From a37354cb1834b876410a2b82b89c3308146d573c Mon Sep 17 00:00:00 2001
From: Natalia Goc <goc_natalia@ma-al.com>
Date: Wed, 25 Sep 2024 11:23:06 +0200
Subject: [PATCH] fix: message formatting errors in GELF exporter

The library used to transport GELF messages did not prefix extra fields
with `_` as was previously assumed and the application name was not
passed correctly from configuration to the exporter. Now fixed.

Related: goc_marek/salego#693
---
 pkg/exporters/gelf_exporter/gelf.go  | 9 ++++++++-
 pkg/exporters/gelf_exporter/trace.go | 1 +
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/pkg/exporters/gelf_exporter/gelf.go b/pkg/exporters/gelf_exporter/gelf.go
index a4e9151..d12cc5e 100644
--- a/pkg/exporters/gelf_exporter/gelf.go
+++ b/pkg/exporters/gelf_exporter/gelf.go
@@ -31,10 +31,17 @@ func Log(writer *gelf.UDPWriter, msg GELFMessage) {
 		if err != nil {
 			log.Println(err)
 		}
+	} else {
+		log.Fatalln("gelf.UDPWriter is not set!")
 	}
 }
 
 func (g GELFMessage) GELFFormat() *gelf.Message {
+	prefixedExtras := make(map[string]interface{}, len(g.ExtraFields))
+	for k, v := range g.ExtraFields {
+		prefixedExtras["_"+k] = v
+	}
+
 	return &gelf.Message{
 		Version:  "1.1",
 		Host:     g.Host,
@@ -42,6 +49,6 @@ func (g GELFMessage) GELFFormat() *gelf.Message {
 		Full:     g.LongMessage,
 		TimeUnix: float64(g.Timestamp.Unix()),
 		Level:    int32(g.Level),
-		Extra:    g.ExtraFields,
+		Extra:    prefixedExtras,
 	}
 }
diff --git a/pkg/exporters/gelf_exporter/trace.go b/pkg/exporters/gelf_exporter/trace.go
index 476187c..873655c 100644
--- a/pkg/exporters/gelf_exporter/trace.go
+++ b/pkg/exporters/gelf_exporter/trace.go
@@ -29,6 +29,7 @@ func New(options ...Option) (*Exporter, error) {
 
 	return &Exporter{
 		gelfWriter: writer,
+		appName:    cfg.AppName,
 	}, nil
 
 }