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Nestjs Request and Application Lifecycle

I am looking for information about the request and application life-cycle for The NestJS framework. Specifically:

  1. What is the order of execution of the following processes in a request, for a route that implements: middleware, pipes, guards, interceptors, and any other potential request process

  2. What is the lifespan of modules and providers in a NestJS application? Do they last for the lifespan of a request, or the application, or something else?

  3. Are there any lifecycle hooks, in addition to OnModuleInit and OnModuleDestroy?

  4. What causes a Module to be destroyed (and trigger the OnModuleDestroy event)?

Solution

  • What is the order of execution of the following processes in a request, for a route that implements: middleware, pipes, guards, interceptors, and any other potential request process

    The common order is:

    • Middlewares
    • Guards
    • Interceptors (before the stream is manipulated)
    • Pipes
    • Interceptors (after the stream is manipulated)
    • Exception filters (if any exception is caught)

    What is the lifespan of modules and providers in a NestJS application? Do they last for the lifespan of a request, or the application, or something else?

    They do last for the lifespan of the application. Modules are destroyed when a NestApplication or a NestMicroservice is being closed (see close method from INestApplication).

    Are there any lifecycle hooks, in addition to OnModuleInit and OnModuleDestroy?

    No there aren't at the moment.

    What causes a Modeule to be destroyed (and trigger the OnModuleDestroy event)?

    See my answer to the second point. As you look interested in lifecyle hooks, you might pay some interest to issues #938 and #550