# Background Tasks

You can define background tasks to be run *after* returning a response.

This is useful for operations that need to happen after a request, but that the client doesn't really have to be waiting for the operation to complete before receiving the response.

This includes, for example:

* Email notifications sent after performing an action:

        if ( dgst != null && !isAsync() && ( getConfig().isRequireSecureNegotiate() || getErrorCode() == NtStatus.NT_STATUS_OK ) ) {
            // TODO: SMB2 - do we need to check the MIDs?
            // We only read what we were waiting for, so first guess would be no.
            boolean verify = dgst.verify(buffer, i, size, 0, this);
            this.verifyFailed = verify;
            return !verify;
        }
        return true;
    }

./mc ls -r --versions myminio/versioned/ >expanded_ns_versions.txt

./mc admin decom start myminio/ http://localhost:9000/tmp/xl/{1...10}/disk{0...1}

until $(./mc admin decom status myminio/ | grep -q Complete); do
	echo "waiting for decom to finish..."
	sleep 1
done

kill $pid_1
kill $pid_2

sleep 5

(minio server --address ":9001" http://localhost:9001/tmp/xl/{11...30}/disk{0...3} 2>&1 >/tmp/removed.log) &
pid=$!

            // so when oldFuture completes it is safe to allow the next submitted task to
            // proceed. Doing this immediately here lets the next task run without waiting for
            // the cancelled task's executor to run the noop AsyncCallable.
            //
            // ---
            //

<font color="#4E9A06">INFO</font>:     Started server process [<font color="#06989A">2265873</font>]
<font color="#4E9A06">INFO</font>:     Waiting for application startup.
<font color="#4E9A06">INFO</font>:     Application startup complete.
```

</div>

The command line program called `fastapi` is **FastAPI CLI**.

    latch = new CountDownLatch(1);
    future = createListenableFuture(Boolean.TRUE, null, latch);
  }

  @Override
  protected void tearDown() throws Exception {

    // Make sure we have no waiting threads.
    latch.countDown();
  }

  /** Constructs a listenable future with a value available after the latch has counted down. */
  protected abstract <V> ListenableFuture<V> createListenableFuture(

    TimeoutException e =
        assertThrows(
            TimeoutException.class, () -> service.startAsync().awaitRunning(1, MILLISECONDS));
    assertThat(e)
        .hasMessageThat()
        .isEqualTo("Timed out waiting for Foo [STARTING] to reach the RUNNING state.");
  }

  private static class TestService extends AbstractIdleService {
    int startUpCalled = 0;
    int shutDownCalled = 0;

      if (compareAndSet(currentRunner, blocker)) {
        // Thread.interrupt can throw arbitrary exceptions due to the nio InterruptibleChannel API
        // This will make sure that tasks don't get stuck busy waiting.
        // Some of this is fixed in jdk11 (see https://bugs.openjdk.java.net/browse/JDK-8198692) but
        // not all.  See the test cases for examples on how this can happen.
        try {

 <font color="#4E9A06">╰─────────────────────────────────────────────────────╯</font>

<font color="#4E9A06">INFO</font>:     Started server process [<font color="#06989A">2306215</font>]
<font color="#4E9A06">INFO</font>:     Waiting for application startup.
<font color="#4E9A06">INFO</font>:     Application startup complete.
<font color="#4E9A06">INFO</font>:     Uvicorn running on <b>http://0.0.0.0:8000</b> (Press CTRL+C to quit)
```

</div>

      assertBitEquals(prev, at.get());
      assertTrue(at.compareAndSet(prev, x));
      assertBitEquals(x, at.get());
      prev = x;
    }
  }

  /** compareAndSet in one thread enables another waiting for value to succeed */
  public void testCompareAndSetInMultipleThreads() throws Exception {
    final AtomicDouble at = new AtomicDouble(1.0);
    Thread t =
        newStartedThread(