1 files changed, 70 insertions, 0 deletions
diff --git a/lib/gitlab/prometheus.rb b/lib/gitlab/prometheus.rb
new file mode 100644
index 00000000000..62239779454
--- /dev/null
+++ b/lib/gitlab/prometheus.rb
@@ -0,0 +1,70 @@
+module Gitlab
+  PrometheusError = Class.new(StandardError)
+
+  # Helper methods to interact with Prometheus network services & resources
+  class Prometheus
+    attr_reader :api_url
+
+    def initialize(api_url:)
+      @api_url = api_url
+    end
+
+    def ping
+      json_api_get('query', query: '1')
+    end
+
+    def query(query)
+      get_result('vector') do
+        json_api_get('query', query: query)
+      end
+    end
+
+    def query_range(query, start: 8.hours.ago)
+      get_result('matrix') do
+        json_api_get('query_range',
+          query: query,
+          start: start.to_f,
+          end: Time.now.utc.to_f,
+          step: 1.minute.to_i)
+      end
+    end
+
+    private
+
+    def json_api_get(type, args = {})
+      get(join_api_url(type, args))
+    rescue Errno::ECONNREFUSED
+      raise PrometheusError, 'Connection refused'
+    end
+
+    def join_api_url(type, args = {})
+      url = URI.parse(api_url)
+    rescue URI::Error
+      raise PrometheusError, "Invalid API URL: #{api_url}"
+    else
+      url.path = [url.path.sub(%r{/+\z}, ''), 'api', 'v1', type].join('/')
+      url.query = args.to_query
+
+      url.to_s
+    end
+
+    def get(url)
+      handle_response(HTTParty.get(url))
+    end
+
+    def handle_response(response)
+      if response.code == 200 && response['status'] == 'success'
+        response['data'] || {}
+      elsif response.code == 400
+        raise PrometheusError, response['error'] || 'Bad data received'
+      else
+        raise PrometheusError, "#{response.code} - #{response.body}"
+      end
+    end
+
+    def get_result(expected_type)
+      data = yield
+      data['result'] if data['resultType'] == expected_type
+    end
+  end
+end