[TCM] Failover and switchover

[p7nov]

Product: Tarantool Cluster Manager
Since: TCM 1.1.0, Tarantool 3.0
Audience/target: all
Root document: new page in https://www.tarantool.io/en/doc/latest/reference/tooling/tcm/ (?)
SME: @ filonenko-mikhail

Details

From TCM 1.1.0 release description: "Мониторинг фейловера 3 и свитчовер (консистетное переключение лидера)"

https://github.com/tarantool/tarantool-cluster-manager/issues/1354

• For clusters that use supervised failovers (external failover coordinator instances to define leadership)
• New Failover page available from the Actions menu on cluster stateboard
• Failovers tab: list of running coordinators, their statuses and information
• Commands tab: a form to send command to a coordinator. Currently, one command is supported -- switch (switch master, the analog of tt cluster failover switch).
• Command format: YAML with three fields: command, new_master, timeout. Example:

  command: switch
  new_master: instance-002
  timeout: 30