bcache: add priorityStats flag (#1621)HEADmaster

* bcache: add priorityStats flag

Fixes #1593

Signed-off-by: Aleksei Zakharov <zaharov@selectel.ru>

2 files changed, 34 insertions, 17 deletions

diff --git a/collector/bcache_linux.go b/collector/bcache_linux.go
index 20995c7..7941025 100644
--- a/collector/bcache_linux.go
+++ b/collector/bcache_linux.go
@@ -21,6 +21,11 @@ import (
         "github.com/go-kit/kit/log"
         "github.com/prometheus/client_golang/prometheus"
         "github.com/prometheus/procfs/bcache"
+        "gopkg.in/alecthomas/kingpin.v2"
+)
+
+var (
+        priorityStats = kingpin.Flag("collector.bcache.priorityStats", "Expose expensive priority stats.").Bool()
 )
 
 func init() {
@@ -50,7 +55,13 @@ func NewBcacheCollector(logger log.Logger) (Collector, error) {
 // Update reads and exposes bcache stats.
 // It implements the Collector interface.
 func (c *bcacheCollector) Update(ch chan<- prometheus.Metric) error {
-        stats, err := c.fs.Stats()
+        var stats []*bcache.Stats
+        var err error
+        if *priorityStats {
+                stats, err = c.fs.Stats()
+        } else {
+                stats, err = c.fs.StatsWithoutPriority()
+        }
         if err != nil {
                 return fmt.Errorf("failed to retrieve bcache stats: %w", err)
         }
@@ -259,23 +270,28 @@ func (c *bcacheCollector) updateBcacheStats(ch chan<- prometheus.Metric, s *bcac
                                 extraLabel:      []string{"cache_device"},
                                 extraLabelValue: cache.Name,
                         },
+                }
+                if *priorityStats {
                         // metrics in /sys/fs/bcache/<uuid>/<cache>/priority_stats
-                        {
-                                name:            "priority_stats_unused_percent",
-                                desc:            "The percentage of the cache that doesn't contain any data.",
-                                value:           float64(cache.Priority.UnusedPercent),
-                                metricType:      prometheus.GaugeValue,
-                                extraLabel:      []string{"cache_device"},
-                                extraLabelValue: cache.Name,
-                        },
-                        {
-                                name:            "priority_stats_metadata_percent",
-                                desc:            "Bcache's metadata overhead.",
-                                value:           float64(cache.Priority.MetadataPercent),
-                                metricType:      prometheus.GaugeValue,
-                                extraLabel:      []string{"cache_device"},
-                                extraLabelValue: cache.Name,
-                        },
+                        priorityStatsMetrics := []bcacheMetric{
+                                {
+                                        name:            "priority_stats_unused_percent",
+                                        desc:            "The percentage of the cache that doesn't contain any data.",
+                                        value:           float64(cache.Priority.UnusedPercent),
+                                        metricType:      prometheus.GaugeValue,
+                                        extraLabel:      []string{"cache_device"},
+                                        extraLabelValue: cache.Name,
+                                },
+                                {
+                                        name:            "priority_stats_metadata_percent",
+                                        desc:            "Bcache's metadata overhead.",
+                                        value:           float64(cache.Priority.MetadataPercent),
+                                        metricType:      prometheus.GaugeValue,
+                                        extraLabel:      []string{"cache_device"},
+                                        extraLabelValue: cache.Name,
+                                },
+                        }
+                        metrics = append(metrics, priorityStatsMetrics...)
                 }
                 allMetrics = append(allMetrics, metrics...)
         }
diff --git a/end-to-end-test.sh b/end-to-end-test.sh
index 955ab1d..2406061 100755
--- a/end-to-end-test.sh
+++ b/end-to-end-test.sh
@@ -106,6 +106,7 @@ fi
   --collector.wifi.fixtures="collector/fixtures/wifi" \
   --collector.qdisc.fixtures="collector/fixtures/qdisc/" \
   --collector.netclass.ignored-devices="(bond0|dmz|int)" \
+  --collector.bcache.priorityStats \
   --collector.cpu.info \
   --collector.cpu.info.flags-include="^(aes|avx.?|constant_tsc)$" \
   --collector.cpu.info.bugs-include="^(cpu_meltdown|spectre_.*|mds)$" \