From 891381c371a988696f9cbc75316693d6850b1d53 Mon Sep 17 00:00:00 2001
From: Bryan Boreham <bjboreham@gmail.com>
Date: Tue, 13 Mar 2018 17:16:56 +0000
Subject: [PATCH] Use pre-existing metric for log messages

---
 promrus.go | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/promrus.go b/promrus.go
index 2b435c1..dcde57f 100644
--- a/promrus.go
+++ b/promrus.go
@@ -24,13 +24,17 @@ func NewPrometheusHook() (*PrometheusHook, error) {
 	for _, level := range supportedLevels {
 		counterVec.WithLabelValues(level.String())
 	}
-	// Try to unregister the counter vector, in case already registered for some reason,
-	// e.g. double initialisation/configuration done by mistake by the end-user.
-	prometheus.Unregister(counterVec)
-	// Try to register the counter vector:
 	err := prometheus.Register(counterVec)
+	// If another library already registered the same metric, use it
 	if err != nil {
-		return nil, err
+		ar, ok := err.(prometheus.AlreadyRegisteredError)
+		if !ok {
+			return nil, err
+		}
+		counterVec, ok = ar.ExistingCollector.(*prometheus.CounterVec)
+		if !ok {
+			return nil, err
+		}
 	}
 	return &PrometheusHook{
 		counterVec: counterVec,