multiple instances of emacs overwrite recentf-list

Question

I have quite usual recentf config.

(use-package recentf
  :config
  (setq
    recentf-save-file "~/.cache/emacs/recentf"
    recentf-max-saved-items 100000
    recentf-max-menu-items 5000
    )
  (recentf-mode 1)

The problem is that I run multiple emacs instances. Unfortunately, it overwrites recentf file when the instances are closed.

instance 1 loads recentf version 1
instance 2 loads recentf version 1
... some times passed instance 1 and instance 2 do some work ...
instance 1 get closed and saves recentf version 3
instance 2 get closed and saves recentf version 4

Problem is that when instance 2 closes it does not read recentf of version 3. As a result files added by version 3 are lost. You can imagine it gets worst with more than one instance. How can I make recentf work correctly with multiple instaces.

Answer 1

In case anybody still encounters this issue:

Try the sync-recentf package. I have not used it but it looks like what you want.

---

Every Emacs instance maintains the variable recentf-list which is populated by calling recentf-load-list. Opening files will then append the new filepath to this variable but not to the file. Calling recentf-save-list will then cause this variable to be written to the recentf-file you specified. Note that this writing out is not appending to the file but rather replacing its content.

Simply calling recentf-load-list before saving is not an option either because this will override the unique files from the recentf-list.

The aforementioned package works around this limitation by creating a dummy file on top of recentf-list effectively seperating this variable into 'old and new'. When calling recentf-save-list a new recentf-list is created by the following steps:

1. Save the new filepaths
2. Override recentf-list with the values from recentf-file
3. Append saved filepaths to recentf-list
4. Override recentf-file with the values from `recentf-list