metric-log [![Build Status](https://travis-ci.org/CamShaft/metric-log.png?branch=master)](https://travis-ci.org/CamShaft/metric-log)
==========

Log metrics in a simple key=value format for easy parsing.

Install
-------

```sh
npm install --save metric-log
```

API
-----

### metric(measure, value)

```js
var metric = require("metric-log");

metric("request", 1);
  // measure=request val=1
```

### metric(measure, value, units)

```js
var metric = require("metric-log");

metric("response_time", 40, "ms");
  // measure=response_time val=40 units=ms
```

### metric(measure, value, units, obj)

```js
var metric = require("metric-log");

metric("response_time", 40, "ms", {lib:'my-lib'});
  // measure=response_time val=40 units=ms lib=my-lib
```

### metric(obj)

Complex objects can also be passed. Any nested objects/arrays will be converted to JSON.

```js
var metric = require("metric-log");

metric({host: "my.host.com", service: "requests", metric: 5, tags: ["requests", "testing"]});
  // host=my.host.com service=requests metric=5 tags="[\"requests\",\"testing\"]"
```

### metric.context(obj)

You can also setup a default context to be applied to each metric.

```js
var metric = require("metric-log").context({host: "my.host.com"});

metric("response_time", 12, "ms");
  // host=my.host.com measure=response_time val=12 units=ms
```

### metric.context(obj).use(parentContext)

You can also inherit from parent contexts

```js
var express = require("express")
  , metric = require("metric-log")
  , parent = metric.context({host: "my.host.com"});

var app = express();

app.use(function(req, res, next) {
  req.metric = metric.context({request_id: req.get("x-request-id")}).use(parent);
});

app.get("/", function(req, res) {
  req.metric("home_page", 1);
  // host=my.host.com request_id=12345 measure=home_page val=1
});
```

### metric.profile(id[, obj])

Helper function to profile processes like calling an api or database.

```js
var metric = require('metric');

var end = metric.profile('my-api-call');

api('id', function(err, result){
  end();
  // measure=my-api-call val=203 units=ms
});
```

You can also pass some metrics as a second parameter

```js
var end = metric.profile('my-api-call', {at:"info", lib:"my-lib"});

api('id', function(err, result){
  end({err:err});
  // measure=my-api-call val=203 units=ms at=info lib=my-lib err=null
});
```

Tests
-----

```sh
npm test
```

Benchmarks
----------

These were some benchmarks run on my MacBook Pro.

```sh
$ npm run-script bench

․metric(measure, value) 
   201207.24346076458 metrics/sec
․metric(measure, value, units) 
   191791.33103183736 metrics/sec
․metric(obj) 
   267379.67914438504 metrics/sec
․metric(deepObj) 
   136742.78681799537 metrics/sec
․context(measure, value) 
   157629.25598991173 metrics/sec
․context(measure, value, units) 
   143678.16091954024 metrics/sec
․context(obj) 
   156961.2305760477 metrics/sec
․context(deepObj) 
   109613.0658774526 metrics/sec


  9 tests complete (50 seconds)
```