Class: Prometheus::Client::DataStores::DirectFileStore

Inherits:
Object
  • Object
show all
Defined in:
lib/prometheus/client/data_stores/direct_file_store.rb

Overview

Stores data in binary files, one file per process and per metric. This is generally the recommended store to use to deal with pre-fork servers and other “multi-process” scenarios.

Each process will get a file for a metric, and it will manage its contents by storing keys next to binary-encoded Floats, and keeping track of the offsets of those Floats, to be able to update them directly as they increase.

When exporting metrics, the process that gets scraped by Prometheus will find all the files that apply to a metric, read their contents, and aggregate them (generally that means SUMming the values for each labelset).

In order to do this, each Metric needs an :aggregation setting, specifying how to aggregate the multiple possible values we can get for each labelset. By default, they are ‘SUM`med, which is what most use cases call for (counters and histograms, for example). However, for Gauges, it’s possible to set MAX or MIN as aggregation, to get the highest value of all the processes / threads.

Defined Under Namespace

Classes: FileMappedDict, InvalidStoreSettingsError

Constant Summary collapse

AGGREGATION_MODES = 
[MAX = :max, MIN = :min, SUM = :sum, ALL = :all]
DEFAULT_METRIC_SETTINGS = 
{ aggregation: SUM }
DEFAULT_GAUGE_SETTINGS = 
{ aggregation: ALL }

Instance Method Summary collapse

Constructor Details

#initialize(dir:) ⇒ DirectFileStore

Returns a new instance of DirectFileStore.



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# File 'lib/prometheus/client/data_stores/direct_file_store.rb', line 32

def initialize(dir:)
  @store_settings = { dir: dir }
  FileUtils.mkdir_p(dir)
end

Instance Method Details

#for_metric(metric_name, metric_type:, metric_settings: {}) ⇒ Object 



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# File 'lib/prometheus/client/data_stores/direct_file_store.rb', line 37

def for_metric(metric_name, metric_type:, metric_settings: {})
  default_settings = DEFAULT_METRIC_SETTINGS
  if metric_type == :gauge
    default_settings = DEFAULT_GAUGE_SETTINGS
  end

  settings = default_settings.merge(metric_settings)
  validate_metric_settings(settings)

  MetricStore.new(metric_name: metric_name,
                  store_settings: @store_settings,
                  metric_settings: settings)
end