[3pt] box.info.ro_reason

[TarantoolBot]

Product: Tarantool
Since: 2.10.0-beta2
Audience/target: Tarantool users
Root document: https://www.tarantool.io/en/doc/latest/reference/reference_lua/box_info/
SME: @ Gerold103

Related to #2444
Has a follow-up in #2953

Details

The new box.info field - ro_reason - is nil on a writable
instance. On a read-only instance box.info.ro == true it reports
an error reason. Currently the list is

• 'election' - box.cfg.election_mode is not 'off' and this
  instance is not a leader. See box.info.election for details.
• 'synchro' - the synchro queue is owned by some other instance.
  For details see box.info.synchro.
• 'config' - box.cfg.read_only is true;
• 'orphan' - the instance is in orphan state.
  Requested by @Gerold103 in tarantool/tarantool@48185e8

ToDo

• - Mention the new field in the list on the main page https://www.tarantool.io/en/doc/latest/reference/reference_lua/box_info/

• Create a child page for the box.info.ro_reason and put the description of the reasons there

• Make cross-reference to the description of the error_object.reason (see box.error.READONLY new attributes #2444)

• Don't forget about the follow-up of the topic in ER_READONLY error receives new reasons #2953