Sunday, January 15, 2012

Blob Store

In release 2.0-beta14 (I know, this is the late beta release) AliBaba introduced a new BLOB store. The blob store integrates with the RDF repository ObjectRepository to synchronize transactions. This allows both the BLOB store and the RDF store to be isolated and always consistent with one another. This is done using two-phase commit transactions in the BLOB store.

The BLOB store also has a few other advantages over a traditional file system. First every change is isolated until it is closed/committed. This prevents other readers from see an incomplete BLOB and help prevent inconsistency between the BLOB and RDF stores. In additional, as disk space is generally considered cheap, all past versions of BLOBs are keep on disk by default. This allows any previous versions to be retrieved (and restored) using the API.

The BLOB store API is fairly simple. Here what some code might look like using the BLOB store.

BlobStoreFactory factory = BlobStoreFactory.newInstance();
BlobStore store = factory.openBlobStore(new File("."));
String key = "";
BlobObject blob =;
OutputStream out = blob.openOutputStream();
try {
// write stream to out
} finally {
InputStream in = blob.openInputStream();
try {
// read stream from in
} finally {

More API options can be see in the JavaDocs: