Add tests to with_labels

This reproduces the error reported in issue #225, where `with_labels`
doesn't work at all the way it is intended, and in addition to that,
if you're using DirectFileStore, it can very easily corrupt your files.

The problem is the new metric received after calling `with_labels` is a
copy of the original, with the labels pre-set, but it has
**its own internal store**, so it doesn't actually impact the values of
the original metric, which is what gets exported by the registry.

Signed-off-by: Daniel Magliola <dmagliola@crystalgears.com>

Author: dmagliola

spec/prometheus/client/counter_spec.rb

@@ -3,6 +3,7 @@
 require 'prometheus/client'
 require 'prometheus/client/counter'
 require 'examples/metric_example'
+require 'prometheus/client/data_stores/direct_file_store'
 
 describe Prometheus::Client::Counter do
   # Reset the data store
@@ -45,12 +46,6 @@
           end.to change { counter.get(labels: { test: 'label' }) }.by(1.0)
         end.to_not change { counter.get(labels: { test: 'other' }) }
       end
-
-      it 'can pre-set labels using `with_labels`' do
-        expect { counter.increment }
-          .to raise_error(Prometheus::Client::LabelSetValidator::InvalidLabelSetError)
-        expect { counter.with_labels(test: 'label').increment }.not_to raise_error
-      end
     end
 
     it 'increments the counter by a given value' do
@@ -122,4 +117,57 @@
       end
     end
   end
+
+  describe '#with_labels' do
+    let(:expected_labels) { [:foo] }
+
+    it 'pre-sets labels for observations' do
+      expect { counter.increment }
+        .to raise_error(Prometheus::Client::LabelSetValidator::InvalidLabelSetError)
+      expect { counter.with_labels(foo: 'label').increment }.not_to raise_error
+    end
+
+    it 'registers `with_labels` observations in the original metric store' do
+      counter.increment(labels: { foo: 'value1'})
+      counter_with_labels = counter.with_labels({ foo: 'value2'})
+      counter_with_labels.increment(by: 2)
+
+      expect(counter_with_labels.values).to eql({foo: 'value1'} => 1.0, {foo: 'value2'} => 2.0)
+      expect(counter.values).to eql({foo: 'value1'} => 1.0, {foo: 'value2'} => 2.0)
+    end
+
+    context 'when using DirectFileStore' do
+      before do
+        Dir.glob('/tmp/prometheus_test/*').each { |file| File.delete(file) }
+        Prometheus::Client.config.data_store = Prometheus::Client::DataStores::DirectFileStore.new(dir: '/tmp/prometheus_test')
+      end
+
+      let(:expected_labels) { [:foo, :bar] }
+      
+      it "doesn't corrupt the data files" do
+        counter_with_labels = counter.with_labels({ foo: 'longervalue'})
+
+        # Initialize / read the files for both views of the metric
+        counter.increment(labels: { foo: 'value1', bar: 'zzz'})
+        counter_with_labels.increment(by: 2, labels: {bar: 'zzz'})
+
+        # After both MetricStores have their files, add a new entry to both
+        counter.increment(labels: { foo: 'value1', bar: 'aaa'})
+        counter_with_labels.increment(by: 2, labels: {bar: 'aaa'})
+
+        expect { counter.values }.not_to raise_error # Check it hasn't corrupted our files
+        expect { counter_with_labels.values }.not_to raise_error # Check it hasn't corrupted our files
+
+        expected_values = {
+          {foo: 'value1', bar: 'zzz'} => 1.0,
+          {foo: 'value1', bar: 'aaa'} => 1.0,
+          {foo: 'longervalue', bar: 'zzz'} => 2.0,
+          {foo: 'longervalue', bar: 'aaa'} => 2.0,
+        }
+
+        expect(counter.values).to eql(expected_values)
+        expect(counter_with_labels.values).to eql(expected_values)
+      end
+    end
+  end
 end

spec/prometheus/client/gauge_spec.rb

@@ -45,12 +45,6 @@
           end.to change { gauge.get(labels: { test: 'value' }) }.from(0).to(42)
         end.to_not change { gauge.get(labels: { test: 'other' }) }
       end
-
-      it 'can pre-set labels using `with_labels`' do
-        expect { gauge.set(10) }
-          .to raise_error(Prometheus::Client::LabelSetValidator::InvalidLabelSetError)
-        expect { gauge.with_labels(test: 'value').set(10) }.not_to raise_error
-      end
     end
 
     context 'given an invalid value' do
@@ -204,4 +198,23 @@
       end
     end
   end
+
+  describe '#with_labels' do
+    let(:expected_labels) { [:foo] }
+
+    it 'pre-sets labels for observations' do
+      expect { gauge.set(10) }
+        .to raise_error(Prometheus::Client::LabelSetValidator::InvalidLabelSetError)
+      expect { gauge.with_labels(foo: 'value').set(10) }.not_to raise_error
+    end
+
+    it 'registers `with_labels` observations in the original metric store' do
+      gauge.set(1, labels: { foo: 'value1'})
+      gauge_with_labels = gauge.with_labels({ foo: 'value2'})
+      gauge_with_labels.set(2)
+
+      expect(gauge_with_labels.values).to eql({foo: 'value1'} => 1.0, {foo: 'value2'} => 2.0)
+      expect(gauge.values).to eql({foo: 'value1'} => 1.0, {foo: 'value2'} => 2.0)
+    end
+  end
 end

spec/prometheus/client/histogram_spec.rb

@@ -80,12 +80,6 @@
           end.to change { histogram.get(labels: { test: 'value' }) }
         end.to_not change { histogram.get(labels: { test: 'other' }) }
       end
-
-      it 'can pre-set labels using `with_labels`' do
-        expect { histogram.observe(2) }
-          .to raise_error(Prometheus::Client::LabelSetValidator::InvalidLabelSetError)
-        expect { histogram.with_labels(test: 'value').observe(2) }.not_to raise_error
-      end
     end
 
     context "with non-string label values" do
@@ -189,4 +183,27 @@
       end
     end
   end
+
+  describe '#with_labels' do
+    let(:expected_labels) { [:foo] }
+
+    it 'pre-sets labels for observations' do
+      expect { histogram.observe(2) }
+        .to raise_error(Prometheus::Client::LabelSetValidator::InvalidLabelSetError)
+      expect { histogram.with_labels(foo: 'value').observe(2) }.not_to raise_error
+    end
+
+    it 'registers `with_labels` observations in the original metric store' do
+      histogram.observe(7, labels: { foo: 'value1'})
+      histogram_with_labels = histogram.with_labels({ foo: 'value2'})
+      histogram_with_labels.observe(20)
+
+      expected_values = {
+        {foo: 'value1'} => {'2.5' => 0.0, '5' => 0.0, '10' => 1.0, '+Inf' => 1.0, 'sum' => 7.0},
+        {foo: 'value2'} => {'2.5' => 0.0, '5' => 0.0, '10' => 0.0, '+Inf' => 1.0, 'sum' => 20.0}
+      }
+      expect(histogram_with_labels.values).to eql(expected_values)
+      expect(histogram.values).to eql(expected_values)
+    end
+  end
 end

spec/prometheus/client/summary_spec.rb

@@ -61,12 +61,6 @@
           end.to change { summary.get(labels: { test: 'value' })["count"] }
         end.to_not change { summary.get(labels: { test: 'other' })["count"] }
       end
-
-      it 'can pre-set labels using `with_labels`' do
-        expect { summary.observe(2) }
-          .to raise_error(Prometheus::Client::LabelSetValidator::InvalidLabelSetError)
-        expect { summary.with_labels(test: 'value').observe(2) }.not_to raise_error
-      end
     end
 
     context "with non-string label values" do
@@ -152,4 +146,27 @@
       end
     end
   end
+
+  describe '#with_labels' do
+    let(:expected_labels) { [:foo] }
+
+    it 'pre-sets labels for observations' do
+      expect { summary.observe(2) }
+        .to raise_error(Prometheus::Client::LabelSetValidator::InvalidLabelSetError)
+      expect { summary.with_labels(foo: 'value').observe(2) }.not_to raise_error
+    end
+
+    it 'registers `with_labels` observations in the original metric store' do
+      summary.observe(1, labels: { foo: 'value1'})
+      summary_with_labels = summary.with_labels({ foo: 'value2'})
+      summary_with_labels.observe(2)
+
+      expected_values = {
+        {foo: 'value1'} => { 'count' => 1.0, 'sum' => 1.0 },
+        {foo: 'value2'} => { 'count' => 1.0, 'sum' => 2.0 }
+      }
+      expect(summary_with_labels.values).to eql(expected_values)
+      expect(summary.values).to eql(expected_values)
+    end
+  end
 end