Update changelog and tidy openntpd input

CHANGELOG.md

@@ -11,6 +11,7 @@
 
 - [docker_log](/plugins/inputs/docker_log) - Contributed by @prashanthjbabu
 - [fireboard](/plugins/inputs/fireboard) - Contributed by @ronnocol
+- [openntpd](/plugins/inputs/openntpd) - Contributed by @aromeyer
 - [uwsgi](/plugins/inputs/uswgi) - Contributed by @blaggacao
 
 #### New Parsers

plugins/inputs/openntpd/README.md

@@ -1,7 +1,8 @@
 # OpenNTPD Input Plugin
 
-Get standard NTP query metrics from OpenNTPD ([OpenNTPD - a FREE, easy to use
+Get standard NTP query metrics from [OpenNTPD][] using the ntpctl command.
-implementation of the Network Time Protocol](http://www.openntpd.org/)).
+
+[OpenNTPD]: http://www.openntpd.org/
 
 Below is the documentation of the various headers returned from the NTP query
 command when running `ntpctl -s peers`.
@@ -19,40 +20,36 @@ the remote peer or server (RMS, milliseconds);
 - jitter – Mean deviation (jitter) in the time reported for that remote peer or
 server (RMS of difference of multiple time samples, milliseconds);
 
-### Configuration:
+### Configuration
 
 ```toml
-# Get standard NTP query metrics, requires ntpctls executable
-# provided by openntpd packages
 [[inputs.openntpd]]
-  ## If running as a restricted user you can prepend sudo for additional access:
+  ## Run ntpctl binary with sudo.
-  #use_sudo = false
+  # use_sudo = false
 
-  ## The default location of the ntpctl binary can be overridden with:
+  ## Location of the ntpctl binary.
-  binary = "/usr/sbin/ntpctl"
+  # binary = "/usr/sbin/ntpctl"
 
-  ## The default timeout of 1000ms can be overriden with (in milliseconds):
+  ## Maximum time the ntpctl binary is allowed to run.
-  #timeout = 1000
+  # timeout = "5ms"
 ```
 
-### Measurements & Fields:
+### Metrics
 
 - ntpctl
-  - delay (float, milliseconds)
+  - tags:
-  - jitter (float, milliseconds)
+    - remote
-  - offset (float, milliseconds)
+    - stratum
-  - poll (int, seconds)
+  - fields:
-  - next (int,,seconds)
+    - delay (float, milliseconds)
-  - wt (int)
+    - jitter (float, milliseconds)
-  - tl (int)
+    - offset (float, milliseconds)
+    - poll (int, seconds)
+    - next (int, seconds)
+    - wt (int)
+    - tl (int)
 
-### Tags:
+### Permissions
-
-- All measurements have the following tags:
-  - remote
-  - stratum
-
-### Permissions:
 
 It's important to note that this plugin references ntpctl, which may require
 additional permissions to execute successfully.
@@ -80,17 +77,17 @@ If you use this method, you will need the following in your telegraf config:
 You will also need to update your sudoers file:
 ```bash
 $ visudo
-# Add the following line:
+# Add the following lines:
-telegraf ALL=(ALL) NOPASSWD: /usr/sbin/ntpctl
+Cmnd_Alias NTPCTL = /usr/sbin/ntpctl
+telegraf ALL=(ALL) NOPASSWD: NTPCTL
+Defaults!NTPCTL !logfile, !syslog, !pam_session
 ```
 
 Please use the solution you see as most appropriate.
 
-### Example Output:
+### Example Output
 
 ```
-$ telegraf --config ~/ws/telegraf.conf --input-filter openntpd --test
+openntpd,remote=194.57.169.1,stratum=2,host=localhost tl=10i,poll=1007i,
-* Plugin: openntpd, Collection 1
-> openntpd,remote=194.57.169.1,stratum=2,host=localhost tl=10i,poll=1007i,
 offset=2.295,jitter=3.896,delay=53.766,next=266i,wt=1i 1514454299000000000
 ```

plugins/inputs/openntpd/openntpd.go

@@ -53,7 +53,7 @@ type Openntpd struct {
 }
 
 var defaultBinary = "/usr/sbin/ntpctl"
-var defaultTimeout = internal.Duration{Duration: time.Second}
+var defaultTimeout = internal.Duration{Duration: 5 * time.Second}
 
 func (n *Openntpd) Description() string {
 	return "Get standard NTP query metrics from OpenNTPD."
@@ -61,14 +61,14 @@ func (n *Openntpd) Description() string {
 
 func (n *Openntpd) SampleConfig() string {
 	return `
-  ## If running as a restricted user you can prepend sudo for additional access:
+  ## Run ntpctl binary with sudo.
-  #use_sudo = false
+  # use_sudo = false
 
-  ## The default location of the ntpctl binary can be overridden with:
+  ## Location of the ntpctl binary.
-  binary = "/usr/sbin/ntpctl"
+  # binary = "/usr/sbin/ntpctl"
 
-  ## The default timeout of 1000ms can be overriden with (in milliseconds):
+  ## Maximum time the ntpctl binary is allowed to run.
-  timeout = 1000
+  # timeout = "5ms"
   `
 }
 
@@ -135,12 +135,12 @@ func (n *Openntpd) Gather(acc telegraf.Accumulator) error {
 		// if there is an ntpctl state prefix, remove it and make it it's own tag
 		if strings.ContainsAny(string(fields[0]), "*") {
 			tags["state_prefix"] = string(fields[0])
-			fields = append(fields[:0], fields[1:]...)
+			fields = fields[1:]
 		}
 
 		// Get tags from output
 		for key, index := range tagI {
-			if len(fields) < index {
+			if index >= len(fields) {
 				continue
 			}
 			tags[key] = fields[index]