[IO-598] FileUtils.moveFile should support atomic file replacement; introduce FileUtils.renameTo to force target file replacement?

• Type: Improvement
• Status: Closed
• Priority: Trivial
• Resolution: Information Provided
• Assignee: Unassigned
• Reporter: Mark
• Created: 07/Feb/19 15:17
• Updated: 25/Apr/23 20:34
• Resolved: 25/Apr/23 20:34

Description

Looking at current openjdk (11) source code, the regular File.rename() method calls the standard native rename function on UNIX-like systems. At least on Linux, this allows me to (atomically?) replace a file with another one, ie. without deleting the target file first.

 

FileUtils.moveFile however, throws an exception in case the target file alrady exists.

 

Here is the code bloat I currently use to rename-overwrite a file (and which I want to get rid of):

             // try to rename atomically first
            try {
                if (!tempFile.renameTo(mdFile)) {
                    throw new IOException();
                }
            } catch (Exception ex) {
                // then explicitly delete the target file first
                if (mdFile.exists()) {
                    mdFile.delete();
                }
                if (!tempFile.renameTo(mdFile)) {
                    throw new IOException("failed to rename " + tempFile + " to " + mdFile);
                }
            }

Can we please have a function that force-fully replaces existing target files, first atomically, then falling back to delete and move? Maybe call it FileUtils.forceRenameTo and don't delete target directories, only target files.

It could be simply a modification of the existing moveFile function: remove check for existing target, check and throw exception only if it is a directory. Then, upon moving, catch the exception and check if it could be due to existing target file. If so, retry after manually removing the target file.

Also, having a function with proper fsync support would be nice in that context: https://stackoverflow.com/questions/7433057/is-rename-without-fsync-safe

FielUtils.syncRenameTo?