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I have 2 machines both running one process each. shell process on Machine A will scp something to machine B, and java process on B will use these files. Both processes run as crontab tasks.
How to achieve synchronization/atomicity etc? How to signal that whole of file has been written.
so that process on B always has access to latest and complete files, the handler doesn’t go stale..
Assuming you’re using a filesystem with atomic moves you can do that. Or use symbolic links.
A copies the file to a temp location on B. When the upload is complete, it relocates, with a move or symlink, the file into the expected location. B can then only ever see completely uploaded files.
If your process on A cannot SSH into B to make the final move, it could rather add another, zero byte marker file which indicates the upload is complete.
A uploads FOO.txt, when that upload is complete, it creates the FOO.txt.done file. B then scans the directory for *.done files, and uses the associated data file. Plus cleanup of course.