Starting and stopping instances

This section describes how to manage instances in a Tarantool cluster using the tt utility. A cluster can include multiple instances that run different code. A typical example is a cluster application that includes router and storage instances. Particularly, you can perform the following actions:

• start all instances in a cluster or only specific ones
• check the status of instances
• connect to a specific instance
• stop all instances or only specific ones

To get more context on how the application's environment might look, refer to Application environment.

To start Tarantool instances use the tt start command:

 
$ tt start sharded_cluster_crud   • Starting an instance [sharded_cluster_crud:storage-a-001]...   • Starting an instance [sharded_cluster_crud:storage-a-002]...   • Starting an instance [sharded_cluster_crud:storage-b-001]...   • Starting an instance [sharded_cluster_crud:storage-b-002]...   • Starting an instance [sharded_cluster_crud:router-a-001]...

After the cluster has started and worked for some time, you can find its artifacts in the directories specified in the tt configuration. These are the default locations in the local launch mode:

• sharded_cluster_crud/var/log/<instance_name>/ – instance logs.
• sharded_cluster_crud/var/lib/<instance_name>/ – snapshots and write-ahead logs.
• sharded_cluster_crud/var/run/<instance_name>/ – control sockets and PID files.

In the system launch mode, artifacts are created in these locations:

• /var/log/tarantool/<instance_name>/
• /var/lib/tarantool/<instance_name>/
• /var/run/tarantool/<instance_name>/

Most of the commands described in this section can be called with or without an instance name. Without the instance name, they are executed for all instances defined in instances.yaml.

To check the status of instances, execute tt status:

 
$ tt status sharded_cluster_crud INSTANCE                            STATUS   PID   MODE  CONFIG  BOX      UPSTREAM sharded_cluster_crud:router-a-001   RUNNING  8382  RW    ready   running  -- sharded_cluster_crud:storage-a-001  RUNNING  8386  RW    ready   running  -- sharded_cluster_crud:storage-a-002  RUNNING  8390  RO    ready   running  -- sharded_cluster_crud:storage-b-001  RUNNING  8379  RW    ready   running  -- sharded_cluster_crud:storage-b-002  RUNNING  8380  RO    ready   running  --

To check the status of a specific instance, you need to specify its name:

 
$ tt status sharded_cluster_crud:storage-a-001 INSTANCE                            STATUS   PID   MODE  CONFIG  BOX      UPSTREAM sharded_cluster_crud:storage-a-001  RUNNING  8386  RW    ready   running  --

To connect to the instance, use the tt connect command:

 
$ tt connect sharded_cluster_crud:storage-a-001   • Connecting to the instance...   • Connected to sharded_cluster_crud:storage-a-001sharded_cluster_crud:storage-a-001>

In the instance's console, you can execute commands provided by the box module. For example, box.info can be used to get various information about a running instance:

 
sharded_cluster_crud:storage-a-001> box.info.ro---- false...

To restart an instance, use tt restart:

 
$ tt restart sharded_cluster_crud:storage-a-002

After executing tt restart, you need to confirm this operation:

 
Confirm restart of 'sharded_cluster_crud:storage-a-002' [y/n]: y   • The Instance sharded_cluster_crud:storage-a-002 (PID = 2026) has been terminated.   • Starting an instance [sharded_cluster_crud:storage-a-002]...

To stop the specific instance, use tt stop as follows:

 
$ tt stop sharded_cluster_crud:storage-a-002

You can also stop all the instances at once as follows:

 
$ tt stop sharded_cluster_crud   • The Instance sharded_cluster_crud:storage-b-001 (PID = 2020) has been terminated.   • The Instance sharded_cluster_crud:storage-b-002 (PID = 2021) has been terminated.   • The Instance sharded_cluster_crud:router-a-001 (PID = 2022) has been terminated.   • The Instance sharded_cluster_crud:storage-a-001 (PID = 2023) has been terminated.   • can't "stat" the PID file. Error: "stat /home/testuser/myapp/instances.enabled/sharded_cluster_crud/var/run/storage-a-002/tt.pid: no such file or directory"

The tt clean command removes instance artifacts (such as logs or snapshots):

 
$ tt clean sharded_cluster_crud   • List of files to delete:   • /home/testuser/myapp/instances.enabled/sharded_cluster_crud/var/log/storage-a-001/tt.log   • /home/testuser/myapp/instances.enabled/sharded_cluster_crud/var/lib/storage-a-001/00000000000000001062.snap   • /home/testuser/myapp/instances.enabled/sharded_cluster_crud/var/lib/storage-a-001/00000000000000001062.xlog   • ...Confirm [y/n]:

Enter y and press Enter to confirm removing of artifacts for each instance.

Tarantool supports loading and running chunks of Lua code before starting instances. To load or run Lua code immediately upon Tarantool startup, specify the TT_PRELOAD environment variable. Its value can be either a path to a Lua script or a Lua module name:

• To run the Lua script preload_script.lua from the sharded_cluster_crud directory, set TT_PRELOAD as follows:

   
  $ TT_PRELOAD=preload_script.lua tt start sharded_cluster_crud

  Tarantool runs the preload_script.lua code, waits for it to complete, and then starts instances.

• To load the preload_module from the sharded_cluster_crud directory, set TT_PRELOAD as follows:

   
  $ TT_PRELOAD=preload_module tt start sharded_cluster_crud

To load several scripts or modules, pass them in a single quoted string, separated by semicolons:

 
$ TT_PRELOAD="preload_script.lua;preload_module" tt start sharded_cluster_crud

If an error happens during the execution of the preload script or module, Tarantool reports the problem and exits.