graphql: data dog instrumentation

closes RECNVS-325

Test plan:
  * do something to monitor statsd traffic (maybe
    `nc -kul 8125`?)
  * queries written in graphiql should not be instrumented
  * student context card queries should be logged

Change-Id: Ie86075b739df36e49b5f9ebcf320e50f8c140ecc
Reviewed-on: https://gerrit.instructure.com/141965
Tested-by: Jenkins
Reviewed-by: Jonathan Featherstone <jfeatherstone@instructure.com>
QA-Review: Collin Parrish <cparrish@instructure.com>
Product-Review: Cameron Matheson <cameron@instructure.com>

Gemfile.d/app.rb

@@ -163,3 +163,4 @@ gem 'twitter', path: 'gems/twitter'
 gem 'vericite_api', '1.5.3'
 gem 'utf8_cleaner', path: 'gems/utf8_cleaner'
 gem 'workflow', path: 'gems/workflow'
+gem 'dogstatsd-ruby', '3.3.0'

app/controllers/graphql_controller.rb

@@ -4,22 +4,32 @@ class GraphQLController < ApplicationController
   before_action :require_user, except: :execute
   before_action :require_graphql_feature_flag
 
+
   def execute
     query = params[:query]
     variables = params[:variables] || {}
+    tracers = if request.headers["GraphQL-Metrics"] == "true"
+                domain = request.host_with_port.sub(':', '_')
+                [Tracers::DatadogTracer.new(domain)]
+              else
+                []
+              end
     context = {
       current_user: @current_user,
       session: session,
       request: request,
+      tracers: tracers
     }
+    result = nil
 
     ActiveRecord::Base.transaction do
       timeout = Integer(Setting.get('graphql_statement_timeout', '60_000'))
       ActiveRecord::Base.connection.execute "SET statement_timeout = #{timeout}"
 
       result = CanvasSchema.execute(query, variables: variables, context: context)
-      render json: result
     end
+
+    render json: result
   end
 
   def graphiql

app/graphql/tracers/datadog_tracer.rb

@@ -0,0 +1,28 @@
+require 'datadog/statsd'
+
+module Tracers
+  class DatadogTracer
+    def initialize(domain)
+      @domain = domain
+      @statsd = Datadog::Statsd.new('localhost', 8125)
+    end
+
+    def trace(key, metadata)
+      if key == "execute_query"
+        @statsd.batch do |statsd|
+          query_name = metadata[:query].operation_name || "unnamed"
+          tags = [
+            "query_md5:#{Digest::MD5.hexdigest(metadata[:query].query_string)}",
+            "domain:#@domain",
+          ]
+          statsd.increment("graphql.#{query_name}.count", tags: tags)
+          statsd.time("graphql.#{query_name}.time", tags: tags) do
+            yield
+          end
+        end
+      else
+        yield
+      end
+    end
+  end
+end

app/jsx/context_cards/GraphQLStudentContextTray.js

@@ -10,6 +10,7 @@ const client = new ApolloClient({
     opts: {
       headers: {
         'X-Requested-With': 'XMLHttpRequest',
+        'GraphQL-Metrics': true,
         'X-CSRF-Token': $.cookie('_csrf_token') // TODO: probably need to move this io a middleware (http://dev.apollodata.com/core/network.html)
       },
       credentials: 'same-origin'

spec/controllers/graphql_controller_spec.rb

@@ -62,5 +62,18 @@ describe GraphQLController do
       post :execute, params: {query: "{}"}
       expect(JSON.parse(response.body)["errors"]).not_to be_blank
     end
+
+    context "data dog metrics" do
+      it "reports data dog metrics if requested" do
+        expect_any_instance_of(Tracers::DatadogTracer).to receive :trace
+        request.headers["GraphQL-Metrics"] = "true"
+        post :execute, params: {query: '{legacyNode(User, 1) { id }'}
+      end
+
+      it "doesn't report normally" do
+        expect_any_instance_of(Tracers::DatadogTracer).not_to receive :trace
+        post :execute, params: {query: '{legacyNode(User, 1) { id }'}
+      end
+    end
   end
 end