Users can't be authenticated for _session - authentication

Question

I'm facing a very odd problem that I can't use any user inside (_users) database to create a session through the route (/_session). It's always giving me error (bad credentials). It used to work fine in couchdb 1.6.1
For normal couchdb adminstrators, it works fine :
$ curl -X POST http://localhost:5984/_session -d 'name=my_main_admin&password=******'
{"ok":true,"name":"my_main_admin","roles":["_admin"]}
However for couchdb users (stored in _users), it doesn't work. I don't think it's about the roles.
So I first create the user :
$ curl -s -H "Content-Type: application/json" -X PUT "http://my_main_admin:*****#127.0.0.1:5984/_node/_local/_users/org.couchdb.user:my_new_user" --data '{"name": "my_new_user", "password": "my_new_user", "roles": [], "type": "user"}'
{"ok":true,"id":"org.couchdb.user:my_new_user","rev":"1-f1fa0870666d17d7324e54128dfbcacb"}
Then if I try to use this user to create a session, it never works :
$ curl -X POST http://localhost:5984/_session -d 'name=my_new_user&password=my_new_user'
{"error":"unauthorized","reason":"Name or password is incorrect."}
My CouchDB config looks fine :
"couch_httpd_auth": {
"allow_persistent_cookies": "true",
"auth_cache_size": "50",
"authentication_db": "_users",
"authentication_redirect": "/_utils/session.html",
"iterations": "10",
"require_valid_user": "false"
I used to create sessions with normal users on couchdb 1.6.1 , but it has never worked since I installed couchdb 3.1.1 . I can't find any relevant info in the documentation.
Am I missing something?

Answer 1

The problem is that you are creating the user through the _node/_local interface. The user should be created via the clustered API on the _users clustered database.
$ curl -s -H "Content-Type: application/json" -X PUT \
"http://my_main_admin:*****#127.0.0.1:5984/_users/org.couchdb.user:my_new_user" \
--data '{"name": "my_new_user", "password": "my_new_user", "roles": [], "type": "user"}' \
/
Now you should be able to log in with the new user using the _session endpoint.