Adding a conntrack input plugin

- Collects conntrack stats from the configured directories and files.

Applying PR feedback:

- Rebased onto master
- Updated README/CHANGELOG
- Limited lines to 80 chars
- Improved plugin docs and README
- added a dummy notlinux build file

Fixed up CHANGELOG and README after rebase

closes #1164

CHANGELOG.md

@@ -19,6 +19,7 @@ time before a new metric is included by the plugin.
 
 ### Features
 
+- [#1164](https://github.com/influxdata/telegraf/pull/1164): conntrack input plugin. Thanks @robinpercy!
 - [#1247](https://github.com/influxdata/telegraf/pull/1247): rollbar input plugin. Thanks @francois2metz and @cduez!
 - [#1208](https://github.com/influxdata/telegraf/pull/1208): Standardized AWS credentials evaluation & wildcard CloudWatch dimensions. Thanks @johnrengelman!
 - [#1264](https://github.com/influxdata/telegraf/pull/1264): Add SSL config options to http_response plugin.

README.md

@@ -145,6 +145,7 @@ Currently implemented sources:
 * [cassandra](https://github.com/influxdata/telegraf/tree/master/plugins/inputs/cassandra)
 * [ceph](https://github.com/influxdata/telegraf/tree/master/plugins/inputs/ceph)
 * [chrony](https://github.com/influxdata/telegraf/tree/master/plugins/inputs/chrony)
+* [conntrack](https://github.com/influxdata/telegraf/tree/master/plugins/inputs/conntrack)
 * [couchbase](https://github.com/influxdata/telegraf/tree/master/plugins/inputs/couchbase)
 * [couchdb](https://github.com/influxdata/telegraf/tree/master/plugins/inputs/couchdb)
 * [disque](https://github.com/influxdata/telegraf/tree/master/plugins/inputs/disque)

etc/telegraf.conf

@@ -1575,3 +1575,13 @@
 #   ## https://github.com/influxdata/telegraf/blob/master/docs/DATA_FORMATS_INPUT.md
 #   data_format = "influx"
 
+# # Collects conntrack stats from the configured directories and files.
+# [[inputs.conntrack]]
+#   ## The following defaults would work with multiple versions of contrack. Note the nf_ and ip_
+#   ## filename prefixes are mutually exclusive across conntrack versions, as are the directory locations.
+#
+#   ## Superset of filenames to look for within the conntrack dirs. Missing files will be ignored.
+#   files = ["ip_conntrack_count","ip_conntrack_max","nf_conntrack_count","nf_conntrack_max"]
+#
+#   ## Directories to search within for the conntrack files above. Missing directrories will be ignored.
+#   dirs = ["/proc/sys/net/ipv4/netfilter","/proc/sys/net/netfilter"]

plugins/inputs/all/all.go

@@ -8,6 +8,7 @@ import (
 	_ "github.com/influxdata/telegraf/plugins/inputs/ceph"
 	_ "github.com/influxdata/telegraf/plugins/inputs/chrony"
 	_ "github.com/influxdata/telegraf/plugins/inputs/cloudwatch"
+	_ "github.com/influxdata/telegraf/plugins/inputs/conntrack"
 	_ "github.com/influxdata/telegraf/plugins/inputs/couchbase"
 	_ "github.com/influxdata/telegraf/plugins/inputs/couchdb"
 	_ "github.com/influxdata/telegraf/plugins/inputs/disque"

plugins/inputs/conntrack/README.md

@@ -0,0 +1,56 @@
+# Conntrack Plugin
+
+Collects stats from Netfilter's conntrack-tools.
+
+The conntrack-tools provide a mechanism for tracking various aspects of
+network connections as they are processed by netfilter. At runtime, 
+conntrack exposes many of those connection statistics within /proc/sys/net.
+Depending on your kernel version, these files can be found in either
+/proc/sys/net/ipv4/netfilter or /proc/sys/net/netfilter and will be
+prefixed with either ip_ or nf_.  This plugin reads the files specified 
+in its configuration and publishes each one as a field, with the prefix
+normalized to ip_.  
+
+In order to simplify configuration in a heterogeneous environment, a superset
+of directory and filenames can be specified.  Any locations that don't exist
+will be ignored.
+
+For more information on conntrack-tools, see the 
+[Netfilter Documentation](http://conntrack-tools.netfilter.org/).
+
+
+### Configuration:
+
+```toml
+ # Collects conntrack stats from the configured directories and files.
+ [[inputs.conntrack]]
+   ## The following defaults would work with multiple versions of conntrack.
+   ## Note the nf_ and ip_ filename prefixes are mutually exclusive across
+   ## kernel versions, as are the directory locations.
+
+   ## Superset of filenames to look for within the conntrack dirs.
+   ## Missing files will be ignored.
+   files = ["ip_conntrack_count","ip_conntrack_max",
+            "nf_conntrack_count","nf_conntrack_max"]
+
+   ## Directories to search within for the conntrack files above.
+   ## Missing directrories will be ignored.
+   dirs = ["/proc/sys/net/ipv4/netfilter","/proc/sys/net/netfilter"]
+```
+
+### Measurements & Fields:
+
+- conntrack
+    - ip_conntrack_count (int, count): the number of entries in the conntrack table 
+    - ip_conntrack_max (int, size): the max capacity of the conntrack table
+
+### Tags:
+
+This input does not use tags.
+
+### Example Output:
+
+```
+$ ./telegraf -config telegraf.conf -input-filter conntrack -test
+conntrack,host=myhost ip_conntrack_count=2,ip_conntrack_max=262144 1461620427667995735
+```

plugins/inputs/conntrack/conntrack.go

@@ -0,0 +1,119 @@
+// +build linux
+
+package conntrack
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"strconv"
+	"strings"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/plugins/inputs"
+	"log"
+	"path/filepath"
+)
+
+type Conntrack struct {
+	Path  string
+	Dirs  []string
+	Files []string
+}
+
+const (
+	inputName = "conntrack"
+)
+
+var dfltDirs = []string{
+	"/proc/sys/net/ipv4/netfilter",
+	"/proc/sys/net/netfilter",
+}
+
+var dfltFiles = []string{
+	"ip_conntrack_count",
+	"ip_conntrack_max",
+	"nf_conntrack_count",
+	"nf_conntrack_max",
+}
+
+func (c *Conntrack) setDefaults() {
+	if len(c.Dirs) == 0 {
+		c.Dirs = dfltDirs
+	}
+
+	if len(c.Files) == 0 {
+		c.Files = dfltFiles
+	}
+}
+
+func (c *Conntrack) Description() string {
+	return "Collects conntrack stats from the configured directories and files."
+}
+
+var sampleConfig = `
+   ## The following defaults would work with multiple versions of conntrack.
+   ## Note the nf_ and ip_ filename prefixes are mutually exclusive across
+   ## kernel versions, as are the directory locations.
+
+   ## Superset of filenames to look for within the conntrack dirs.
+   ## Missing files will be ignored.
+   files = ["ip_conntrack_count","ip_conntrack_max",
+            "nf_conntrack_count","nf_conntrack_max"]
+
+   ## Directories to search within for the conntrack files above.
+   ## Missing directrories will be ignored.
+   dirs = ["/proc/sys/net/ipv4/netfilter","/proc/sys/net/netfilter"]
+`
+
+func (c *Conntrack) SampleConfig() string {
+	return sampleConfig
+}
+
+func (c *Conntrack) Gather(acc telegraf.Accumulator) error {
+	c.setDefaults()
+
+	var metricKey string
+	fields := make(map[string]interface{})
+
+	for _, dir := range c.Dirs {
+		for _, file := range c.Files {
+			// NOTE: no system will have both nf_ and ip_ prefixes,
+			// so we're safe to branch on suffix only.
+			parts := strings.SplitN(file, "_", 2)
+			if len(parts) < 2 {
+				continue
+			}
+			metricKey = "ip_" + parts[1]
+
+			fName := filepath.Join(dir, file)
+			if _, err := os.Stat(fName); err != nil {
+				continue
+			}
+
+			contents, err := ioutil.ReadFile(fName)
+			if err != nil {
+				log.Printf("failed to read file '%s': %v", fName, err)
+			}
+
+			v := strings.TrimSpace(string(contents))
+			fields[metricKey], err = strconv.ParseFloat(v, 64)
+			if err != nil {
+				log.Printf("failed to parse metric, expected number but "+
+					" found '%s': %v", v, err)
+			}
+		}
+	}
+
+	if len(fields) == 0 {
+		return fmt.Errorf("Conntrack input failed to collect metrics. " +
+			"Is the conntrack kernel module loaded?")
+	}
+
+	acc.AddFields(inputName, fields, nil)
+	return nil
+}
+
+func init() {
+	inputs.Add(inputName, func() telegraf.Input { return &Conntrack{} })
+}

plugins/inputs/conntrack/conntrack_notlinux.go

@@ -0,0 +1,3 @@
+// +build !linux
+
+package conntrack

plugins/inputs/conntrack/conntrack_test.go

@@ -0,0 +1,90 @@
+// +build linux
+
+package conntrack
+
+import (
+	"github.com/influxdata/telegraf/testutil"
+	"github.com/stretchr/testify/assert"
+	"io/ioutil"
+	"os"
+	"path"
+	"strconv"
+	"strings"
+	"testing"
+)
+
+func restoreDflts(savedFiles, savedDirs []string) {
+	dfltFiles = savedFiles
+	dfltDirs = savedDirs
+}
+
+func TestNoFilesFound(t *testing.T) {
+	defer restoreDflts(dfltFiles, dfltDirs)
+
+	dfltFiles = []string{"baz.txt"}
+	dfltDirs = []string{"./foo/bar"}
+	c := &Conntrack{}
+	acc := &testutil.Accumulator{}
+	err := c.Gather(acc)
+
+	assert.EqualError(t, err, "Conntrack input failed to collect metrics. "+
+		"Is the conntrack kernel module loaded?")
+}
+
+func TestDefaultsUsed(t *testing.T) {
+	defer restoreDflts(dfltFiles, dfltDirs)
+	tmpdir, err := ioutil.TempDir("", "tmp1")
+	assert.NoError(t, err)
+	defer os.Remove(tmpdir)
+
+	tmpFile, err := ioutil.TempFile(tmpdir, "ip_conntrack_count")
+	assert.NoError(t, err)
+
+	dfltDirs = []string{tmpdir}
+	fname := path.Base(tmpFile.Name())
+	dfltFiles = []string{fname}
+
+	count := 1234321
+	ioutil.WriteFile(tmpFile.Name(), []byte(strconv.Itoa(count)), 0660)
+	c := &Conntrack{}
+	acc := &testutil.Accumulator{}
+
+	c.Gather(acc)
+	acc.AssertContainsFields(t, inputName, map[string]interface{}{
+		fname: float64(count)})
+}
+
+func TestConfigsUsed(t *testing.T) {
+	defer restoreDflts(dfltFiles, dfltDirs)
+	tmpdir, err := ioutil.TempDir("", "tmp1")
+	assert.NoError(t, err)
+	defer os.Remove(tmpdir)
+
+	cntFile, err := ioutil.TempFile(tmpdir, "nf_conntrack_count")
+	maxFile, err := ioutil.TempFile(tmpdir, "nf_conntrack_max")
+	assert.NoError(t, err)
+
+	dfltDirs = []string{tmpdir}
+	cntFname := path.Base(cntFile.Name())
+	maxFname := path.Base(maxFile.Name())
+	dfltFiles = []string{cntFname, maxFname}
+
+	count := 1234321
+	max := 9999999
+	ioutil.WriteFile(cntFile.Name(), []byte(strconv.Itoa(count)), 0660)
+	ioutil.WriteFile(maxFile.Name(), []byte(strconv.Itoa(max)), 0660)
+	c := &Conntrack{}
+	acc := &testutil.Accumulator{}
+
+	c.Gather(acc)
+
+	fix := func(s string) string {
+		return strings.Replace(s, "nf_", "ip_", 1)
+	}
+
+	acc.AssertContainsFields(t, inputName,
+		map[string]interface{}{
+			fix(cntFname): float64(count),
+			fix(maxFname): float64(max),
+		})
+}