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3b035c8fa1
* bcache: add priorityStats flag Fixes #1593 Signed-off-by: Aleksei Zakharov <zaharov@selectel.ru>
322 lines
9.7 KiB
Go
322 lines
9.7 KiB
Go
// Copyright 2017 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// +build !nobcache
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package collector
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import (
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"fmt"
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"github.com/go-kit/kit/log"
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"github.com/prometheus/client_golang/prometheus"
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"github.com/prometheus/procfs/bcache"
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"gopkg.in/alecthomas/kingpin.v2"
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)
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var (
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priorityStats = kingpin.Flag("collector.bcache.priorityStats", "Expose expensive priority stats.").Bool()
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)
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func init() {
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registerCollector("bcache", defaultEnabled, NewBcacheCollector)
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}
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// A bcacheCollector is a Collector which gathers metrics from Linux bcache.
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type bcacheCollector struct {
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fs bcache.FS
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logger log.Logger
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}
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// NewBcacheCollector returns a newly allocated bcacheCollector.
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// It exposes a number of Linux bcache statistics.
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func NewBcacheCollector(logger log.Logger) (Collector, error) {
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fs, err := bcache.NewFS(*sysPath)
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if err != nil {
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return nil, fmt.Errorf("failed to open sysfs: %w", err)
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}
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return &bcacheCollector{
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fs: fs,
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logger: logger,
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}, nil
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}
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// Update reads and exposes bcache stats.
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// It implements the Collector interface.
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func (c *bcacheCollector) Update(ch chan<- prometheus.Metric) error {
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var stats []*bcache.Stats
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var err error
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if *priorityStats {
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stats, err = c.fs.Stats()
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} else {
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stats, err = c.fs.StatsWithoutPriority()
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}
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if err != nil {
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return fmt.Errorf("failed to retrieve bcache stats: %w", err)
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}
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for _, s := range stats {
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c.updateBcacheStats(ch, s)
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}
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return nil
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}
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type bcacheMetric struct {
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name string
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desc string
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value float64
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metricType prometheus.ValueType
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extraLabel []string
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extraLabelValue string
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}
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func bcachePeriodStatsToMetric(ps *bcache.PeriodStats, labelValue string) []bcacheMetric {
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label := []string{"backing_device"}
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metrics := []bcacheMetric{
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{
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name: "bypassed_bytes_total",
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desc: "Amount of IO (both reads and writes) that has bypassed the cache.",
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value: float64(ps.Bypassed),
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metricType: prometheus.CounterValue,
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extraLabel: label,
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extraLabelValue: labelValue,
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},
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{
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name: "cache_hits_total",
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desc: "Hits counted per individual IO as bcache sees them.",
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value: float64(ps.CacheHits),
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metricType: prometheus.CounterValue,
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extraLabel: label,
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extraLabelValue: labelValue,
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},
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{
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name: "cache_misses_total",
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desc: "Misses counted per individual IO as bcache sees them.",
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value: float64(ps.CacheMisses),
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metricType: prometheus.CounterValue,
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extraLabel: label,
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extraLabelValue: labelValue,
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},
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{
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name: "cache_bypass_hits_total",
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desc: "Hits for IO intended to skip the cache.",
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value: float64(ps.CacheBypassHits),
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metricType: prometheus.CounterValue,
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extraLabel: label,
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extraLabelValue: labelValue,
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},
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{
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name: "cache_bypass_misses_total",
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desc: "Misses for IO intended to skip the cache.",
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value: float64(ps.CacheBypassMisses),
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metricType: prometheus.CounterValue,
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extraLabel: label,
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extraLabelValue: labelValue,
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},
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{
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name: "cache_miss_collisions_total",
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desc: "Instances where data insertion from cache miss raced with write (data already present).",
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value: float64(ps.CacheMissCollisions),
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metricType: prometheus.CounterValue,
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extraLabel: label,
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extraLabelValue: labelValue,
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},
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{
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name: "cache_readaheads_total",
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desc: "Count of times readahead occurred.",
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value: float64(ps.CacheReadaheads),
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metricType: prometheus.CounterValue,
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extraLabel: label,
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extraLabelValue: labelValue,
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},
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}
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return metrics
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}
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// UpdateBcacheStats collects statistics for one bcache ID.
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func (c *bcacheCollector) updateBcacheStats(ch chan<- prometheus.Metric, s *bcache.Stats) {
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const (
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subsystem = "bcache"
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)
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var (
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devLabel = []string{"uuid"}
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allMetrics []bcacheMetric
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metrics []bcacheMetric
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)
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allMetrics = []bcacheMetric{
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// metrics in /sys/fs/bcache/<uuid>/
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{
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name: "average_key_size_sectors",
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desc: "Average data per key in the btree (sectors).",
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value: float64(s.Bcache.AverageKeySize),
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metricType: prometheus.GaugeValue,
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},
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{
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name: "btree_cache_size_bytes",
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desc: "Amount of memory currently used by the btree cache.",
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value: float64(s.Bcache.BtreeCacheSize),
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metricType: prometheus.GaugeValue,
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},
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{
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name: "cache_available_percent",
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desc: "Percentage of cache device without dirty data, usable for writeback (may contain clean cached data).",
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value: float64(s.Bcache.CacheAvailablePercent),
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metricType: prometheus.GaugeValue,
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},
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{
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name: "congested",
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desc: "Congestion.",
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value: float64(s.Bcache.Congested),
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metricType: prometheus.GaugeValue,
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},
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{
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name: "root_usage_percent",
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desc: "Percentage of the root btree node in use (tree depth increases if too high).",
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value: float64(s.Bcache.RootUsagePercent),
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metricType: prometheus.GaugeValue,
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},
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{
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name: "tree_depth",
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desc: "Depth of the btree.",
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value: float64(s.Bcache.TreeDepth),
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metricType: prometheus.GaugeValue,
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},
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// metrics in /sys/fs/bcache/<uuid>/internal/
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{
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name: "active_journal_entries",
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desc: "Number of journal entries that are newer than the index.",
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value: float64(s.Bcache.Internal.ActiveJournalEntries),
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metricType: prometheus.GaugeValue,
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},
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{
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name: "btree_nodes",
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desc: "Total nodes in the btree.",
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value: float64(s.Bcache.Internal.BtreeNodes),
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metricType: prometheus.GaugeValue,
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},
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{
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name: "btree_read_average_duration_seconds",
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desc: "Average btree read duration.",
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value: float64(s.Bcache.Internal.BtreeReadAverageDurationNanoSeconds) * 1e-9,
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metricType: prometheus.GaugeValue,
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},
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{
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name: "cache_read_races_total",
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desc: "Counts instances where while data was being read from the cache, the bucket was reused and invalidated - i.e. where the pointer was stale after the read completed.",
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value: float64(s.Bcache.Internal.CacheReadRaces),
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metricType: prometheus.CounterValue,
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},
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}
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for _, bdev := range s.Bdevs {
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// metrics in /sys/fs/bcache/<uuid>/<bdev>/
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metrics = []bcacheMetric{
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{
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name: "dirty_data_bytes",
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desc: "Amount of dirty data for this backing device in the cache.",
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value: float64(bdev.DirtyData),
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metricType: prometheus.GaugeValue,
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extraLabel: []string{"backing_device"},
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extraLabelValue: bdev.Name,
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},
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}
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allMetrics = append(allMetrics, metrics...)
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// metrics in /sys/fs/bcache/<uuid>/<bdev>/stats_total
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metrics := bcachePeriodStatsToMetric(&bdev.Total, bdev.Name)
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allMetrics = append(allMetrics, metrics...)
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}
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for _, cache := range s.Caches {
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metrics = []bcacheMetric{
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// metrics in /sys/fs/bcache/<uuid>/<cache>/
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{
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name: "io_errors",
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desc: "Number of errors that have occurred, decayed by io_error_halflife.",
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value: float64(cache.IOErrors),
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metricType: prometheus.GaugeValue,
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extraLabel: []string{"cache_device"},
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extraLabelValue: cache.Name,
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},
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{
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name: "metadata_written_bytes_total",
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desc: "Sum of all non data writes (btree writes and all other metadata).",
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value: float64(cache.MetadataWritten),
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metricType: prometheus.CounterValue,
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extraLabel: []string{"cache_device"},
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extraLabelValue: cache.Name,
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},
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{
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name: "written_bytes_total",
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desc: "Sum of all data that has been written to the cache.",
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value: float64(cache.Written),
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metricType: prometheus.CounterValue,
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extraLabel: []string{"cache_device"},
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extraLabelValue: cache.Name,
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},
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}
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if *priorityStats {
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// metrics in /sys/fs/bcache/<uuid>/<cache>/priority_stats
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priorityStatsMetrics := []bcacheMetric{
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{
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name: "priority_stats_unused_percent",
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desc: "The percentage of the cache that doesn't contain any data.",
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value: float64(cache.Priority.UnusedPercent),
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metricType: prometheus.GaugeValue,
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extraLabel: []string{"cache_device"},
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extraLabelValue: cache.Name,
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},
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{
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name: "priority_stats_metadata_percent",
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desc: "Bcache's metadata overhead.",
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value: float64(cache.Priority.MetadataPercent),
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metricType: prometheus.GaugeValue,
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extraLabel: []string{"cache_device"},
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extraLabelValue: cache.Name,
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},
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}
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metrics = append(metrics, priorityStatsMetrics...)
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}
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allMetrics = append(allMetrics, metrics...)
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}
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for _, m := range allMetrics {
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labels := append(devLabel, m.extraLabel...)
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desc := prometheus.NewDesc(
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prometheus.BuildFQName(namespace, subsystem, m.name),
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m.desc,
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labels,
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nil,
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)
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labelValues := []string{s.Name}
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if m.extraLabelValue != "" {
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labelValues = append(labelValues, m.extraLabelValue)
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}
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ch <- prometheus.MustNewConstMetric(
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desc,
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m.metricType,
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m.value,
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labelValues...,
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)
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}
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}
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