Server introspection¶
Using Tarantool as a client¶
Tarantool enters the interactive mode if:
- you start Tarantool without an instance file, or
- the instance file contains console.start().
Tarantool displays a prompt (e.g. “tarantool>”) and you can enter requests. When used this way, Tarantool can be a client for a remote server. See basic examples in Getting started.
The interactive mode is used by tarantoolctl to implement “enter” and
“connect” commands.
Executing code on an instance¶
You can attach to an instance’s admin console and execute some Lua code using
tarantoolctl:
$ # for local instances:
$ tarantoolctl enter my_app
/bin/tarantoolctl: Found my_app.lua in /etc/tarantool/instances.available
/bin/tarantoolctl: Connecting to /var/run/tarantool/my_app.control
/bin/tarantoolctl: connected to unix/:/var/run/tarantool/my_app.control
unix/:/var/run/tarantool/my_app.control> 1 + 1
---
- 2
...
unix/:/var/run/tarantool/my_app.control>
$ # for local and remote instances:
$ tarantoolctl connect username:password@127.0.0.1:3306
You can also use tarantoolctl to execute Lua code on an instance without
attaching to its admin console. For example:
# executing commands directly from the command line
$ <command> | tarantoolctl eval my_app
<...>
$ # - OR -
# executing commands from a script file
$ tarantoolctl eval my_app script.lua
<...>
Note
Alternatively, you can use the console module or the
net.box module from a Tarantool server. Also, you can
write your client programs with any of the
connectors. However, most of the examples in
this manual illustrate usage with either tarantoolctl connect or
using the Tarantool server as a client.
Health checks¶
To check the instance status, say:
$ tarantoolctl status my_app
my_app is running (pid: /var/run/tarantool/my_app.pid)
$ # - OR -
$ systemctl status tarantool@my_app
tarantool@my_app.service - Tarantool Database Server
Loaded: loaded (/etc/systemd/system/tarantool@.service; disabled; vendor preset: disabled)
Active: active (running)
Docs: man:tarantool(1)
Process: 5346 ExecStart=/usr/bin/tarantoolctl start %I (code=exited, status=0/SUCCESS)
Main PID: 5350 (tarantool)
Tasks: 11 (limit: 512)
CGroup: /system.slice/system-tarantool.slice/tarantool@my_app.service
+ 5350 tarantool my_app.lua <running>
To check the boot log, on systems with systemd, say:
$ journalctl -u tarantool@my_app -n 5
-- Logs begin at Fri 2016-01-08 12:21:53 MSK, end at Thu 2016-01-21 21:17:47 MSK. --
Jan 21 21:17:47 localhost.localdomain systemd[1]: Stopped Tarantool Database Server.
Jan 21 21:17:47 localhost.localdomain systemd[1]: Starting Tarantool Database Server...
Jan 21 21:17:47 localhost.localdomain tarantoolctl[5969]: /usr/bin/tarantoolctl: Found my_app.lua in /etc/tarantool/instances.available
Jan 21 21:17:47 localhost.localdomain tarantoolctl[5969]: /usr/bin/tarantoolctl: Starting instance...
Jan 21 21:17:47 localhost.localdomain systemd[1]: Started Tarantool Database Server
For more details, use the reports provided by functions in the following submodules:
- box.cfg submodule (check and specify all configuration parameters for the Tarantool server)
- box.slab submodule (monitor the total use and fragmentation of memory allocated for storing data in Tarantool)
- box.info submodule (introspect Tarantool server variables, primarily those related to replication)
- box.stat submodule (introspect Tarantool request and network statistics)
You can also try tarantool/prometheus, a Lua module that makes it easy to collect metrics (e.g. memory usage or number of requests) from Tarantool applications and databases and expose them via the Prometheus protocol.
Example
A very popular administrator request is box.slab.info(), which displays detailed memory usage statistics for a Tarantool instance.
tarantool> box.slab.info()
---
- items_size: 228128
items_used_ratio: 1.8%
quota_size: 1073741824
quota_used_ratio: 0.8%
arena_used_ratio: 43.2%
items_used: 4208
quota_used: 8388608
arena_size: 2325176
arena_used: 1003632
...