Merge branch 'zj-mattermost-slash-config' of gitlab.com:gitlab-org/gitlab-ce...

Merge branch 'zj-mattermost-slash-config' of gitlab.com:gitlab-org/gitlab-ce into zj-mattermost-slash-config

lib/mattermost/error.rb

+module Mattermost
+  class Error < StandardError; end
+end

lib/mattermost/session.rb

@@ -26,6 +26,8 @@ module Mattermost
     include Doorkeeper::Helpers::Controller
     include HTTParty
 
+    LEASE_TIMEOUT = 60
+
     base_uri Settings.mattermost.host
 
     attr_accessor :current_resource_owner, :token
@@ -35,6 +37,7 @@ module Mattermost
     end
 
     def with_session
+      with_lease do
         raise NoSessionError unless create
 
         begin
@@ -45,6 +48,7 @@ module Mattermost
           destroy
         end
       end
+    end
 
     # Next methods are needed for Doorkeeper
     def pre_auth
@@ -130,5 +134,25 @@ module Mattermost
         response.headers['token']
       end
     end
+
+    def with_lease
+      lease_uuid = lease_try_obtain
+      raise NoSessionError unless lease_uuid
+
+      begin
+        yield
+      ensure
+        Gitlab::ExclusiveLease.cancel(lease_key, lease_uuid)
+      end
+    end
+
+    def lease_key
+      "mattermost:session"
+    end
+
+    def lease_try_obtain
+      lease = ::Gitlab::ExclusiveLease.new(lease_key, timeout: LEASE_TIMEOUT)
+      lease.try_obtain
+    end
   end
 end