User’s Guide / Tarantool Cartridge / Table of contents / Module cartridge.twophase
User’s Guide / Tarantool Cartridge / Table of contents / Module cartridge.twophase

Module cartridge.twophase

Module cartridge.twophase

Clusterwide configuration propagation two-phase algorithm.

(Added in v1.2.0-19)

Functions

patch_clusterwide (patch)

Edit the clusterwide configuration. Top-level keys are merged with the current configuration. To remove a top-level section, use patch_clusterwide{key = box.NULL} .

The function uses a two-phase commit algorithm with the following steps:

  1. Patches the current configuration.
  2. Validates topology on the current server.

III. Executes the preparation phase ( prepare_2pc ) on every server excluding expelled and disabled servers.

IV. If any server reports an error, executes the abort phase ( abort_2pc ). All servers prepared so far are rolled back and unlocked.

V. Performs the commit phase ( commit_2pc ). In case the phase fails, an automatic rollback is impossible, the cluster should be repaired manually.

Parameters:

Returns:

(boolean) true

Or

(nil)

(table) Error description

get_schema ()

Get clusterwide DDL schema.

(Added in v1.2.0-28)

Returns:

(string) Schema in YAML format

Or

(nil)

(table) Error description

set_schema (schema)

Apply clusterwide DDL schema.

(Added in v1.2.0-28)

Parameters:

  • schema: (string) in YAML format

Returns:

(string) The same new schema

Or

(nil)

(table) Error description

on_patch (trigger_new, trigger_old)

Set up trigger for for patch_clusterwide.

It will be executed before new new config applied.

If the parameters are (nil, old_trigger) , then the old trigger is deleted.

The trigger function is called with two argument: - conf_new ( ClusterwideConfig ) - conf_old ( ClusterWideConfig )

It is allowed to modify conf_new , but not conf_old . Return values are ignored. If calling a trigger raises an error, patch_clusterwide returns it as nil, err .

(Added in v2.1.0-4)

Parameters:

  • trigger_new: (function)
  • trigger_old: (function)

Usage:

local function inject_data(conf_new, _)
    local data_yml = yaml.encode({foo = 'bar'})
    conf_new:set_plaintext('data.yml', data_yml)
end)

twophase.on_patch(inject_data) -- set custom patch modifier trigger
twophase.on_patch(nil, inject_data) -- drop trigger

Local Functions

prepare_2pc (data)

Two-phase commit - preparation stage.

Validate the configuration and acquire a lock setting local variable and writing “config.prepare.yml” file. If the validation fails, the lock isn’t acquired and doesn’t have to be aborted.

Parameters:

  • data: (table) clusterwide config content

Returns:

(boolean) true

Or

(nil)

(table) Error description

commit_2pc ()

Two-phase commit - commit stage.

Back up the active configuration, commit changes to filesystem by renaming prepared file, release the lock, and configure roles. If any errors occur, configuration is not rolled back automatically. Any problem encountered during this call has to be solved manually.

Returns:

(boolean) true

Or

(nil)

(table) Error description

abort_2pc ()

Two-phase commit - abort stage.

Release the lock for further commit attempts.

Returns:

(boolean) true