org.eclipse.jgit.storage.dht/src/org/eclipse/jgit/storage/dht/spi/Database.java

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package org.eclipse.jgit.storage.dht.spi;

/**
 * A distributed database implementation.
 * <p>
 * A DHT provider must implement this interface to return table references for
 * each of the named tables. The database and the tables it returns are held as
 * singletons, and thus must be thread-safe. If the underlying implementation
 * needs to use individual "connections" for each operation, it is responsible
 * for setting up a connection pool, borrowing and returning resources within
 * each of the table APIs.
 * <p>
 * Most APIs on the tables are asynchronous and must perform their computation
 * in the background using a different thread than the caller. Implementations
 * that have only an underlying synchronous API should configure and use an
 * {@link java.util.concurrent.ExecutorService} to perform computation in the
 * background on a thread pool.
 * <p>
 * Tables returned by these methods should be singletons, as the higher level
 * DHT implementation usually invokes these methods each time it needs to use a
 * given table. The suggested implementation approach is:
 *
 * <pre>
 * class MyDatabase implements Database {
 * 	private final RepositoryIndexTable rep = new MyRepositoryIndex();
 *
 * 	private final RefTable ref = new MyRefTable();
 *
 * 	public RepositoryIndexTable repositoryIndex() {
 * 		return rep;
 * 	}
 *
 * 	public RefTable ref() {
 * 		return ref;
 * 	}
 * }
 * </pre>
 */
public interface Database {
	/** @return a handle to the table listing known repositories. */
	public RepositoryIndexTable repositoryIndex();

	/** @return a handle to the table storing repository metadata. */
	public RepositoryTable repository();

	/** @return a handle to the table listing references in a repository. */
	public RefTable ref();

	/** @return a handle to the table listing known objects. */
	public ObjectIndexTable objectIndex();

	/** @return a handle to the table listing pack data chunks. */
	public ChunkTable chunk();

	/**
	 * Create a new WriteBuffer for the current thread.
	 * <p>
	 * Unlike other methods on this interface, the returned buffer <b>must</b>
	 * be a new object on every invocation. Buffers do not need to be
	 * thread-safe.
	 *
	 * @return a new buffer to handle pending writes.
	 */
	public WriteBuffer newWriteBuffer();
}