Use service settings instead of config file settings to present issues.

app/helpers/issues_helper.rb

@@ -16,7 +16,7 @@ module IssuesHelper
   def url_for_project_issues(project = @project)
     return '' if project.nil?
 
-    if project.used_default_issues_tracker? || !external_issues_tracker_enabled?
+    if project.used_default_issues_tracker? || !project.external_issues_tracker_enabled?
       project_issues_path(project)
     else
       url = Gitlab.config.issues_tracker[project.issues_tracker]['project_url']
@@ -28,7 +28,7 @@ module IssuesHelper
   def url_for_new_issue(project = @project)
     return '' if project.nil?
 
-    if project.used_default_issues_tracker? || !external_issues_tracker_enabled?
+    if project.used_default_issues_tracker? || !project.external_issues_tracker_enabled?
       url = new_project_issue_path project_id: project
     else
       issues_tracker = Gitlab.config.issues_tracker[project.issues_tracker]
@@ -41,7 +41,7 @@ module IssuesHelper
   def url_for_issue(issue_iid, project = @project)
     return '' if project.nil?
 
-    if project.used_default_issues_tracker? || !external_issues_tracker_enabled?
+    if project.used_default_issues_tracker? || !project.external_issues_tracker_enabled?
       url = project_issue_url project_id: project, id: issue_iid
     else
       url = Gitlab.config.issues_tracker[project.issues_tracker]['issues_url']
@@ -77,11 +77,6 @@ module IssuesHelper
     ts.html_safe
   end
 
-  # Checks if issues_tracker setting exists in gitlab.yml
-  def external_issues_tracker_enabled?
-    Gitlab.config.issues_tracker && Gitlab.config.issues_tracker.values.any?
-  end
-
   def bulk_update_milestone_options
     options_for_select(['None (backlog)']) +
         options_from_collection_for_select(project_active_milestones, 'id',

app/models/project.rb

@@ -309,6 +309,18 @@ class Project < ActiveRecord::Base
     self.issues_tracker == Project.issues_tracker.default_value
   end
 
+  def external_issues_tracker_enabled?
+    external_issues_trackers.any?
+  end
+
+  def external_issues_trackers
+    services.select { |service| service.category == :issue_tracker }
+  end
+
+  def external_issue_tracker
+    @external_issues_tracker ||= external_issues_trackers.select(&:activated?).first
+  end
+
   def can_have_issues_tracker_id?
     self.issues_enabled && !self.used_default_issues_tracker?
   end

app/models/project_services/issue_tracker_service.rb

 class IssueTrackerService < Service
 
+  def category
+    :issue_tracker
+  end
+
   def project_url
     # implement inside child
   end

app/models/project_services/redmine_service.rb

@@ -48,9 +48,9 @@ class RedmineService < IssueTrackerService
   end
 
   def set_project_url
-    id = self.project.issue_tracker_id
+    id = self.project.issues_tracker_id
     if id
-      issues_tracker['project_url'].gsub(":issue_tracker_id", id)
+      issues_tracker['project_url'].gsub(":issues_tracker_id", id)
     else
       issues_tracker['project_url']
     end

lib/gitlab/markdown.rb

@@ -208,7 +208,7 @@ module Gitlab
     end
 
     def reference_issue(identifier, project = @project, prefix_text = nil)
-      if project.used_default_issues_tracker? || !external_issues_tracker_enabled?
+      if project.used_default_issues_tracker? || !project.external_issues_tracker_enabled?
         if project.issue_exists? identifier
           url = url_for_issue(identifier, project)
           title = title_for_issue(identifier, project)
@@ -220,8 +220,7 @@ module Gitlab
           link_to("#{prefix_text}##{identifier}", url, options)
         end
       else
-        config = Gitlab.config
-        external_issue_tracker = config.issues_tracker[project.issues_tracker]
+        external_issue_tracker = project.external_issue_tracker
         if external_issue_tracker.present?
           reference_external_issue(identifier, external_issue_tracker, project,
                                    prefix_text)
@@ -270,7 +269,7 @@ module Gitlab
     def reference_external_issue(identifier, issue_tracker, project = @project,
                                  prefix_text = nil)
       url = url_for_issue(identifier, project)
-      title = issue_tracker['title']
+      title = issue_tracker.title
 
       options = html_options.merge(
         title: "Issue in #{title}",