add bcache plugin

Closes #286

CHANGELOG.md

@@ -27,6 +27,7 @@ of metrics collected and from how many plugins.
 - [#273](https://github.com/influxdb/telegraf/pull/273): puppet agent plugin, thats @jrxFive!
 - [#280](https://github.com/influxdb/telegraf/issues/280): Use InfluxDB client v2.
 - [#281](https://github.com/influxdb/telegraf/issues/281): Eliminate need to deep copy Batch Points.
+- [#286](https://github.com/influxdb/telegraf/issues/286): bcache plugin, thanks @cornerot!
 
 ### Bugfixes
 - [#228](https://github.com/influxdb/telegraf/pull/228): New version of package will replace old one. Thanks @ekini!

README.md

@@ -166,6 +166,7 @@ Below is how to configure `tagpass` and `tagdrop` parameters (added in 0.1.5)
 Telegraf currently has support for collecting metrics from
 
 * apache
+* bcache
 * disque
 * elasticsearch
 * exec (generic JSON-emitting executable plugin)

plugins/all/all.go

@@ -2,6 +2,7 @@ package all
 
 import (
 	_ "github.com/influxdb/telegraf/plugins/apache"
+	_ "github.com/influxdb/telegraf/plugins/bcache"
 	_ "github.com/influxdb/telegraf/plugins/disque"
 	_ "github.com/influxdb/telegraf/plugins/elasticsearch"
 	_ "github.com/influxdb/telegraf/plugins/exec"

plugins/bcache/README.md

@@ -0,0 +1,89 @@
+# Telegraf plugin: bcache
+
+Get bcache stat from stats_total directory and dirty_data file.
+
+# Measurements
+
+Meta:
+
+- tags: `backing_dev=dev bcache_dev=dev`
+
+Measurement names:
+
+- dirty_data
+- bypassed
+- cache_bypass_hits
+- cache_bypass_misses
+- cache_hit_ratio
+- cache_hits
+- cache_miss_collisions
+- cache_misses
+- cache_readaheads
+
+### Description
+
+```
+dirty_data
+  Amount of dirty data for this backing device in the cache. Continuously
+  updated unlike the cache set's version, but may be slightly off.
+  
+bypassed
+  Amount of IO (both reads and writes) that has bypassed the cache
+  
+
+cache_bypass_hits
+cache_bypass_misses
+  Hits and misses for IO that is intended to skip the cache are still counted,
+  but broken out here.
+  
+cache_hits
+cache_misses
+cache_hit_ratio
+  Hits and misses are counted per individual IO as bcache sees them; a
+  partial hit is counted as a miss.
+  
+cache_miss_collisions
+  Counts instances where data was going to be inserted into the cache from a
+  cache miss, but raced with a write and data was already present (usually 0
+  since the synchronization for cache misses was rewritten)
+  
+cache_readaheads
+  Count of times readahead occurred.
+```
+
+# Example output
+
+Using this configuration:
+
+```
+[bcache]
+  # Bcache sets path
+  # If not specified, then default is:
+  # bcachePath = "/sys/fs/bcache"
+  #
+  # By default, telegraf gather stats for all bcache devices
+  # Setting devices will restrict the stats to the specified
+  # bcache devices.
+  # bcacheDevs = ["bcache0", ...]
+```
+
+When run with:
+
+```
+./telegraf -config telegraf.conf -filter bcache -test
+```
+
+It produces:
+
+```
+* Plugin: bcache, Collection 1
+> [backing_dev="md10" bcache_dev="bcache0"] bcache_dirty_data value=11639194
+> [backing_dev="md10" bcache_dev="bcache0"] bcache_bypassed value=5167704440832
+> [backing_dev="md10" bcache_dev="bcache0"] bcache_cache_bypass_hits value=146270986
+> [backing_dev="md10" bcache_dev="bcache0"] bcache_cache_bypass_misses value=0
+> [backing_dev="md10" bcache_dev="bcache0"] bcache_cache_hit_ratio value=90
+> [backing_dev="md10" bcache_dev="bcache0"] bcache_cache_hits value=511941651
+> [backing_dev="md10" bcache_dev="bcache0"] bcache_cache_miss_collisions value=157678
+> [backing_dev="md10" bcache_dev="bcache0"] bcache_cache_misses value=50647396
+> [backing_dev="md10" bcache_dev="bcache0"] bcache_cache_readaheads value=0
+```

plugins/bcache/bcache.go

@@ -0,0 +1,144 @@
+package bcache
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+
+	"github.com/influxdb/telegraf/plugins"
+)
+
+type Bcache struct {
+	BcachePath string
+	BcacheDevs []string
+}
+
+var sampleConfig = `
+  # Bcache sets path
+  # If not specified, then default is:
+  # bcachePath = "/sys/fs/bcache"
+  #
+  # By default, telegraf gather stats for all bcache devices
+  # Setting devices will restrict the stats to the specified
+  # bcache devices.
+  # bcacheDevs = ["bcache0", ...]
+`
+
+func (b *Bcache) SampleConfig() string {
+	return sampleConfig
+}
+
+func (b *Bcache) Description() string {
+	return "Read metrics of bcache from stats_total and dirty_data"
+}
+
+func getBackingDevs(bcachePath string) []string {
+	bdevs, err := filepath.Glob(bcachePath + "/*/bdev*")
+	if len(bdevs) < 1 {
+		panic("Can't found any bcache device")
+	}
+	if err != nil {
+		panic(err)
+	}
+	return bdevs
+}
+
+func getTags(bdev string) map[string]string {
+	backingDevFile, _ := os.Readlink(bdev)
+	backingDevPath := strings.Split(backingDevFile, "/")
+	backingDev := backingDevPath[len(backingDevPath)-2]
+
+	bcacheDevFile, _ := os.Readlink(bdev + "/dev")
+	bcacheDevPath := strings.Split(bcacheDevFile, "/")
+	bcacheDev := bcacheDevPath[len(bcacheDevPath)-1]
+
+	return map[string]string{"backing_dev": backingDev, "bcache_dev": bcacheDev}
+}
+
+func prettyToBytes(v string) uint64 {
+	var factors = map[string]uint64{
+		"k": 1 << 10,
+		"M": 1 << 20,
+		"G": 1 << 30,
+		"T": 1 << 40,
+		"P": 1 << 50,
+		"E": 1 << 60,
+	}
+	var factor uint64
+	factor = 1
+	prefix := v[len(v)-1 : len(v)]
+	if factors[prefix] != 0 {
+		v = v[:len(v)-1]
+		factor = factors[prefix]
+	}
+	result, _ := strconv.ParseFloat(v, 32)
+	result = result * float64(factor)
+
+	return uint64(result)
+}
+
+func (b *Bcache) gatherBcache(bdev string, acc plugins.Accumulator) error {
+	tags := getTags(bdev)
+	metrics, err := filepath.Glob(bdev + "/stats_total/*")
+	if len(metrics) < 0 {
+		panic("Can't read any stats file")
+	}
+	file, err := ioutil.ReadFile(bdev + "/dirty_data")
+	if err != nil {
+		panic(err)
+	}
+	rawValue := strings.TrimSpace(string(file))
+	value := prettyToBytes(rawValue)
+	acc.Add("dirty_data", value, tags)
+
+	for _, path := range metrics {
+		key := filepath.Base(path)
+		file, err := ioutil.ReadFile(path)
+		rawValue := strings.TrimSpace(string(file))
+		if err != nil {
+			panic(err)
+		}
+		if key == "bypassed" {
+			value := prettyToBytes(rawValue)
+			acc.Add(key, value, tags)
+		} else {
+			value, _ := strconv.ParseUint(rawValue, 10, 64)
+			acc.Add(key, value, tags)
+		}
+	}
+	return nil
+}
+
+func (b *Bcache) Gather(acc plugins.Accumulator) error {
+	bcacheDevsChecked := make(map[string]bool)
+	var restrictDevs bool
+	if len(b.BcacheDevs) != 0 {
+		restrictDevs = true
+		for _, bcacheDev := range b.BcacheDevs {
+			bcacheDevsChecked[bcacheDev] = true
+		}
+	}
+
+	bcachePath := b.BcachePath
+	if len(bcachePath) == 0 {
+		bcachePath = "/sys/fs/bcache"
+	}
+	for _, bdev := range getBackingDevs(bcachePath) {
+		if restrictDevs {
+			bcacheDev := getTags(bdev)["bcache_dev"]
+			if !bcacheDevsChecked[bcacheDev] {
+				continue
+			}
+		}
+		b.gatherBcache(bdev, acc)
+	}
+	return nil
+}
+
+func init() {
+	plugins.Add("bcache", func() plugins.Plugin {
+		return &Bcache{}
+	})
+}