electrs/doc/cookie_deprecation.md

Deprecation of cookie option

What?

As of 0.8.8 the cookie option is deprecated and it will be removed. A new auth option was added. If you don't use the cookie option, you're not affected and don't need to read this. Note that this is different from cookie_file.

Why?

The option was confusing:

• If you entered the path to cookie file (usually ~/.bitcoin/.cookie), it wouldn't work.
• If you copied the contents of cookie file into it, electrs would break at the next restart of the system.
• If you used a script to fix the above run before electrs starts, it'd still break if bitcoind restarted for any reason.
• If you used BindsTo option of systemd, you'd solve the issue but introduce needless downtime and waste of performance.
• Entering username:password was the only valid use of cookie but it had nothing to do with cookie.

What to do?

If you're installing electrs for the first time, just don't use cookie. If you're updating, reconsider the motivation above. If you used copying script, just use cookie_file to get the cookie directly. If you also used BindsTo, we recommend removing it. If you used fixed username and password because you didn't know about cookie or did it before cookie_file was implemented, reconsider using cookie authentication. If you really have to use fixed username and password, specify them using auth option (username:password like before) and remove the cookie option.

When the option will be removed?

Probably in a few months. It'll still be detected and turned into explicit error for a while to make sure people really see the message and know what's going on. You can see the tracking issue #371 to monitor the progress of the change.