Add :clean_dir option and clean_pid method to DirectFileStore

lib/prometheus/client/data_stores/direct_file_store.rb

@@ -1,6 +1,8 @@
 require 'fileutils'
 require "cgi"
 
+require 'prometheus/client/version'
+
 module Prometheus
   module Client
     module DataStores
@@ -33,9 +35,15 @@ class InvalidStoreSettingsError < StandardError; end
         DEFAULT_METRIC_SETTINGS = { aggregation: SUM }
         DEFAULT_GAUGE_SETTINGS = { aggregation: ALL }
 
-        def initialize(dir:)
+        def initialize(dir:, clean_dir: false)
           @store_settings = { dir: dir }
           FileUtils.mkdir_p(dir)
+
+          if clean_dir
+            Dir.glob(File.join(dir, "#{ MetricStore::FILENAME_PREFIX }_*___*.bin")).each do |file_path|
+              File.unlink(file_path)
+            end
+          end
         end
 
         def for_metric(metric_name, metric_type:, metric_settings: {})
@@ -52,6 +60,12 @@ def for_metric(metric_name, metric_type:, metric_settings: {})
                           metric_settings: settings)
         end
 
+        def clean_pid(pid)
+          Dir.glob(File.join(@store_settings[:dir], "#{ MetricStore::FILENAME_PREFIX }_*___#{pid}.bin")).each do |file_path|
+            File.unlink(file_path)
+          end
+        end
+
         private
 
         def validate_metric_settings(metric_settings)
@@ -68,6 +82,7 @@ def validate_metric_settings(metric_settings)
         end
 
         class MetricStore
+          FILENAME_PREFIX = "prometheus_#{ Prometheus::Client::VERSION }"
           attr_reader :metric_name, :store_settings
 
           def initialize(metric_name:, store_settings:, metric_settings:)
@@ -168,12 +183,12 @@ def internal_store
 
           # Filename for this metric's PStore (one per process)
           def filemap_filename
-            filename = "metric_#{ metric_name }___#{ process_id }.bin"
+            filename = "#{ FILENAME_PREFIX }_#{ metric_name }___#{ process_id }.bin"
             File.join(@store_settings[:dir], filename)
           end
 
           def stores_for_metric
-            Dir.glob(File.join(@store_settings[:dir], "metric_#{ metric_name }___*"))
+            Dir.glob(File.join(@store_settings[:dir], "#{ FILENAME_PREFIX }_#{ metric_name }___*.bin"))
           end
 
           def process_id

spec/prometheus/client/data_stores/direct_file_store_spec.rb

@@ -4,14 +4,9 @@
 require 'examples/data_store_example'
 
 describe Prometheus::Client::DataStores::DirectFileStore do
-  subject { described_class.new(dir: "/tmp/prometheus_test") }
+  subject { described_class.new(dir: "/tmp/prometheus_test", clean_dir: true) }
   let(:metric_store) { subject.for_metric(:metric_name, metric_type: :counter) }
 
-  # Reset the PStores
-  before do
-    Dir.glob('/tmp/prometheus_test/*').each { |file| File.delete(file) }
-  end
-
   it_behaves_like Prometheus::Client::DataStores
 
   it "only accepts valid :aggregation as Metric Settings" do
@@ -57,6 +52,15 @@
     ms2.increment(labels: {}, by: 1)
   end
 
+  it "can clean files from old processes" do
+    allow(Process).to receive(:pid).and_return(12345)
+    ms = metric_store
+    ms.increment(labels: {}, by: 1)
+    expect(ms.all_values).to eq({} => 1.0)
+    subject.clean_pid(12345)
+    expect(ms.all_values).to be_empty
+  end
+
   context "when process is forked" do
     it "opens a new internal store to avoid two processes using the same file" do
       allow(Process).to receive(:pid).and_return(12345)