add comments for redis metrics

services/document-updater/app/coffee/RedisManager.coffee

@@ -41,6 +41,7 @@ module.exports = RedisManager =
 			logger.error {err: error, doc_id: doc_id, docLines: docLines}, error.message
 			return callback(error)
 		docHash = RedisManager._computeHash(docLines)
+		# record bytes sent to redis
 		metrics.summary "redis.docLines", docLines.length, {status: "set"}
 		logger.log {project_id, doc_id, version, docHash, pathname, projectHistoryId}, "putting doc in redis"
 		RedisManager._serializeRanges ranges, (error, ranges) ->
@@ -90,6 +91,7 @@ module.exports = RedisManager =
 			return callback(error) if error?
 			length = response?[0]
 			if length > 0
+				# record bytes freed in redis
 				metrics.summary "redis.docLines", length, {status: "del"}
 			multi = rclient.multi()
 			multi.srem keys.docsInProject(project_id:project_id), doc_id