if (this.handle == null || !this.handle.isValid()) {
            // one extra acquire to keep this open till the stream is released
            this.handle =
                    this.file.openUnshared(this.openFlags, this.access, this.sharing, SmbConstants.ATTR_NORMAL, this.options).acquire();
            return this.handle;
        }
        return this.handle.acquire();
    }

    /**
     * Ensures that the file descriptor is openend

		return
	}

	go func() {
		r := rand.New(rand.NewSource(time.Now().UnixNano()))
		// Leader node (that successfully acquires the lock inside runCallhome)
		// will keep performing the callhome. If the leader goes down for some reason,
		// the lock will be released and another node will acquire it and take over
		// because of this loop.
		for {
			if !globalCallhomeConfig.Enabled() {
				return
			}

        @Test
        @DisplayName("open() acquires handle and closes it")
        void openDelegatesEnsureOpenAndCloses() throws Exception {
            SmbFileInputStream in = newStream();
            in.open();
            // ensureOpen returns acquired handle; try-with-resources must close it
            verify(mockHandle, times(1)).close();
            verify(mockHandle, atLeastOnce()).acquire();
        }

        @Test

* Nginx
* HAProxy

## Let's Encrypt { #lets-encrypt }

Before Let's Encrypt, these **HTTPS certificates** were sold by trusted third parties.

The process to acquire one of these certificates used to be cumbersome, require quite some paperwork and the certificates were quite expensive.

But then **[Let's Encrypt](https://letsencrypt.org/)** was created.

			locked = true
		}
	} else {
		if !lm.isWriteLock {
			lm.ref++
			locked = true
		}
	}

	return locked
}

const (
	lockRetryInterval = 50 * time.Millisecond
)

// lockLoop will acquire either a read or a write lock
//
// The call will block until the lock is granted using a built-in
// timing randomized back-off algorithm to try again until successful

    //                                                                    ================

    /**
     * Attempts to acquire a distributed lock for the specified operation.
     *
     * @param operationName the operation name used as the lock document ID.
     * @return {@code true} if the lock was acquired.
     */
    public boolean tryStartOperation(final String operationName) {
        return tryStartOperation(operationName, null);

 * only meant as a utility for developers that want to employ the model builder outside of the Maven build system, Maven
 * plugins should always acquire model builder instances via dependency injection. Developers might want to subclass
 * this factory to provide custom implementations for some of the components used by the model builder.
 *

### Locks

We have 3 different things that we synchronize on.

#### Http2Connection

This lock guards internal state of each connection. This lock is never held for blocking operations. That means that we acquire the lock, read or write a few fields and release the lock. No I/O and no application-layer callbacks.

#### Http2Stream

    void contextAccessor() {
        assertSame(ctx, transport.getContext());
    }

    @Test
    @DisplayName("acquire returns same instance")
    void acquireReturnsSameInstance() {
        SmbTransportImpl acquired = transport.acquire();
        assertSame(transport, acquired);
        transport.close(); // release once
    }

    @Test

///

### `startup` and `shutdown` together { #startup-and-shutdown-together }

There's a high chance that the logic for your *startup* and *shutdown* is connected, you might want to start something and then finish it, acquire a resource and then release it, etc.

Doing that in separated functions that don't share logic or variables together is more difficult as you would need to store values in global variables or similar tricks.