From 4e2773a8fa2fcc74c714fb7af9bb3126afbacf14 Mon Sep 17 00:00:00 2001
From: Yen-Cheng Chou <3055688+StevenYCChou@users.noreply.github.com>
Date: Thu, 3 Oct 2019 13:42:03 -0400
Subject: [PATCH] Document error handling for grpc codes. (#183)

Document why making grpc codes DeadlineExceeded and Unavailable
as recoverable errors.
---
 stackdriver/client.go | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/stackdriver/client.go b/stackdriver/client.go
index 8a9a9e02..7904f30f 100644
--- a/stackdriver/client.go
+++ b/stackdriver/client.go
@@ -180,6 +180,16 @@ func (c *Client) Store(req *monitoring.CreateTimeSeriesRequest) error {
 					return
 				}
 				switch status.Code() {
+				// codes.DeadlineExceeded:
+				//   It is safe to retry
+				//   google.monitoring.v3.MetricService.CreateTimeSeries
+				//   requests with backoff because QueueManager
+				//   enforces in-order writes on a time series, which
+				//   is a requirement for Stackdriver monitoring.
+				//
+				// codes.Unavailable:
+				//   The condition is most likely transient. The request can
+				//   be retried with backoff.
 				case codes.DeadlineExceeded, codes.Unavailable:
 					errors <- recoverableError{err}
 				default: