These functions can be declared with `async def` or normal `def`.

### `startup` event { #startup-event }

To add a function that should be run before the application starts, declare it with the event `"startup"`:

{* ../../docs_src/events/tutorial001_py310.py hl[8] *}

<font color="#A6E22E">INFO</font>:     Application startup complete.
<font color="#A6E22E">INFO</font>:     Started server process [<font color="#A1EFE4">27370</font>]
<font color="#A6E22E">INFO</font>:     Waiting for application startup.
<font color="#A6E22E">INFO</font>:     Application startup complete.
<font color="#A6E22E">INFO</font>:     Started server process [<font color="#A1EFE4">27367</font>]

<font color="#A6E22E">INFO</font>:     Application startup complete.
<font color="#A6E22E">INFO</font>:     Started server process [<font color="#A1EFE4">27370</font>]
<font color="#A6E22E">INFO</font>:     Waiting for application startup.
<font color="#A6E22E">INFO</font>:     Application startup complete.
<font color="#A6E22E">INFO</font>:     Started server process [<font color="#A1EFE4">27367</font>]

<font color="#A6E22E">INFO</font>:     Application startup complete.
<font color="#A6E22E">INFO</font>:     Started server process [<font color="#A1EFE4">27370</font>]
<font color="#A6E22E">INFO</font>:     Waiting for application startup.
<font color="#A6E22E">INFO</font>:     Application startup complete.
<font color="#A6E22E">INFO</font>:     Started server process [<font color="#A1EFE4">27367</font>]

<font color="#A6E22E">INFO</font>:     Application startup complete.
<font color="#A6E22E">INFO</font>:     Started server process [<font color="#A1EFE4">27370</font>]
<font color="#A6E22E">INFO</font>:     Waiting for application startup.
<font color="#A6E22E">INFO</font>:     Application startup complete.
<font color="#A6E22E">INFO</font>:     Started server process [<font color="#A1EFE4">27367</font>]

  public void testStart_failed() {
    Exception exception = new Exception("deliberate");
    TestService service =
        new TestService() {
          @Override
          protected void startUp() throws Exception {
            super.startUp();
            throw exception;
          }
        };
    assertEquals(0, service.startUpCalled);
    RuntimeException e =

### Run Automatically on Startup { #run-automatically-on-startup }

In general, you will probably want the server program (e.g. Uvicorn) to be started automatically on server startup, and without needing any **human intervention**, to have a process always running with your API (e.g. Uvicorn running your FastAPI app).

  public void testStart_failed() {
    Exception exception = new Exception("deliberate");
    TestService service =
        new TestService() {
          @Override
          protected void startUp() throws Exception {
            super.startUp();
            throw exception;
          }
        };
    assertEquals(0, service.startUpCalled);
    RuntimeException e =

    CountDownLatch started = new CountDownLatch(1);
    FakeService service =
        new FakeService() {
          @Override
          protected void startUp() throws Exception {
            super.startUp();
            started.await();
          }
        };
    service.startAsync();
    service.stopAsync();
    started.countDown();
    service.awaitTerminated();

    CountDownLatch started = new CountDownLatch(1);
    FakeService service =
        new FakeService() {
          @Override
          protected void startUp() throws Exception {
            super.startUp();
            started.await();
          }
        };
    service.startAsync();
    service.stopAsync();
    started.countDown();
    service.awaitTerminated();