config: compat options

[TarantoolBot]

Related dev. issue(s): tarantool/tarantool#9497
Duplicate: #4021

Product: Tarantool
Since: 3.0
Root document:

• A new compat section in the Configuration reference. Each option can have a short description with a link to a corresponding page in Module compat.

SME: @ Totktonada

Details

The new section compat is added to the declarative configuration.

The options are the same as ones provided by the compat module. Each
can be set to old or new.

Example:

compat:
  json_escape_forward_slash: old

The list of currently supported options with their defaults:

compat:
  json_escape_forward_slash: new
  yaml_pretty_multiline: new
  fiber_channel_close_mode: new
  box_cfg_replication_sync_timeout: new
  sql_seq_scan_default: new
  fiber_slice_default: new
  box_info_cluster_meaning: new
  binary_data_decoding: new
  box_tuple_new_vararg: new
  box_session_push_deprecation: old
  sql_priv: new
  c_func_iproto_multireturn: new
  box_space_execute_priv: new
  box_tuple_extension: new
  box_space_max: new
...

The box_cfg_replication_sync_timeout option is non-dynamic and it
can't be changed after a startup.

Technically, all the other options could be changed in runtime (by
changing the configuration file and calling config:reload()), but I
would not generally recommend it.

At least code that handles fiber_channel_close_mode option has the
following comment, see commit de9b93081873 ("fiber: add channel close
mode option to compat").

The behavior is unspecified for already created channels.
Choose the mode at an early stage of application's
initialization.

Requested by @ Totktonada in tarantool/tarantool@317dc03.