[3pt] Set box.cfg options via environment variables

[TarantoolBot]

Set box.cfg options via environment variables

Product: Tarantool
Since: 2.8.1
Audience/target: all Tarantool users
Root document:

• https://www.tarantool.io/en/doc/latest/reference/configuration/#box-cfg-params (most probably -- to create a new section to describe this way of setting box.cfg options)
• https://www.tarantool.io/en/doc/latest/release/2.8.1

SME: @ romanhabibov

Details

1. Now, it is possible to set box.cfg options via environment variables.
   The name of variable should correspond the following pattern:
   TT_<NAME>, where <NAME> is uppercase box.cfg option name. For
   example: TT_LISTEN, TT_READAHEAD.

Array values are separated by comma. Example:

export TT_REPLICATION=localhost:3301,localhost:3302

An empty variable is the same as unset one.

2. When Tarantool instance is
   started under tarantoolctl utility, environment variables have higher
   priority than tarantoolctl configuration file.

• Related development issues and/or commits: tarantool/tarantool@1b33012

Definition of done

• Possiblity of setting box.cfg options via environment variables is described.
• Add info about priorities of the config parameters' sources
• Add cross-references with the release 2.8.1 page

[NickVolynkin]

https://12factor.net/config

[NickVolynkin]

For an example of variable precedence, see https://docs.ansible.com/ansible/latest/user_guide/playbooks_variables.html#variable-precedence-where-should-i-put-a-variable