Module Rotation

description of boundaries for file rotation.

If all fields are None the file will never be rotated. Any field set to Some will cause rotation to happen when that boundary is crossed. Multiple boundaries may be set. Log rotation always causes incrementing rotation conditions (e.g. size) to reset.

The condition keep is special and does not follow the rules above. When a log is rotated keep is examined and logs that do not fall under its instructions are deleted. This deletion takes place on rotation only, and so may not happen. The meaning of keep options are:

• `All -- never delete
• `Newer_than span -- delete files with a timestamp older than Time.sub (Time.now ()) span. This normally means keeping files that contain at least one message logged within span. If span is short enough this option can delete a just rotated file.
• `At_least i -- keep the i most recent files

Log rotation does not support symlinks, and you're encouraged to avoid them in production applications. Issues with symlinks:

• You can't tail symlinks without being careful (e.g. you must remember to pass "-F" to `tail`).
• Symlinks are hard to reason about when the program crashes, especially on startup (i.e., is the symlink pointing me at the right log file?).
• Atomicity is hard.
• Symlinks encourage tailing, which is a bad way to communicate information.
• They complicate archiving processes (the symlink must be skipped).