Connect via Kubernetes to Prometheus running in Kubernetes clusterconnect-to-prometheus-via-kubernetes

4 files changed, 43 insertions, 22 deletions

diff --git a/app/controllers/concerns/service_params.rb b/app/controllers/concerns/service_params.rb
index be2e6c7f193..ef6fde197f0 100644
--- a/app/controllers/concerns/service_params.rb
+++ b/app/controllers/concerns/service_params.rb
@@ -59,7 +59,8 @@ module ServiceParams
     :url,
     :user_key,
     :username,
-    :webhook
+    :webhook,
+    :use_kubernetes
   ].freeze
 
   # Parameters to ignore if no value is specified
diff --git a/app/models/project_services/kubernetes_service.rb b/app/models/project_services/kubernetes_service.rb
index b2494a0be6e..67c73f63e95 100644
--- a/app/models/project_services/kubernetes_service.rb
+++ b/app/models/project_services/kubernetes_service.rb
@@ -134,6 +134,14 @@ class KubernetesService < DeploymentService
     { pods: pods }
   end
 
+  def rest_client_for(kind, name, port, namespace = '')
+    kube_client = build_kubeclient!
+    rest_client = kube_client.rest_client
+    base_url = rest_client.url
+    proxy_url = kube_client.proxy_url(kind, name, port, namespace)
+    [rest_client[proxy_url.sub(base_url, '')], kube_client.headers]
+  end
+
   TEMPLATE_PLACEHOLDER = 'Kubernetes namespace'.freeze
 
   private
diff --git a/app/models/project_services/prometheus_service.rb b/app/models/project_services/prometheus_service.rb
index ec72cb6856d..74d9e36542b 100644
--- a/app/models/project_services/prometheus_service.rb
+++ b/app/models/project_services/prometheus_service.rb
@@ -7,9 +7,10 @@ class PrometheusService < MonitoringService
 
   #  Access to prometheus is directly through the API
   prop_accessor :api_url
+  boolean_accessor :use_kubernetes
 
   with_options presence: true, if: :activated? do
-    validates :api_url, url: true
+    validates :api_url, url: true, unless: :use_kubernetes?
   end
 
   after_save :clear_reactive_cache!
@@ -46,6 +47,11 @@ class PrometheusService < MonitoringService
   def fields
     [
       {
+        type: 'checkbox',
+        name: 'use_kubernetes',
+        title: 'Use Kubernetes Service'
+      },
+      {
         type: 'text',
         name: 'api_url',
         title: 'API URL',
@@ -88,6 +94,14 @@ class PrometheusService < MonitoringService
   end
 
   def client
-    @prometheus ||= Gitlab::PrometheusClient.new(api_url: api_url)
+    rest_client, headers = kubernetes_prometheus
+
+    @prometheus ||= Gitlab::PrometheusClient.new(api_url: api_url, rest_client: rest_client, headers: headers)
+  end
+
+  def kubernetes_prometheus
+    return unless use_kubernetes?
+
+    project.kubernetes_service&.rest_client_for('service', 'prometheus', 9090, 'prometheus')
   end
 end
diff --git a/lib/gitlab/prometheus_client.rb b/lib/gitlab/prometheus_client.rb
index 5b51a1779dd..22f744373ce 100644
--- a/lib/gitlab/prometheus_client.rb
+++ b/lib/gitlab/prometheus_client.rb
@@ -3,10 +3,12 @@ module Gitlab
 
   # Helper methods to interact with Prometheus network services & resources
   class PrometheusClient
-    attr_reader :api_url
+    attr_reader :api_url, :rest_client, :headers
 
-    def initialize(api_url:)
+    def initialize(api_url:, rest_client: nil, headers: nil)
       @api_url = api_url
+      @rest_client = rest_client || RestClient::Resource.new(api_url)
+      @headers = headers || {}
     end
 
     def ping
@@ -32,24 +34,15 @@ module Gitlab
     private
 
     def json_api_get(type, args = {})
-      get(join_api_url(type, args))
+      path = ['api', 'v1', type].join('/')
+      get(path, 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))
+    def get(path, args)
+      response = rest_client[path].get(headers.merge(params: args))
+      handle_response(response)
     rescue SocketError
       raise PrometheusError, "Can't connect to #{url}"
     rescue OpenSSL::SSL::SSLError
@@ -59,15 +52,20 @@ module Gitlab
     end
 
     def handle_response(response)
-      if response.code == 200 && response['status'] == 'success'
-        response['data'] || {}
+      json_data = json_response(response)
+      if response.code == 200 && json_data['status'] == 'success'
+        json_data['data'] || {}
       elsif response.code == 400
-        raise PrometheusError, response['error'] || 'Bad data received'
+        raise PrometheusError, json_data['error'] || 'Bad data received'
       else
         raise PrometheusError, "#{response.code} - #{response.body}"
       end
     end
 
+    def json_response(response)
+      JSON.parse(response.body)
+    end
+
     def get_result(expected_type)
       data = yield
       data['result'] if data['resultType'] == expected_type