instances.md

Instances

Each instance of application is started as <app_name>@<instance_name> systemd service. instance_name is inventory_hostname from Ansible inventory.

Instances are identified by aliases that are set equal to Ansible host names.

Restarting instances

Instance is restarted only if it's required to apply changes (instance configuration was changed or package was updated). However, instance restart can be forced or disabled by restarted flag. If this flag isn't set, role decides if instance should be restarted.

Expelling instances

To expel an instance from topology specify expelled: true. See topology doc for details

Instance config

Instance can be configured using the config variable. For specifying parameters that are common for all instances, use cartridge_defaults variable. These variables describe instance parameters that would be passed to cartridge configuration. It can contain cluster-specific or some application-specific parameters (can be parsed in application using the cartridge.argparse module).

Required parameters

advertise_uri is required for instance configuration. It must be specified in <host>:<port> format.

Forbidden parameters

alias, console_sock, pid_file, and workdir parameters are forbidden for an instance.

Instance alias will be set equal to instance name.

Note: in the default systemd unit file for Tarantool Cartridge applications, some instance parameters are set:

Environment=TARANTOOL_WORKDIR=/var/lib/tarantool/{app_name}.{instance_name}
Environment=TARANTOOL_CFG=/etc/tarantool/conf.d/
Environment=TARANTOOL_PID_FILE=/var/run/tarantool/${app_name}.{instance_name}.pid
Environment=TARANTOOL_CONSOLE_SOCK=/var/run/tarantool/${app_name}.{instance_name}.control

Managing dynamic box.cfg parameters without restart

Some box.cfg options are dynamic, it means that it can be changed without instance restarting. See parameters with "Dynamic: yes".

Role changes these parameters without restarting the instance. If other parameters are changed, needs_restart is set to true.

Note, that if restarted flag is set, instance will be restarted anyway without changing dynamic parameters in runtime. You can use this flag to force instance restarting.

Increasing memtx_memory in runtime

If you specified in config.memtx_memory value that increases current memtx_memory, this role will try to increase this value in runtime. In case of success instance wouldn't be restarted (if other parameters haven't been changed).

Note, that if restarted flag is set, instance will be restarted anyway without changing memtx_memory in runtime. You can use this flag to force instance restarting.