Locking Support in MapR

MapR Filesystem does not support server-side locking. This means that locks are held by components outside of the file system layer and hence not shared or enforced globally. As a result, when locking is available, you will need to carefully understand exactly where this enforcement occurs and ensure that all programs using the same locks access them through the same enforcement point. Also, locks, when supported in MapR, are always whole file locks and advisory, not mandatory. The following table describes the locking support in MapR for the clients.

Client Type Locking Support Default Value Notes
Hadoop No N/A Hadoop does not support locking APIs.
FUSE-based POSIX Yes Lock MapR supports advisory locking using kernel locking. This lock is locally enforced on that single Linux host and not shared with other hosts. The lock is only meaningful if all users accessing the file are using FUSE and are on the same host.
Loopback NFS POSIX No N/A No support in MapR for locking. However, you can use Network Lock Manager to lock with the nolock option on the mount command. This lock is locally enforced on that single Linux host and not shared with other hosts. The lock is only meaningful if all lock users are using loopbacknfs and are on the same host.
NFSv3 No N/A No support for locking in MapR. However, you can use Network Lock Manager to lock with the nolock option on the mount command. This lock is locally enforced on that single Linux host and not shared with other hosts. The lock is only meaningful if all lock users are using NFSv3 and are on the same host.
NFSv4 Yes NoLock MapR supports advisory locking for NFSv4 server. This is locally enforced on NFSv4 server, which means the lock is only meaningful if all lock users are using the same NFSv4 server. See Advisory Locking in NFSv4 for more information.