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Update ping input readme (influxdata#6412)
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147 changes: 98 additions & 49 deletions plugins/inputs/ping/README.md
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Sends a ping message by executing the system ping command and reports the results.

This plugin has two main methods of operation: `exec` and `native`. The
recommended method is `native`, which has greater system compatibility and
performance. However, for backwards compatibility the `exec` method is the
default.

When using `method = "exec"`, the systems ping utility is executed to send the
ping packets.

Most ping command implementations are supported, one notable exception being
that there is currently no support for GNU Inetutils ping. You may instead
use the iputils-ping implementation:
that there is currently no support for GNU Inetutils ping. You may instead use
the iputils-ping implementation:
```
apt-get install iputils-ping
```

When using `method = "native"` a ping is sent and the results are reported in pure go, eliminating the need to execute the system `ping` command. Not using the system binary allows the use of this plugin on non-english systems.

There is currently no support for TTL on windows with `"native"`; track progress at https://github.com/golang/go/issues/7175 and https://github.com/golang/go/issues/7174
When using `method = "native"` a ping is sent and the results are reported in
native Go by the Telegraf process, eliminating the need to execute the system
`ping` command.

### Configuration:

```toml
[[inputs.ping]]
## List of urls to ping
## Hosts to send ping packets to.
urls = ["example.org"]

## Number of pings to send per collection (ping -c <COUNT>)
## Method used for sending pings, can be either "exec" or "native". When set
## to "exec" the systems ping command will be executed. When set to "native"
## the plugin will send pings directly.
##
## While the default is "exec" for backwards compatibility, new deployments
## are encouraged to use the "native" method for improved compatibility and
## performance.
# method = "exec"

## Number of ping packets to send per interval. Corresponds to the "-c"
## option of the ping command.
# count = 1

## Interval, in s, at which to ping. 0 == default (ping -i <PING_INTERVAL>)
## Not available in Windows.
## Time to wait between sending ping packets in seconds. Operates like the
## "-i" option of the ping command.
# ping_interval = 1.0

## Per-ping timeout, in s. 0 == no timeout (ping -W <TIMEOUT>)
## If set, the time to wait for a ping response in seconds. Operates like
## the "-W" option of the ping command.
# timeout = 1.0

## Total-ping deadline, in s. 0 == no deadline (ping -w <DEADLINE>)
## If set, the total ping deadline, in seconds. Operates like the -w option
## of the ping command.
# deadline = 10

## Interface or source address to send ping from (ping -I <INTERFACE/SRC_ADDR>)
## on Darwin and Freebsd only source address possible: (ping -S <SRC_ADDR>)
## Interface or source address to send ping from. Operates like the -I or -S
## option of the ping command.
# interface = ""

## How to ping. "native" doesn't have external dependencies, while "exec" depends on 'ping'.
# method = "exec"

## Specify the ping executable binary, default is "ping"
## Specify the ping executable binary.
# binary = "ping"

## Arguments for ping command. When arguments is not empty, system binary will be used and
## other options (ping_interval, timeout, etc) will be ignored
## Arguments for ping command. When arguments is not empty, the command from
## the binary option will be used and other options (ping_interval, timeout,
## etc) will be ignored.
# arguments = ["-c", "3"]

## Use only ipv6 addresses when resolving hostnames.
## Use only IPv6 addresses when resolving a hostname.
# ipv6 = false
```

#### File Limit

Since this plugin runs the ping command, it may need to open several files per
host. With a large host list you may receive a `too many open files` error.
Since this plugin runs the ping command, it may need to open multiple files per
host. The number of files used is lessened with the `native` option but still
many files are used. With a large host list you may receive a `too many open
files` error.

To increase this limit on platforms using systemd it must be done in the
service file.
To increase this limit on platforms using systemd the recommended method is to
use the "drop-in directory", usually located at
`/etc/systemd/system/telegraf.service.d`.

You can create or edit a drop-in file in the correct location using:
```sh
$ systemctl edit telegraf
```

Find the service unit file:
Increase the number of open files:
```ini
[Service]
LimitNOFILE=8192
```
$ systemctl show telegraf.service -p FragmentPath
FragmentPath=/lib/systemd/system/telegraf.service

Restart Telegraf:
```sh
$ systemctl edit telegraf
```

Set the file number limit:
#### Linux Permissions

When using `method = "native"`, Telegraf will attempt to use privileged raw
ICMP sockets. On most systems, doing so requires `CAP_NET_RAW` capabilities.

With systemd:
```sh
$ systemctl edit telegraf
```
```ini
[Service]
LimitNOFILE=4096
CapabilityBoundingSet=CAP_NET_RAW
AmbientCapabilities=CAP_NET_RAW
```
```sh
$ systemctl restart telegraf
```

#### Permission Caveat (non Windows)
Without systemd:
```sh
$ setcap cap_net_raw=eip /usr/bin/telegraf
```

It is preferred that this plugin listen on privileged ICMP sockets. To do so, telegraf can either be run as the root user or the root user can add the capability to access raw sockets to telegraf by running the following commant:
Reference [`man 7 capabilities`][man 7 capabilities] for more information about
setting capabilities.

```
setcap cap_net_raw=eip /path/to/telegraf
```
[man 7 capabilities]: http://man7.org/linux/man-pages/man7/capabilities.7.html

Another option (doesn't work as well or in all circumstances) is to listen on unprivileged raw sockets (non-Windows only). The system group of the user running telegraf must be allowed to create ICMP Echo sockets. [See man pages icmp(7) for `ping_group_range`](http://man7.org/linux/man-pages/man7/icmp.7.html). On Linux hosts, run the following to give a group the proper permissions:
When Telegraf cannot listen on a privileged ICMP socket it will attempt to use
ICMP echo sockets. If you wish to use this method you must ensure Telegraf's
group, usually `telegraf`, is allowed to use ICMP echo sockets:

```sh
$ sysctl -w net.ipv4.ping_group_range="GROUP_ID_LOW GROUP_ID_HIGH"
```
sudo sysctl -w net.ipv4.ping_group_range="GROUP_ID_LOW GROUP_ID_HIGH"
```

Reference [`man 7 icmp`][man 7 icmp] for more information about ICMP echo
sockets and the `ping_group_range` setting.

[man 7 icmp]: http://man7.org/linux/man-pages/man7/icmp.7.html

### Metrics:
### Metrics

- ping
- tags:
Expand All @@ -102,24 +152,23 @@ sudo sysctl -w net.ipv4.ping_group_range="GROUP_ID_LOW GROUP_ID_HIGH"
- maximum_response_ms (integer)
- standard_deviation_ms (integer, Available on Windows only with native ping)
- errors (float, Windows only)
- reply_received (integer, Windows only*)
- percent_reply_loss (float, Windows only*)
- reply_received (integer, Windows with method = "exec" only)
- percent_reply_loss (float, Windows with method = "exec" only)
- result_code (int, success = 0, no such host = 1, ping error = 2)

##### reply_received vs packets_received

On Windows systems, "Destination net unreachable" reply will increment `packets_received` but not `reply_received`*
On Windows systems with `method = "exec"`, the "Destination net unreachable" reply will increment `packets_received` but not `reply_received`*.

### Example Output:
##### ttl

There is currently no support for TTL on windows with `"native"`; track
progress at https://github.com/golang/go/issues/7175 and
https://github.com/golang/go/issues/7174

**Windows:**
```
ping,url=example.org result_code=0i,average_response_ms=7i,maximum_response_ms=9i,minimum_response_ms=7i,packets_received=4i,packets_transmitted=4i,percent_packet_loss=0,percent_reply_loss=0,reply_received=4i 1469879119000000000
```

**Linux:**
### Example Output

```
ping,url=example.org average_response_ms=23.066,ttl=63,maximum_response_ms=24.64,minimum_response_ms=22.451,packets_received=5i,packets_transmitted=5i,percent_packet_loss=0,result_code=0i,standard_deviation_ms=0.809 1535747258000000000
```

*not when `method = "native"` is used
41 changes: 26 additions & 15 deletions plugins/inputs/ping/ping.go
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Expand Up @@ -11,7 +11,6 @@ import (
"time"

"github.com/glinton/ping"

"github.com/influxdata/telegraf"
"github.com/influxdata/telegraf/internal"
"github.com/influxdata/telegraf/plugins/inputs"
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}

const sampleConfig = `
## List of urls to ping
## Hosts to send ping packets to.
urls = ["example.org"]
## Number of pings to send per collection (ping -c <COUNT>)
## Method used for sending pings, can be either "exec" or "native". When set
## to "exec" the systems ping command will be executed. When set to "native"
## the plugin will send pings directly.
##
## While the default is "exec" for backwards compatibility, new deployments
## are encouraged to use the "native" method for improved compatibility and
## performance.
# method = "exec"
## Number of ping packets to send per interval. Corresponds to the "-c"
## option of the ping command.
# count = 1
## Interval, in s, at which to ping. 0 == default (ping -i <PING_INTERVAL>)
## Time to wait between sending ping packets in seconds. Operates like the
## "-i" option of the ping command.
# ping_interval = 1.0
## Per-ping timeout, in s. 0 == no timeout (ping -W <TIMEOUT>)
## If set, the time to wait for a ping response in seconds. Operates like
## the "-W" option of the ping command.
# timeout = 1.0
## Total-ping deadline, in s. 0 == no deadline (ping -w <DEADLINE>)
## If set, the total ping deadline, in seconds. Operates like the -w option
## of the ping command.
# deadline = 10
## Interface or source address to send ping from (ping -I[-S] <INTERFACE/SRC_ADDR>)
## Interface or source address to send ping from. Operates like the -I or -S
## option of the ping command.
# interface = ""
## How to ping. "native" doesn't have external dependencies, while "exec" depends on 'ping'.
# method = "exec"
## Specify the ping executable binary, default is "ping"
# binary = "ping"
## Specify the ping executable binary.
# binary = "ping"
## Arguments for ping command. When arguments is not empty, system binary will be used and
## other options (ping_interval, timeout, etc) will be ignored.
## Arguments for ping command. When arguments is not empty, the command from
## the binary option will be used and other options (ping_interval, timeout,
## etc) will be ignored.
# arguments = ["-c", "3"]
## Use only ipv6 addresses when resolving hostnames.
## Use only IPv6 addresses when resolving a hostname.
# ipv6 = false
`

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