Design goals are to have a minimal memory footprint with a plugin system so that developers in the community can easily add support for collecting metrics from well known services (like Hadoop, or Postgres, or Redis) and third party APIs (like Mailchimp, AWS CloudWatch, or Google Analytics).
We'll eagerly accept pull requests for new plugins and will manage the set of plugins that Telegraf supports. See the bottom of this doc for instructions on writing new plugins.
Telegraf has a few options you can configure under the `agent` section of the config. If you don't see an `agent` section run `telegraf -sample-config > telegraf.toml` to create a valid initial configuration:
* **hostname**: The hostname is passed as a tag. By default this will be the value retured by `hostname` on the machine running Telegraf. You can override that value here.
There are 3 configuration options that are configurable per plugin:
* **pass**: An array of strings that is used to filter metrics generated by the current plugin. Each string in the array is tested as a prefix against metrics and if it matches, the metric is emitted.
* **drop**: The inverse of pass, if a metric matches, it is not emitted.
* **interval**: How often to gather this metric. Normal plugins use a single global interval, but if one particular plugin should be run less or more often, you can configure that here.
The way that a plugin emits metrics is by interacting with the Accumulator.
The `Add` function takes 3 arguments:
* **measurement**: A string description of the metric. For instance `bytes_read` or `faults`.
* **value**: A value for the metric. This accepts 5 different types of value:
* **int**: The most common type. All int types are accepted but favor using `int64`
Useful for counters, etc.
* **float**: Favor `float64`, useful for gauges, percentages, etc.
* **bool**: `true` or `false`, useful to indicate the presence of a state. `light_on`, etc.
* **string**: Typically used to indicate a message, or some kind of freeform information.
* **time.Time**: Useful for indicating when a state last occurred, for instance `light_on_since`.
* **tags**: This is a map of strings to strings to describe the where or who about the metric. For instance, the `net` plugin adds a tag named `"interface"` set to the name of the network interface, like `"eth0"`.
The `AddValuesWithTime` allows multiple values for a point to be passed. The values
used are the same type profile as **value** above. The **timestamp** argument
allows a point to be registered as having occurred at an arbitrary time.
Let's say you've written a plugin that emits metrics about processes on the current host.
```go
type Process struct {
CPUTime float64
MemoryBytes int64
PID int
}
func Gather(acc plugins.Accumulator) error {
for _, process := range system.Processes() {
tags := map[string]string {
"pid": fmt.Sprintf("%d", process.Pid),
}
acc.Add("cpu", process.CPUTime, tags)
acc.Add("memoory", process.MemoryBytes, tags)
}
}
```
### Example
```go
// simple.go
import "github.com/influxdb/telegraf/plugins"
type Simple struct {
Ok bool
}
func (s *Simple) Description() string {
return "a demo plugin"
}
func (s *Simple) SampleConfig() string {
return "ok = true # indicate if everything is fine"
}
func (s *Simple) Gather(acc plugins.Accumulator) error {
