go-ethereum/metrics/README.md

go-metrics
==========

![travis build status](https://travis-ci.org/rcrowley/go-metrics.svg?branch=master)

Go port of Coda Hale's Metrics library: <https://github.com/dropwizard/metrics>.

Documentation: <https://godoc.org/github.com/rcrowley/go-metrics>.

Usage
-----

Create and update metrics:

```go
c := metrics.NewCounter()
metrics.Register("foo", c)
c.Inc(47)

g := metrics.NewGauge()
metrics.Register("bar", g)
g.Update(47)

r := NewRegistry()
g := metrics.NewRegisteredFunctionalGauge("cache-evictions", r, func() int64 { return cache.getEvictionsCount() })

s := metrics.NewExpDecaySample(1028, 0.015) // or metrics.NewUniformSample(1028)
h := metrics.NewHistogram(s)
metrics.Register("baz", h)
h.Update(47)

m := metrics.NewMeter()
metrics.Register("quux", m)
m.Mark(47)

t := metrics.NewTimer()
metrics.Register("bang", t)
t.Time(func() {})
t.Update(47)
```

Register() is not threadsafe. For threadsafe metric registration use
GetOrRegister:

```go
t := metrics.GetOrRegisterTimer("account.create.latency", nil)
t.Time(func() {})
t.Update(47)
```

**NOTE:** Be sure to unregister short-lived meters and timers otherwise they will
leak memory:

```go
// Will call Stop() on the Meter to allow for garbage collection
metrics.Unregister("quux")
// Or similarly for a Timer that embeds a Meter
metrics.Unregister("bang")
```

Periodically log every metric in human-readable form to standard error:

```go
go metrics.Log(metrics.DefaultRegistry, 5 * time.Second, log.New(os.Stderr, "metrics: ", log.Lmicroseconds))
```

Periodically log every metric in slightly-more-parseable form to syslog:

```go
w, _ := syslog.Dial("unixgram", "/dev/log", syslog.LOG_INFO, "metrics")
go metrics.Syslog(metrics.DefaultRegistry, 60e9, w)
```

Periodically emit every metric to Graphite using the [Graphite client](https://github.com/cyberdelia/go-metrics-graphite):

```go

import "github.com/cyberdelia/go-metrics-graphite"

addr, _ := net.ResolveTCPAddr("tcp", "127.0.0.1:2003")
go graphite.Graphite(metrics.DefaultRegistry, 10e9, "metrics", addr)
```

Periodically emit every metric into InfluxDB:

**NOTE:** this has been pulled out of the library due to constant fluctuations
in the InfluxDB API. In fact, all client libraries are on their way out. see
issues [#121](https://github.com/rcrowley/go-metrics/issues/121) and
[#124](https://github.com/rcrowley/go-metrics/issues/124) for progress and details.

```go
import "github.com/vrischmann/go-metrics-influxdb"

go influxdb.InfluxDB(metrics.DefaultRegistry,
  10e9, 
  "127.0.0.1:8086", 
  "database-name", 
  "username", 
  "password"
)
```

Periodically upload every metric to Librato using the [Librato client](https://github.com/mihasya/go-metrics-librato):

**Note**: the client included with this repository under the `librato` package
has been deprecated and moved to the repository linked above.

```go
import "github.com/mihasya/go-metrics-librato"

go librato.Librato(metrics.DefaultRegistry,
    10e9,                  // interval
    "example@example.com", // account owner email address
    "token",               // Librato API token
    "hostname",            // source
    []float64{0.95},       // percentiles to send
    time.Millisecond,      // time unit
)
```

Periodically emit every metric to StatHat:

```go
import "github.com/rcrowley/go-metrics/stathat"

go stathat.Stathat(metrics.DefaultRegistry, 10e9, "example@example.com")
```

Maintain all metrics along with expvars at `/debug/metrics`:

This uses the same mechanism as [the official expvar](https://golang.org/pkg/expvar/)
but exposed under `/debug/metrics`, which shows a json representation of all your usual expvars
as well as all your go-metrics.


```go
import "github.com/rcrowley/go-metrics/exp"

exp.Exp(metrics.DefaultRegistry)
```

Installation
------------

```sh
go get github.com/rcrowley/go-metrics
```

StatHat support additionally requires their Go client:

```sh
go get github.com/stathat/go
```

Publishing Metrics
------------------

Clients are available for the following destinations:

* Librato - https://github.com/mihasya/go-metrics-librato
* Graphite - https://github.com/cyberdelia/go-metrics-graphite
* InfluxDB - https://github.com/vrischmann/go-metrics-influxdb
* Ganglia - https://github.com/appscode/metlia
* Prometheus - https://github.com/deathowl/go-metrics-prometheus
* DataDog - https://github.com/syntaqx/go-metrics-datadog
* SignalFX - https://github.com/pascallouisperez/go-metrics-signalfx