Fix step histogram label usage

The labels need to be passed to `#observe`

lib/gitlab/ci/pipeline/chain/command.rb

@@ -88,10 +88,8 @@ module Gitlab
           end
 
           def observe_step_duration(step_class, duration)
-            step = step_class.name.underscore.tr('/', '_')
-
-            metrics.pipeline_creation_step_duration_histogram(step)
-              .observe({}, duration.seconds)
+            metrics.pipeline_creation_step_duration_histogram
+              .observe({ step: step_class.name }, duration.seconds)
           end
 
           def observe_creation_duration(duration)

lib/gitlab/ci/pipeline/metrics.rb

@@ -4,6 +4,8 @@ module Gitlab
   module Ci
     module Pipeline
       class Metrics
+        extend Gitlab::Utils::StrongMemoize
+
         def self.pipeline_creation_duration_histogram
           name = :gitlab_ci_pipeline_creation_duration_seconds
           comment = 'Pipeline creation duration'
@@ -13,14 +15,16 @@ module Gitlab
           ::Gitlab::Metrics.histogram(name, comment, labels, buckets)
         end
 
-        def self.pipeline_creation_step_duration_histogram(step)
+        def self.pipeline_creation_step_duration_histogram
+          strong_memoize(:pipeline_creation_step_histogram) do
             name = :gitlab_ci_pipeline_creation_step_duration_seconds
             comment = 'Duration of each pipeline creation step'
-          labels = { step: step.remove('gitlab_ci_') }
+            labels = { step: nil }
             buckets = [0.01, 0.05, 0.1, 0.5, 1.0, 2.0, 5.0, 10.0, 15.0, 20.0, 50.0, 240.0]
 
             ::Gitlab::Metrics.histogram(name, comment, labels, buckets)
           end
+        end
 
         def self.pipeline_security_orchestration_policy_processing_duration_histogram
           name = :gitlab_ci_pipeline_security_orchestration_policy_processing_duration_seconds

spec/lib/gitlab/ci/pipeline/chain/command_spec.rb

@@ -347,10 +347,10 @@ RSpec.describe Gitlab::Ci::Pipeline::Chain::Command do
       histogram = double(:histogram)
       duration = 1.hour
 
-      expect(histogram).to receive(:observe).with({}, duration.seconds)
       expect(::Gitlab::Ci::Pipeline::Metrics).to receive(:pipeline_creation_step_duration_histogram)
-        .with('gitlab_ci_pipeline_chain_build')
         .and_return(histogram)
+      expect(histogram).to receive(:observe)
+        .with({ step: 'Gitlab::Ci::Pipeline::Chain::Build' }, duration.seconds)
 
       described_class.new.observe_step_duration(
         Gitlab::Ci::Pipeline::Chain::Build,

spec/lib/gitlab/ci/pipeline/chain/sequence_spec.rb

@@ -64,18 +64,12 @@ RSpec.describe Gitlab::Ci::Pipeline::Chain::Sequence do
     it 'adds step sequence duration to duration histogram' do
       expect(command.metrics)
         .to receive(:pipeline_creation_step_duration_histogram)
-        .with('first_step')
-        .ordered
-        .and_return(histogram)
-      expect(command.metrics)
-        .to receive(:pipeline_creation_step_duration_histogram)
-        .with('second_step')
-        .ordered
+        .twice
         .and_return(histogram)
+      expect(histogram).to receive(:observe).with({ step: 'FirstStep' }, any_args).ordered
+      expect(histogram).to receive(:observe).with({ step: 'SecondStep' }, any_args).ordered
 
       subject.build!
-
-      expect(histogram).to have_received(:observe).twice
     end
 
     it 'records pipeline size by pipeline source in a histogram' do

spec/lib/gitlab/ci/pipeline/metrics_spec.rb

@@ -5,17 +5,17 @@ require 'spec_helper'
 RSpec.describe ::Gitlab::Ci::Pipeline::Metrics do
   describe '.pipeline_creation_step_duration_histogram' do
     it 'adds the step to the step duration histogram' do
-      step = 'gitlab_ci_pipeline_chain_build'
+      described_class.clear_memoization(:pipeline_creation_step_histogram)
 
       expect(::Gitlab::Metrics).to receive(:histogram)
         .with(
           :gitlab_ci_pipeline_creation_step_duration_seconds,
           'Duration of each pipeline creation step',
-          { step: 'pipeline_chain_build' },
+          { step: nil },
           [0.01, 0.05, 0.1, 0.5, 1.0, 2.0, 5.0, 10.0, 15.0, 20.0, 50.0, 240.0]
         )
 
-      described_class.pipeline_creation_step_duration_histogram(step)
+      described_class.pipeline_creation_step_duration_histogram
     end
   end
 end