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|
# frozen_string_literal: true
class PrometheusMetricsFinder
ACCEPTED_PARAMS = [
:project,
:group,
:title,
:y_label,
:identifier,
:id,
:common,
:ordered
].freeze
# Cautiously preferring a memoized class method over a constant
# so that the DB connection is accessed after the class is loaded.
def self.indexes
@indexes ||= PrometheusMetric
.connection
.indexes(:prometheus_metrics)
.map { |index| index.columns.map(&:to_sym) }
end
def initialize(params = {})
@params = params.slice(*ACCEPTED_PARAMS)
end
# @return [PrometheusMetric, PrometheusMetric::ActiveRecord_Relation]
def execute
validate_params!
metrics = by_project(::PrometheusMetric.all)
metrics = by_group(metrics)
metrics = by_title(metrics)
metrics = by_y_label(metrics)
metrics = by_common(metrics)
metrics = by_ordered(metrics)
metrics = by_identifier(metrics)
metrics = by_id(metrics)
metrics
end
private
attr_reader :params
def by_project(metrics)
return metrics unless params[:project]
metrics.for_project(params[:project])
end
def by_group(metrics)
return metrics unless params[:group]
metrics.for_group(params[:group])
end
def by_title(metrics)
return metrics unless params[:title]
metrics.for_title(params[:title])
end
def by_y_label(metrics)
return metrics unless params[:y_label]
metrics.for_y_label(params[:y_label])
end
def by_common(metrics)
return metrics unless params[:common]
metrics.common
end
def by_ordered(metrics)
return metrics unless params[:ordered]
metrics.ordered
end
def by_identifier(metrics)
return metrics unless params[:identifier]
metrics.for_identifier(params[:identifier])
end
def by_id(metrics)
return metrics unless params[:id]
metrics.id_in(params[:id])
end
def validate_params!
validate_params_present!
validate_id_params!
validate_indexes!
end
# Ensure all provided params are supported
def validate_params_present!
raise ArgumentError, "Please provide one or more of: #{ACCEPTED_PARAMS}" if params.blank?
end
# Protect against the caller "finding" the wrong metric
def validate_id_params!
raise ArgumentError, 'Only one of :identifier, :id is permitted' if params[:identifier] && params[:id]
raise ArgumentError, ':identifier must be scoped to a :project or :common' if params[:identifier] && !(params[:project] || params[:common])
end
# Protect against unaccounted-for, complex/slow queries.
# This is not a hard and fast rule, but is meant to encourage
# mindful inclusion of new queries.
def validate_indexes!
indexable_params = params.except(:ordered, :id, :project).keys
indexable_params << :project_id if params[:project]
indexable_params.sort!
raise ArgumentError, "An index should exist for params: #{indexable_params}" unless appropriate_index?(indexable_params)
end
def appropriate_index?(indexable_params)
return true if indexable_params.blank?
self.class.indexes.any? { |index| (index - indexable_params).empty? }
end
end
|
