## Pre-requisites

- Initially, only **one** of the sites added for replication may have data. After site-replication is successfully configured, this data is replicated to the other (initially empty) sites. Subsequently, objects may be written to any of the sites, and they will be replicated to all other sites.

- **Removing a site** is not allowed from a set of replicated sites once configured.

### Creating the `Settings` only once with `lru_cache` { #creating-the-settings-only-once-with-lru-cache }

Reading a file from disk is normally a costly (slow) operation, so you probably want to do it only once and then reuse the same settings object, instead of reading it for each request.

But every time we do:

```Python
Settings()

@REM We want to avoid trying to parse the external MAVEN_OPTS variable
SET INTERNAL_MAVEN_OPTS=

@REM Execute a user defined script before this one
if not "%MAVEN_SKIP_RC%"=="" goto skipRc
if exist "%PROGRAMDATA%\mavenrc.cmd" call "%PROGRAMDATA%\mavenrc.cmd" %*
@REM check for pre script, once with legacy .bat ending and once with .cmd ending

		"Total number of bytes failed at least once to replicate in the last hour on a bucket",
		bucketL, targetArnL)
	bucketReplLastHrFailedCountMD = NewGaugeMD(bucketReplLastHrFailedCount,
		"Total number of objects which failed replication in the last hour on a bucket",
		bucketL, targetArnL)
	bucketReplLastMinFailedBytesMD = NewGaugeMD(bucketReplLastMinFailedBytes,
		"Total number of bytes failed at least once to replicate in the last full minute on a bucket",

change unified the key-management aspect within MinIO.

The unified KMS-based approach has several advantages:

- Key management is now centralized. There is one way to change or rotate encryption keys.
   There used to be two different mechanisms - one for regular S3 objects and one for IAM data.
- Reduced server startup time. For IAM encryption with the root credentials, MinIO had

   *     href="https://github.com/google/guava#guava-google-core-libraries-for-java">flavor</a>)
   */
  @GwtIncompatible
  @J2ktIncompatible
  @CanIgnoreReturnValue
  @IgnoreJRERequirement // TODO: b/288085449 - Remove this once we use library-desugaring scents.
  @Beta // TODO: b/288085449 - Remove @Beta after we're sure that Java 8 APIs are safe for Android
  public FakeTicker advance(Duration duration) {
    return advance(duration.toNanos());
  }

        // Assert
        // Verify that sendrecv was called with MsrpcSamrCloseHandle
        verify(mockDcerpcHandle).sendrecv(any(MsrpcSamrCloseHandle.class));
        // Verify that close was called only once on the mockDcerpcHandle for MsrpcSamrCloseHandle
        verify(mockDcerpcHandle, times(1)).sendrecv(any(MsrpcSamrCloseHandle.class));
    }

    @Test

 * therefore every method of the listener will be called at most once. N.B. The {@link State#FAILED}
 * and {@link State#TERMINATED} states are terminal states, once a service enters either of these
 * states it cannot ever leave them.
 *
 * <p>Implementors of this interface are strongly encouraged to extend one of the abstract classes

   * segments, each governed by its own write lock. The segment lock is taken once for each explicit
   * write, and twice for each cache loading computation (once prior to loading the new value, and
   * once after loading completes). Much internal cache management is performed at the segment

    return a == b || (a != null && a.equals(b));
  }

  // This one-liner saves us from some ugly casts
  protected Entry<K, V> entry(K key, V value) {
    return mapEntry(key, value);
  }

  @Override
  protected void expectContents(Collection<Entry<K, V>> expected) {
    // TODO: move this to invariant checks once the appropriate hook exists?
    super.expectContents(expected);