From 03b8a00743115b2236a45a3f359ef0c86c9c2f6f Mon Sep 17 00:00:00 2001
From: Marco Pfatschbacher <marco@graylog.com>
Date: Fri, 13 Oct 2023 12:43:12 +0100
Subject: [PATCH] Abort request on missing Graylog server version

If we fail to read the server version from Graylog,
stop using a fallback to 4.0.0 and retry the request
instead.

In scenarios with multiple Graylog nodes behind a load balancer,
this can lead to the sidecar temporarly stopping all collectors.

Fixes #481
---
 api/graylog.go          | 8 +++-----
 services/periodicals.go | 5 ++++-
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/api/graylog.go b/api/graylog.go
index bb78baa..d3f7886 100644
--- a/api/graylog.go
+++ b/api/graylog.go
@@ -42,22 +42,20 @@ var (
 )
 
 func GetServerVersion(httpClient *http.Client, ctx *context.Ctx) (*GraylogVersion, error) {
-	// In case of an error just assume 4.0.0
-	fallbackVersion, _ := NewGraylogVersion("4.0.0")
-
 	c := rest.NewClient(httpClient, ctx)
 	c.BaseURL = ctx.ServerUrl
 	r, err := c.NewRequest("GET", "/", nil, nil)
 	if err != nil {
 		log.Errorf("Cannot retrieve server version %v", err)
-		return fallbackVersion, err
+		return nil, err
 	}
 	versionResponse := graylog.ServerVersionResponse{}
 	resp, err := c.Do(r, &versionResponse)
 	if err != nil || resp == nil {
 		log.Errorf("Error fetching server version %v", err)
-		return fallbackVersion, err
+		return nil, err
 	}
+	log.Debugf("Graylog server version %v", versionResponse.Version)
 	return NewGraylogVersion(versionResponse.Version)
 }
 
diff --git a/services/periodicals.go b/services/periodicals.go
index a630cf6..8efa7fb 100644
--- a/services/periodicals.go
+++ b/services/periodicals.go
@@ -49,7 +49,10 @@ func StartPeriodicals(context *context.Ctx) {
 			}
 			firstRun = false
 
-			serverVersion, _ := api.GetServerVersion(httpClient, context)
+			serverVersion, err := api.GetServerVersion(httpClient, context)
+			if err != nil {
+				continue
+			}
 
 			// registration regResponse contains configuration assignments
 			regResponse, err := updateCollectorRegistration(httpClient, lastRegResponse.Checksum, context, serverVersion)