recursively retrieve ec2 instance data via http.get
Recursively retrieve EC2 instance data via http.get.
Note: this assumes that a metadata service is available at http://169.254.169.254/. Thus it works on EC2 instances, behavior on other machines is undefined. See the test/ folder for a fake service you can use for testing elsewhere.
npm install ec2-instance-data
var instance = require"ec2-instance-data";instanceinitconsole.log"instance.latest = %s" JSONstringifyinstancelatest null " ";;
Amazon makes available to EC2 instances a variety of instance specific data via http GET calls to a
magic IP address and a set of well-known paths. However the exact data available depends on
what features the instance was started with (e.g. security groups, IAM roles, instance type, etc.),
and Amazon adds more stuff over time, leading to maintenance headaches for any module that tries to wrap
this with an API. This module smooths over that variability by recursively spidering the URLs starting
from a couple common roots:
/latest/dynamic/ (the roots can be overridden
if desired). While it does generate a lot of http requests, it still only takes about 50 milliseconds
to spider the default data set, which should be tolerable when starting a service.
There is another store of meta-data for EC2 instances, tags.
By default all instances created via the console have a
Name tag, but you can add others. The tags for the current instance
can be accessed via the
initTags method, which must be called after
init. This uses EC2's
DescribeTags API via
the AWS SDK for Node.js. Because this is an optional dependency you must explicitly install it with
npm install aws-sdk. To access the tags the client must be initialized with credentials for an account with
permission to use the DescribeTags API, by far the simplest way to do this is to assign an IAM role to the instance,
in which case it will "just work", e.g.
var instance = require"./index.js";instanceinitif errorconsole.logerror;processexit;elseinstanceinitTagsconsole.log;;
"Name": "MyInstanceName""OtherTag": "SomethingElse"
If no IAM Role is available you can set the credentials explicitly before calling
aws-sdk docs for details.