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Metrics instrumentation guide
This guide describes how to develop Usage Ping metrics using metrics instrumentation.
Nomenclature
-
Instrumentation class:
- Inherits one of the metric classes:
DatabaseMetric
,RedisHLLMetric
orGenericMetric
. - Implements the logic that calculates the value for a Usage Ping metric.
- Inherits one of the metric classes:
-
Metric definition The Usage Data metric YAML definition.
-
Hardening: Hardening a method is the process that ensures the method fails safe, returning a fallback value like -1.
How it works
A metric definition has the instrumentation_class
field, which can be set to a class.
The defined instrumentation class should have one of the existing metric classes: DatabaseMetric
, RedisHLLMetric
, or GenericMetric
.
Using the instrumentation classes ensures that metrics can fail safe individually, without breaking the entire process of Usage Ping generation.
We have built a domain-specific language (DSL) to define the metrics instrumentation.
Database metrics
Example of a merge request that adds a database metric.
module Gitlab
module Usage
module Metrics
module Instrumentations
class CountBoardsMetric < DatabaseMetric
operation :count
relation { Board }
end
end
end
end
end
Redis HyperLogLog metrics
Example of a merge request that adds a RedisHLL
metric.
Count unique values for i_quickactions_approve
event.
time_frame: 28d
data_source: redis_hll
instrumentation_class: 'Gitlab::Usage::Metrics::Instrumentations::RedisHLLMetric'
options:
events:
- i_quickactions_approve
Generic metrics
Example of a merge request that adds a generic metric.
module Gitlab
module Usage
module Metrics
module Instrumentations
class UuidMetric < GenericMetric
value do
Gitlab::CurrentSettings.uuid
end
end
end
end
end
end
Creating a new metric instrumentation class
To create a stub instrumentation for a Usage Ping metric, you can use a dedicated generator:
The generator takes the class name as an argument and the following options:
--type=TYPE
Required. Indicates the metric type. It must be one of:database
,generic
,redis_hll
.--ee
Indicates if the metric is for EE.
rails generate gitlab:usage_metric CountIssues --type database
create lib/gitlab/usage/metrics/instrumentations/count_issues_metric.rb
create spec/lib/gitlab/usage/metrics/instrumentations/count_issues_metric_spec.rb