end of app execution. First this implies that app may have pre-defined settings, for instance allocation of particular resources, data migration, cache pre-filling and so on. Second, at the stage of deinitialization, a reverse process take place, that is disposing allocated resources. Both stages are optional and depend on app logic and resources it manipulates.

Application Events Types

InfinniPlatfrom apps may handle the following events:

• After the application host has fully started and is about to wait for a graceful shutdown
• After the application host has fully stopped and is not wait for new requests

When the application host has fully started you have a chance to execute any kind of background tasks such as pre-filling data cache, data indexing and etc. When the application host has fully stopped you may dispose resources, save data retaining in memory and etc.

Note

You should pay attention that application may stop by exception or forcefully unloaded by administrative tools. Don’t rely that aforementioned event handlers will be invoked anyway. Instead of this the restoration logic should be implemented to help handle those emergencies.

Application Event Handler

To handle the application events there are two type of handlers represented by IAppStartedHandler and IAppStoppedHandler interfaces. The first is invoked when the application has started, the last is invoked when the application has stopped. All you need is to implement an appropriate handler and register it in IoC container.

Next example shows a handler which handles the application startup event.

public class MyAppStartedHandler : IAppStartedHandler
{
    public void Handle()
    {
        // App initialization code
    }
}

// ...

builder.RegisterType<MyAppStartedHandler>().As<IAppStartedHandler>().SingleInstance();

Asynchronous Event Handling

The application events is handled synchronously that is they don’t return result until completed. Such behavior is intentionally predefined so the application could control the launch-stop-launch transitions on its own. For instance, in the case when status of event handling is unnecessary you may enclose event handling in try/catch block, nevertheless it is highly recommended to recorded exception into the application log. If part of logics can be executed asynchronously it is recommended to run it in a new thread.

Note

It is the good practice when you minimize duration of the application start and stop. Accordingly this will improve the speed of app deployment and its re-launch.