Automatic way to pick up the hostname inside docker container - node.js

Question

We're running NodeJS application inside docker container hosted on Amazon EC2 instance. To
To enable Monitoring for Node.js app with Datadog we are using datadog-metrics library and integrate it with our application. We basically require to save the below Javascript code into a file called example_app.js
var metrics = require('datadog-metrics');
metrics.init({ **host: 'myhost', prefix: 'myapp.'** });
function collectMemoryStats() {
var memUsage = process.memoryUsage();
metrics.gauge('memory.rss', memUsage.rss);
metrics.gauge('memory.heapTotal', memUsage.heapTotal);
metrics.gauge('memory.heapUsed', memUsage.heapUsed);
metrics.increment('memory.statsReported');
}
setInterval(collectMemoryStats, 5000);
Although, we are able to successfully publish metrics to datadog but we're wondering if this can be automated. We want build this into our docker image, hence require an automatic way to pick up the hostname, at the very least be able to use the docker hosts name if possible..Because till now we're manually specifying "myhost" and "myapp" values manually. Any better way to fetch the AWS instance hostname value into %myhost?

Answer 1

Why not try?
var os = require(“os”);
var hostname = os.hostname();
It will return the docker container's hostname. If you haven't set a hostname explicitly, using something like docker run -h hostname image command then it will return the docker host's hostname.
Alternatively, you could do this using a deployment tool like puppet, ansible, etc. and template the file when you deploy the container.