Optimistic vs Pessimistic concurrency: when locking is good

OrientDB has an optimistic concurrency control system, but on very high concurrent updates on the few records it could be more efficient locking records to avoid retries. You could synchronize the access by yourself or by using the storage API. Note that this works only with non-remote databases.

((OStorageEmbedded)db.getStorage()).acquireWriteLock(final ORID iRid)
((OStorageEmbedded)db.getStorage()).acquireSharedLock(final ORID iRid)
((OStorageEmbedded)db.getStorage()).releaseWriteLock(final ORID iRid)
((OStorageEmbedded)db.getStorage()).releaseSharedLock(final ORID iRid)

Example of usage. Writer threads:

try{
  ((OStorageEmbedded)db.getStorage()).acquireWriteLock(record.getIdentity());

  // DO SOMETHING
} finally {
  ((OStorageEmbedded)db.getStorage()).releaseWriteLock(record.getIdentity());
}

Reader threads:

try{
  ((OStorageEmbedded)db.getStorage()).acquireSharedLock(record.getIdentity());
  // DO SOMETHING

} finally {
  ((OStorageEmbedded)db.getStorage()).releaseSharedLock(record.getIdentity());
}

For more information: 

https://github.com/orientechnologies/orientdb/wiki/Performance-Tuning#high-concurrency

Luca Garulli
CEO at Orient Technologies
the Company behind OrientDB
http://about.me/luca.garulli