From 62c76c4ced042f9ec3710fd9105ae62c386d8119 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jakub=20Soko=C5=82owski?= <jakub@status.im>
Date: Thu, 11 Jul 2019 13:42:56 -0400
Subject: [PATCH] allow the metrics call to fail
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Starting from 1.9.0 Geth removed the `debug_metrics` RPC call

Signed-off-by: Jakub Sokołowski <jakub@status.im>
---
 README.md    |  2 ++
 collector.go | 18 +++++++++++-------
 metrics.go   |  2 ++
 3 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/README.md b/README.md
index 3a1947b..0877f24 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,5 @@
+# WARNING: This software is deprecated since Geth `1.9.0` which introduced its own [Prometheus endpoint](https://blog.ethereum.org/2019/07/10/geth-v1-9-0/#metrics-collection).
+
 # geth_exporter
 
 `geth_exporter` is a metrics exporter for [Prometheus](https://github.com/prometheus/prometheus).
diff --git a/collector.go b/collector.go
index c3ba728..7253261 100644
--- a/collector.go
+++ b/collector.go
@@ -39,18 +39,22 @@ func (c *collector) collect() (flatMetrics, error) {
 
 	m, err := cl.metrics()
 	if err != nil {
-		return nil, err
+		/* not all geth nodes have debug enabled, s might be nil */
+		log.Printf("failed to get metrics: %v", err)
 	}
 
+	/* can handle m being nil, will just return an empty flatMetrics */
 	all := transformMetrics(m)
 
-	/* optional syncing stats */
 	s, err := cl.syncingMetrics()
-	if err == nil {
-		sync := decodeSyncData(s, "sync_")
-		for k, v := range sync {
-			all[k] = v
-		}
+	if err != nil {
+		/* not all geth nodes have eth enabled, s might be nil */
+		log.Printf("failed to get syncing stats: %v", err)
+	}
+
+	sync := decodeSyncData(s, "sync_")
+	for k, v := range sync {
+		all[k] = v
 	}
 
 	for k := range all {
diff --git a/metrics.go b/metrics.go
index 6fb685e..3fcdbea 100644
--- a/metrics.go
+++ b/metrics.go
@@ -34,6 +34,8 @@ func transformMetrics(data metrics) flatMetrics {
 	return flattenMetrics(data, make(flatMetrics), "")
 }
 
+/* flattenMetrics can handle data being nil, it will just return memo.
+ * A range over a nil slice is like a range over an empty slice. */
 func flattenMetrics(data metrics, memo flatMetrics, prefix string) flatMetrics {
 	for k, v := range data {
 		key := prefix + normalizeKey(k)