Merge branch '58839-automatically-set-prometheus-step-interval' into 'master'

Resolve "Automatically set Prometheus step interval"

Closes #58839

See merge request gitlab-org/gitlab-ce!26441

2 files changed, 35 insertions, 3 deletions

diff --git a/spec/lib/gitlab/prometheus_client_spec.rb b/spec/lib/gitlab/prometheus_client_spec.rb
index 4c3b8deefb9..2517ee71f24 100644
--- a/spec/lib/gitlab/prometheus_client_spec.rb
+++ b/spec/lib/gitlab/prometheus_client_spec.rb
@@ -230,4 +230,32 @@ describe Gitlab::PrometheusClient do
       let(:execute_query) { subject.query_range(prometheus_query) }
     end
   end
+
+  describe '.compute_step' do
+    using RSpec::Parameterized::TableSyntax
+
+    let(:now) { Time.now.utc }
+
+    subject { described_class.compute_step(start, stop) }
+
+    where(:time_interval_in_seconds, :step) do
+      0               | 60
+      10.hours        | 60
+      10.hours + 1    | 61
+      # frontend options
+      30.minutes      | 60
+      3.hours         | 60
+      8.hours         | 60
+      1.day           | 144
+      3.days          | 432
+      1.week          | 1008
+    end
+
+    with_them do
+      let(:start) { now - time_interval_in_seconds }
+      let(:stop) { now }
+
+      it { is_expected.to eq(step) }
+    end
+  end
 end
diff --git a/spec/support/helpers/prometheus_helpers.rb b/spec/support/helpers/prometheus_helpers.rb
index ce1f9fce10d..08d1d7a6059 100644
--- a/spec/support/helpers/prometheus_helpers.rb
+++ b/spec/support/helpers/prometheus_helpers.rb
@@ -25,12 +25,16 @@ module PrometheusHelpers
     "https://prometheus.example.com/api/v1/query?#{query}"
   end
 
-  def prometheus_query_range_url(prometheus_query, start: 8.hours.ago, stop: Time.now.to_f)
+  def prometheus_query_range_url(prometheus_query, start: 8.hours.ago, stop: Time.now, step: nil)
+    start = start.to_f
+    stop = stop.to_f
+    step ||= Gitlab::PrometheusClient.compute_step(start, stop)
+
     query = {
       query: prometheus_query,
-      start: start.to_f,
+      start: start,
       end: stop,
-      step: 1.minute.to_i
+      step: step
     }.to_query
 
     "https://prometheus.example.com/api/v1/query_range?#{query}"