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StatsD backend for AWS CloudWatch

Overview

StatsD is a smart Node.js package that collects and aggregates statistics from differents apps sent over the UDP protocol. At a set time interval it forwards the aggregated data to a configured backend. It is pluggable with several backends available, the most popular being Graphite, a python/django monitoring tool.

With aws-cloudwatch-statsd-backend you can replace Graphite in favour of AWS Cloudwatch for your monitoring purposes, appropriate for sites on the Amazon EC2 cloud.

Counters, timers, gauges and sets are all supported.

Installation

You need node.js installed on your system aswell as StatsD. Follow the instructions on their sites or see this blog post/tutorial on how to install these components on a Windows system.

The CloudWatch backend is an npm package that can be installed with the npm command which comes with your installation of node.js. Go to the npm site for more information.

npm install aws-cloudwatch-statsd-backend

The package has two depdencies that should be installed automatically, awssum and fmt. Awssum is a node.js package encapsulating the AWS API.

Configuration

The StatsD and its backends are configured in a json object placed in a file supplied to StatsD at the command line. For example, start StatsD with the following.

node ./stats.js ./myConfig.js

The following demonstrates the minimum config for the CloudWatch backend.

{
    backends: [ "aws-cloudwatch-statsd-backend" ],
    cloudwatch: 
    {
        accessKeyId: 'YOUR_ACCESS_KEY_ID', 
        secretAccessKey:'YOUR_SECRET_ACCESS_KEY', 
        region:"YOUR_REGION"
    }
}

The access keys can be you personal credentials to AWS but it is highly recommended to create an ad hoc user via Amazon's IAM service and use those credentials.

The region is for example EU_WEST_1 or US_EAST_1.

The above will create a metric with the default namespace, AwsCloudWatchStatsdBackend, and send an http request to CloudWatch via awssum.

See the CloudWatch documentation for more information on these concepts.

The metric name, unit and value depends on what you send StatsD with your UDP request. For example, given

gorets:1|c

the Unit will be Counter, the metric name gorets. The value will be the aggregated count as calculated by StatsD.

ms corresponds the unit Milliseconds. *s and g to None.

Warning Indescriminate use of CloudWatch metrics can quickly become costly. Amazon charges 50 cents for each combination of namepace, metric name and dimension per month. However, the 10 first per month are free.

Additional configuration options

The cloudwatch backend provides ways to override the name and namespace by cofiguration. It can also capture these components from the bucket name.

The following overrides the default and any provided namespace or metric name with the specified.

{
    backends: [ "aws-cloudwatch-statsd-backend" ],
    cloudwatch: 
    {
        accessKeyId: 'YOUR_ACCESS_KEY_ID', 
        secretAccessKey: 'YOUR_SECRET_ACCESS_KEY', 
        region: 'YOUR_REGION',
        namespace: 'App/Controller/Action', 
        metricName: 'Request',
        dimensions: [
            { Name: "dim1", Value: "val1" },
            { Name: "dim2", Value: "val2" }
        ]
    }
}

Using the option processKeyForNamespace (default is false) you can parse the bucket name for namespace in addition to metric name. The backend will use the last component of a bucket name comprised of slash (/), dot (.) or dash (-) separated parts as the metric name. The remaining leading parts will be used as namespace. Separators will be replaced with slashes (/).

{
    backends: [ "aws-cloudwatch-statsd-backend" ],
    cloudwatch: 
    {
        accessKeyId: 'YOUR_ACCESS_KEY_ID', 
        secretAccessKey: 'YOUR_SECRET_ACCESS_KEY', 
        region: 'YOUR_REGION',
        processKeyForNamespace:true
    }
}

For example, sending StatsD the following

App.Controller.Action.Request:1|c

is will produce the equivalent to the former configuration example. Note that both will be suppressed if overriden as in the former configuration example.

Dimensions can be specified in the statistic name, using a special __name_value syntaxis. For instance:

App.Controller.Action.__HostName_server1:1|c

Will set the "HostName" dimension to the value "server1".

If a string is provided to the processKeyForNamespace option (instead of the boolean true), that string will be used as a regular expression for splitting the stat name in namespace/dimension components (instead of the default '[.-/]').

Tutorial

This project was launched with a following blog post/tutorial describing the implementation chain from log4net to Cloudwatch on a Windows system.

Also in the series:

Improving the CloudWatch Appender

A CloudWatch Appender for log4net

endorse