How does a FileLock work over the network? Will it only lock a local file in the mount, or will the lock "propagate" to the file on another machine?

Question

Okay, so I'm unsure how mounts over a network work with file locks.

This is the scenario:

There are two JVMs, each running on a machine of its own (both Linux).

Then there is a file share, on a third machine (Windows).

Both the machines running a JVM each have mounted the same windows fileshare using CIFS/SAMBA.

If JVM-1 takes a lock on a file, using the FileLocker from Spring Integration for example, in its "local network mount" (or however to phrase it), will JVM-2 recognise that lock?

Or will the lock only be taken on that file local to the Linux machine, even though it is network share mounted and is bound somehow to a file on the Windows machine?

Answer 1

The NIOFileLocker essentially works properly only on Windows. It doesn't matter how you mount that remote Windows dir, you stil work from Linux. Moreover you said it yourself: you deal with files via SMB protocol - nothing about local filesystem where NIOFileLocker would have an effect.

See Spring Integration SMB support: https://docs.spring.io/spring-integration/docs/current/reference/html/smb.html#smb and consider to use an SmbPersistentAcceptOnceFileListFilter based on some shared persistent DB: https://docs.spring.io/spring-integration/docs/current/reference/html/meta-data-store.html#metadata-store. The filter will look into the store to check if file has been already processed in some other instance. This is essentially a distributed file locking you are looking for.