Tutorial: Module compat
This tutorial covers the following compat module API and its usage:
The options list is serialized in the interactive console with additional details for user convenience:
- All non-obsolete options in order new > old > default.
- Serialization returns array-like table with tables
{<option> = <value>}. - The result of compat serialization can still be indexed as a normal key-value table.
tarantool> compat = require('compat')
---
...
tarantool> compat
---
- - json_escape_forward_slash: new
- - option_2: old
- - option_default_old: default (old)
- - option_default_new: default (new)
...
current– the state of the option.default– the default state of the option.brief– text options description with a link to more detailed description.
tarantool> compat.option_default_new
---
- current: old
default: new
brief: <...>
...
You can do it directly, or by passing a table with option-value. Possible values to assign are „new“ , „old“, and „default“.
tarantool> compat.json_escape_forward_slash = 'old'
---
...
tarantool> compat{json_escape_forward_slash = 'new', option_2 = 'default'}
---
...
By setting „default“ value to an option:
tarantool> compat.option_2 = 'default'
---
...
tarantool> compat.option_2
---
- current: default
- default: new
- brief: <...>
...
tarantool> compat({
> obsolete_set_explicitly = 'new',
> option_set_old = 'old',
> option_set_new = 'new'
> })
---
...
tarantool> compat
---
- - option_set_old: old
- - option_set_new: new
- - option_default_old: default (old)
- - option_default_new: default (new)
...
# Obsolete options are not returned in serialization, but have the following values:
# - obsolete_option_default: default (new)
# - obsolete_set_explicitly: new
# nil does output obsolete unset options as 'default'
tarantool> compat.dump()
---
- require('compat')({
option_set_old = 'old',
option_set_new = 'new',
option_default_old = 'default',
option_default_new = 'default',
obsolete_option_default = 'default', -- obsolete since X.Y
obsolete_set_explicitly = 'new', -- obsolete since X.Y
})
...
# 'current' is the same as nil with default set to current values
tarantool> compat.dump('current')
---
- require('compat')({
option_set_old = 'old',
option_set_new = 'new',
option_default_old = 'old',
option_default_new = 'new',
obsolete_option_default = 'new', -- obsolete since X.Y
obsolete_set_explicitly = 'new', -- obsolete since X.Y
})
...
# 'new' outputs obsolete as 'new'.
tarantool> compat.dump('new')
---
- require('compat')({
option_set_old = 'new',
option_set_new = 'new',
option_default_old = 'new',
option_default_new = 'new',
obsolete_option_default = 'new', -- obsolete since X.Y
obsolete_set_explicitly = 'new', -- obsolete since X.Y
})
...
# 'old' outputs obsolete options as 'new'.
tarantool> compat.dump('old')
---
- require('compat')({
option_set_old = 'old',
option_set_new = 'old',
option_default_old = 'old',
option_default_new = 'old',
obsolete_option_default = 'new', -- obsolete since X.Y
obsolete_set_explicitly = 'new', -- obsolete since X.Y
})
...
# 'default' does output obsolete options as default.
tarantool> dump('default')
---
- require('compat')({
option_set_old = 'default',
option_set_new = 'default',
option_default_old = 'default',
option_default_new = 'default',
obsolete_option_default = 'default', -- obsoleted since X.Y
obsolete_set_explicitly = 'default', -- obsoleted since X.Y
})
...
- use compat.dump() to get a specific configuration
- copy and paste it into console (or use loadstring())
tarantool> compat.dump('new')
---
- require('compat')({
option_2 = 'new',
json_escape_forward_slash = 'new',
})
...
tarantool> require('compat')({
option_2 = 'new',
json_escape_forward_slash = 'new',
})
---
...
tarantool> compat
---
- - json_escape_forward_slash: new
- - option_2: new
...
User must provide a table with:
- name (string)
- default (’new’ / ’old’)
- brief (explanation of the option, can be multiline string)
- obsolete (’X.Y’ / nil) — tarantool version that marked option as obsolete. When nil, option is treated as non-obsolete)
- action function (argument - boolean is_new, changes the behavior accordingly)
- run_action_now (true / false / nil) if add_options should run action afterwards, false by default
Option hot reload:
You can change an existing option in runtime using add_option(), it will update all the fields but keep currently selected behavior if any. The new action will be called afterwards.
tarantool> compat.add_option{
name = 'option_4',
default = 'new',
brief = "<...>",
obsolete = nil, -- you can explicitly mark the option as non-obsolete
action = function(is_new)
print(("option_4 action was called with is_new = %s!"):format(is_new))
end,
run_action_now = true
}
option_4 postaction was called with is_new = true!
---
...
tarantool> compat.add_option{ -- hot reload of option_4
name = 'option_4',
default = 'old', -- different default
brief = "<...>",
action = function(is_new)
print(("new option_4 action was called with is_new = %s!"):format(is_new))
end
}
---
... -- action is not called by default