cwg: The CloudWatch gateway for custom metrics

Install on your instances

• Spin up instaces with an instance role that grants access to: cloudwatch:PutMetricData
• Install Python (it might already be installed)
• Install aws-cli
• Download the latest cloudwatch-gateway release archive
• As root:
  • tar xvzPf cloudwatch-gateway-*tgz
  • /opt/bin/github.com/kfeldmann/cloudwatch-gateway/bin/setup.sh <region> <appname> <environment> <tier> (substitute your particulars for the four arguments)
• Take a look at the monitors in cloudwatch-gateway/monitors/<OS>/enabled
• To disable any monitors, jut move them outside of the enabled directory (the disabled directory is a convenient place to store unused monitors)
• To add custom monitors of your own, just move (or link) them into the enabled directory. Monitors installed in this way can be written in any language, and should simply print their metrics to stdout (see details below).

Reap the benefits

• The metrics will be written to CloudWatch under the namespace <appname>-<environment>-<tier>
• The metrics will aslo be written to syslog with tag cwg, and priority local1.info

Publish your own custom metrics

Once CloudWatch Gateway's daemon (cwg) is running, you can easily send your own custom metrics to CloudWatch, either directly from your application or from a script or helper app.

First take a look at the units that CloudWatch supports and choose the appropriate one for your metric.

Create a script (in any language) to measure your metric value(s). Then simply add that script to the cloudwatch-gateway/monitors/<OS>/enabled directory. The script should run once (not loop) and write its metrics to stdout. The run-monitors cron job will run your custom monitor script every minute and pipe the output to the cloudwatch-gateway.

The format of the metrics to be fed to cwg is:

<MetricName> <NumericValue> <Unit>

Multiple metrics can be sent at once, as long as they are separated by newlines.

Example:

#!/bin/sh
A=$(/bin/grep MemAvailable /proc/meminfo | /bin/awk '{print $2}')
T=$(/bin/grep MemTotal /proc/meminfo | /bin/awk '{print $2}')
AP=$(/bin/echo "scale=1; 100-(${A}*100)/${T}" | /usr/bin/bc)
/bin/echo "MemUsagePct ${AP} Percent"

It's as easy as that!

Take a look at the included monitors for (a couple) more examples.