1 files changed, 63 insertions, 20 deletions

diff --git a/lib/gitlab/prometheus_client.rb b/lib/gitlab/prometheus_client.rb
index 45828c77a33..f13156f898e 100644
--- a/lib/gitlab/prometheus_client.rb
+++ b/lib/gitlab/prometheus_client.rb
@@ -6,6 +6,14 @@ module Gitlab
     Error = Class.new(StandardError)
     QueryError = Class.new(Gitlab::PrometheusClient::Error)
 
+    # Target number of data points for `query_range`.
+    # Please don't exceed the limit of 11000 data points
+    # See https://github.com/prometheus/prometheus/blob/91306bdf24f5395e2601773316945a478b4b263d/web/api/v1/api.go#L347
+    QUERY_RANGE_DATA_POINTS = 600
+
+    # Minimal value of the `step` parameter for `query_range` in seconds.
+    QUERY_RANGE_MIN_STEP = 60
+
     attr_reader :rest_client, :headers
 
     def initialize(rest_client)
@@ -16,6 +24,19 @@ module Gitlab
       json_api_get('query', query: '1')
     end
 
+    def proxy(type, args)
+      path = api_path(type)
+      get(path, args)
+    rescue RestClient::ExceptionWithResponse => ex
+      if ex.response
+        ex.response
+      else
+        raise PrometheusClient::Error, "Network connection error"
+      end
+    rescue RestClient::Exception
+      raise PrometheusClient::Error, "Network connection error"
+    end
+
     def query(query, time: Time.now)
       get_result('vector') do
         json_api_get('query', query: query, time: time.to_f)
@@ -23,12 +44,18 @@ module Gitlab
     end
 
     def query_range(query, start: 8.hours.ago, stop: Time.now)
+      start = start.to_f
+      stop = stop.to_f
+      step = self.class.compute_step(start, stop)
+
       get_result('matrix') do
-        json_api_get('query_range',
-                     query: query,
-                     start: start.to_f,
-                     end: stop.to_f,
-                     step: 1.minute.to_i)
+        json_api_get(
+          'query_range',
+          query: query,
+          start: start,
+          end: stop,
+          step: step
+        )
       end
     end
 
@@ -40,24 +67,24 @@ module Gitlab
       json_api_get('series', 'match': matches, start: start.to_f, end: stop.to_f)
     end
 
+    def self.compute_step(start, stop)
+      diff = stop - start
+
+      step = (diff / QUERY_RANGE_DATA_POINTS).ceil
+
+      [QUERY_RANGE_MIN_STEP, step].max
+    end
+
     private
 
-    def json_api_get(type, args = {})
-      path = ['api', 'v1', type].join('/')
-      get(path, args)
-    rescue JSON::ParserError
-      raise PrometheusClient::Error, 'Parsing response failed'
-    rescue Errno::ECONNREFUSED
-      raise PrometheusClient::Error, 'Connection refused'
+    def api_path(type)
+      ['api', 'v1', type].join('/')
     end
 
-    def get(path, args)
-      response = rest_client[path].get(params: args)
+    def json_api_get(type, args = {})
+      path = api_path(type)
+      response = get(path, args)
       handle_response(response)
-    rescue SocketError
-      raise PrometheusClient::Error, "Can't connect to #{rest_client.url}"
-    rescue OpenSSL::SSL::SSLError
-      raise PrometheusClient::Error, "#{rest_client.url} contains invalid SSL data"
     rescue RestClient::ExceptionWithResponse => ex
       if ex.response
         handle_exception_response(ex.response)
@@ -68,8 +95,18 @@ module Gitlab
       raise PrometheusClient::Error, "Network connection error"
     end
 
+    def get(path, args)
+      rest_client[path].get(params: args)
+    rescue SocketError
+      raise PrometheusClient::Error, "Can't connect to #{rest_client.url}"
+    rescue OpenSSL::SSL::SSLError
+      raise PrometheusClient::Error, "#{rest_client.url} contains invalid SSL data"
+    rescue Errno::ECONNREFUSED
+      raise PrometheusClient::Error, 'Connection refused'
+    end
+
     def handle_response(response)
-      json_data = JSON.parse(response.body)
+      json_data = parse_json(response.body)
       if response.code == 200 && json_data['status'] == 'success'
         json_data['data'] || {}
       else
@@ -81,7 +118,7 @@ module Gitlab
       if response.code == 200 && response['status'] == 'success'
         response['data'] || {}
       elsif response.code == 400
-        json_data = JSON.parse(response.body)
+        json_data = parse_json(response.body)
         raise PrometheusClient::QueryError, json_data['error'] || 'Bad data received'
       else
         raise PrometheusClient::Error, "#{response.code} - #{response.body}"
@@ -92,5 +129,11 @@ module Gitlab
       data = yield
       data['result'] if data['resultType'] == expected_type
     end
+
+    def parse_json(response_body)
+      JSON.parse(response_body)
+    rescue JSON::ParserError
+      raise PrometheusClient::Error, 'Parsing response failed'
+    end
   end
 end