Monitoring: getting started

Tarantool

First, you need to install the metrics package:

$ cd ${PROJECT_ROOT}
$ tarantoolctl rocks install metrics

Next, require it in your code:

local metrics = require('metrics')

Set a global label for your metrics:

metrics.set_global_labels({alias = 'alias'})

Enable default Tarantool metrics such as network, memory, operations, etc:

metrics.enable_default_metrics()

If you use Cartridge, enable Cartridge metrics:

metrics.enable_cartridge_metrics()

Initialize the Prometheus Exporter, or export metrics in any other format:

local httpd = require('http.server')
local http_handler = require('metrics.plugins.prometheus').collect_http


httpd.new('0.0.0.0', 8088)
    :route({path = '/metrics'}, function(...)
        return http_handler(...)
end)
    :start()

box.cfg{
    listen = 3302
}

Now you can use the HTTP API endpoint /metrics to collect your metrics in the Prometheus format. If you need your custom metrics, see the API reference.

Instance health check

In production environments Tarantool Cluster usually has a large number of so called «routers», Tarantool instances that handle input load and it is required to evenly distribute the load. Various load-balancers are used for this, but any load-balancer have to know which «routers» are ready to accept the load at that very moment. Metrics library has a special plugin that creates an http handler that can be used by the load-balancer to check the current state of any Tarantool instance. If the instance is ready to accept the load, it will return a response with a 200 status code, if not, with a 500 status code.

Cartridge role

cartridge.roles.metrics is a role for Tarantool Cartridge. It allows using default metrics in a Cartridge application and manage them via configuration.

Usage

Add metrics package to dependencies in the .rockspec file. Make sure that you are using version 0.3.0 or higher.
```
dependencies = {
    ...
    'metrics >= 0.3.0-1',
    ...
}
```

Make sure that you have cartridge.roles.metrics in the roles list in cartridge.cfg in your entry-point file (e.g. init.lua).

local ok, err = cartridge.cfg({
    ...
    roles = {
        ...
        'cartridge.roles.metrics',
        ...
    },
})

To view metrics via API endpoints, use set_export.

NOTE that set_export has lower priority than clusterwide config and could be overriden by the metrics config.

local metrics = require('cartridge.roles.metrics')
metrics.set_export({
    {
        path = '/path_for_json_metrics',
        format = 'json'
    },
    {
        path = '/path_for_prometheus_metrics',
        format = 'prometheus'
    },
    {
        path = '/health',
        format = 'health'
    }
})

You can add several entry points of the same format by different paths, like this:

metrics.set_export({
    {
        path = '/path_for_json_metrics',
        format = 'json'
    },
    {
        path = '/another_path_for_json_metrics',
        format = 'json'
    },
})

The metrics will be available on the path specified in path in the format specified in format.

Enable role in the interface:

Since version 0.6.0 metrics role is permanent and enabled on instances by default.
After role initialization, default metrics will be enabled and the global label 'alias' will be set. Note that 'alias' label value is set by instance configuration option alias or instance_name (since 0.6.1).

If you need to use the functionality of any metrics package, you may get it as a Cartridge service and use it like a regular package after require:
```
local cartridge = require('cartridge')
local metrics = cartridge.service_get('metrics')
```
There is an ability in Tarantool Cartridge >= '2.4.0' to set a zone for each server in cluster. If zone was set for the server 'zone' label for all metrics of this server will be added.

To change metrics HTTP path in runtime, you may use the following configuration (to learn more about Cartridge configuration, see this). We don’t recommend to use it to set up metrics role, use set_export instead.

metrics:
  export:
  - path: '/path_for_json_metrics'
    format: 'json'
  - path: '/path_for_prometheus_metrics'
    format: 'prometheus'
  - path: '/health'
    format: 'health'

To set custom global labels, you may use the following configuration.

metrics:
  export:
  - path: '/metrics'
    format: 'json'
  global-labels:
    my-custom-label: label-value

OR use set_labels function in init.lua.

local metrics = require('cartridge.roles.metrics')
metrics.set_labels({ ['my-custom-label'] = 'label-value'} )