Applying PR feedback:

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

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ### Features
 
+- [#1164](https://github.com/influxdata/telegraf/pull/1164): conntrack input plugin. Thanks @robinpercy!
 - [#1138](https://github.com/influxdata/telegraf/pull/1138): nstat input plugin. Thanks @Maksadbek!
 - [#1139](https://github.com/influxdata/telegraf/pull/1139): instrumental output plugin. Thanks @jasonroelofs!
 - [#1172](https://github.com/influxdata/telegraf/pull/1172): Ceph storage stats. Thanks @robinpercy!

README.md

@@ -162,6 +162,7 @@ Currently implemented sources:
 * [bcache](https://github.com/influxdata/telegraf/tree/master/plugins/inputs/bcache)
 * [cassandra](https://github.com/influxdata/telegraf/tree/master/plugins/inputs/cassandra)
 * [ceph](https://github.com/influxdata/telegraf/tree/master/plugins/inputs/ceph)
+* [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)

plugins/inputs/conntrack/README.md

@@ -1,19 +1,40 @@
 # Conntrack Plugin
 
-Collects conntrack stats from the configured directories and files.
+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 contrack. Note the nf_ and ip_
-   ## filename prefixes are mutually exclusive across conntrack versions, as are the directory locations.
+   ## 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"]
+   ## 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.
+   ## 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/conntrack/conntrack.go

@@ -1,3 +1,5 @@
+// +build !windows
+
 package conntrack
 
 import (
@@ -50,15 +52,17 @@ func (c *Conntrack) Description() string {
 }
 
 var sampleConfig = `
- # 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.
+   ## 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"]
+   ## 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.
+   ## Directories to search within for the conntrack files above.
+   ## Missing directrories will be ignored.
    dirs = ["/proc/sys/net/ipv4/netfilter","/proc/sys/net/netfilter"]
 `
 
@@ -74,7 +78,8 @@ func (c *Conntrack) Gather(acc telegraf.Accumulator) error {
 
 	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.
+			// 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
@@ -94,13 +99,15 @@ func (c *Conntrack) Gather(acc telegraf.Accumulator) error {
 			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)
+				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?")
+		return fmt.Errorf("Conntrack input failed to collect metrics. " +
+			"Is the conntrack kernel module loaded?")
 	}
 
 	acc.AddFields(inputName, fields, nil)

plugins/inputs/conntrack/conntrack_test.go

@@ -1,3 +1,5 @@
+// +build !windows
+
 package conntrack
 
 import (
@@ -25,7 +27,8 @@ func TestNoFilesFound(t *testing.T) {
 	acc := &testutil.Accumulator{}
 	err := c.Gather(acc)
 
-	assert.EqualError(t, err, "Conntrack input failed to collect metrics. Is the conntrack kernel module loaded?")
+	assert.EqualError(t, err, "Conntrack input failed to collect metrics. "+
+		"Is the conntrack kernel module loaded?")
 }
 
 func TestDefaultsUsed(t *testing.T) {
@@ -47,7 +50,8 @@ func TestDefaultsUsed(t *testing.T) {
 	acc := &testutil.Accumulator{}
 
 	c.Gather(acc)
-	acc.AssertContainsFields(t, inputName, map[string]interface{}{fname: float64(count)})
+	acc.AssertContainsFields(t, inputName, map[string]interface{}{
+		fname: float64(count)})
 }
 
 func TestConfigsUsed(t *testing.T) {

plugins/inputs/conntrack/conntrack_windows.go

@@ -0,0 +1,3 @@
+// +build windows
+
+package conntrack