tarantoolscript/src/builtin/box/cfg/ConfigHotStandby.d.ts

TypeScript definitions for Tarantool Lua API.

export interface ConfigHotStandby {
  /**
   * Since version 1.7.4. Whether to start the server in hot standby mode.
   *
   * Hot standby is a feature which provides a simple form of failover without replication.
   *
   * The expectation is that there will be two instances of the server using the same configuration.
   * The first one to start will be the “primary” instance. The second one to start will be the “standby” instance.
   *
   * To initiate the standby instance, start a second instance of the Tarantool server on the same computer
   * with the same box.cfg configuration settings – including the same directories and same non-null URIs –
   * and with the additional configuration setting `hot_standby = true`.
   * Expect to see a notification ending with the words `I> Entering hot standby mode`. This is fine.
   * It means that the standby instance is ready to take over if the primary instance goes down.
   *
   * The standby instance will initialize and will try to take a lock on wal_dir,
   * but will fail because the primary instance has made a lock on `wal_dir`.
   * So the standby instance goes into a loop, reading the write ahead log which the primary instance is writing
   * (so the two instances are always in sync), and trying to take the lock.
   * If the primary instance goes down for any reason, the lock will be released.
   * In this case, the standby instance will succeed in taking the lock,
   * will connect on the listen address and will become the primary instance.
   * Expect to see a notification ending with the words `I> ready to accept requests`.
   *
   * Thus there is no noticeable downtime if the primary instance goes down.
   *
   * Hot standby feature has no effect:
   *
   * - if `wal_dir_rescan_delay = a large number` (on Mac OS and FreeBSD); on these platforms, it is designed so that the loop repeats every wal_dir_rescan_delay seconds.
   * - if `wal_mode = ‘none’`; it is designed to work with wal_mode = 'write' or wal_mode = 'fsync'.
   * - for spaces created with `engine = ‘vinyl’`; it is designed to work for spaces created with `engine = 'memtx'`.
   */
  hot_standby?: boolean,
}