Report non-fatal collection errors in the exporter metric. (#1439)

As per prometheus/client_golang#543, pass the Registry for exporter
metrics when setting up the /metrics HTTP handler.

With this, the `promhttp_metric_handler_errors_total` metric will
increment on (possibly non-fatal) collection-time errors, such as
duplicate metrics from text files.

Signed-off-by: Matthias Rampke <mr@soundcloud.com>

2 files changed, 8 insertions, 0 deletions

diff --git a/collector/fixtures/e2e-64k-page-output.txt b/collector/fixtures/e2e-64k-page-output.txt
index 8e9ba2c..14bd80d 100644
--- a/collector/fixtures/e2e-64k-page-output.txt
+++ b/collector/fixtures/e2e-64k-page-output.txt
@@ -3539,6 +3539,10 @@ node_zfs_zpool_wupdate{zpool="poolz1"} 1.10734831833266e+14
 # TYPE process_virtual_memory_bytes gauge
 # HELP process_virtual_memory_max_bytes Maximum amount of virtual memory available in bytes.
 # TYPE process_virtual_memory_max_bytes gauge
+# HELP promhttp_metric_handler_errors_total Total number of internal errors encountered by the promhttp metric handler.
+# TYPE promhttp_metric_handler_errors_total counter
+promhttp_metric_handler_errors_total{cause="encoding"} 0
+promhttp_metric_handler_errors_total{cause="gathering"} 0
 # HELP promhttp_metric_handler_requests_in_flight Current number of scrapes being served.
 # TYPE promhttp_metric_handler_requests_in_flight gauge
 promhttp_metric_handler_requests_in_flight 1
diff --git a/collector/fixtures/e2e-output.txt b/collector/fixtures/e2e-output.txt
index dab7df8..657856e 100644
--- a/collector/fixtures/e2e-output.txt
+++ b/collector/fixtures/e2e-output.txt
@@ -3539,6 +3539,10 @@ node_zfs_zpool_wupdate{zpool="poolz1"} 1.10734831833266e+14
 # TYPE process_virtual_memory_bytes gauge
 # HELP process_virtual_memory_max_bytes Maximum amount of virtual memory available in bytes.
 # TYPE process_virtual_memory_max_bytes gauge
+# HELP promhttp_metric_handler_errors_total Total number of internal errors encountered by the promhttp metric handler.
+# TYPE promhttp_metric_handler_errors_total counter
+promhttp_metric_handler_errors_total{cause="encoding"} 0
+promhttp_metric_handler_errors_total{cause="gathering"} 0
 # HELP promhttp_metric_handler_requests_in_flight Current number of scrapes being served.
 # TYPE promhttp_metric_handler_requests_in_flight gauge
 promhttp_metric_handler_requests_in_flight 1