Christian Bongiorno Christian Bongiorno - 10 days ago 6
Node.js Question

How to publish FROM an AWS lambda to a cloud watch metric in Node.js

Inside a lambda I use to periodically check in on a service I check the value of the result from the server and I want that value published to AWS cloudwatch as a metric to form a linechart.

I can't for the life of me figure our how this is done. 2 hours combing around the AWS docs leads nowhere.Is this even possible?

To be clear this isn't a metric ABOUT a lambda, it's a metric published FROM the lamdba.

Code:

'use strict';

const https = require('http');


exports.handler = (event, context, callback) => {
const now = new Date()
const yesterday = new Date(now.toISOString())
yesterday.setTime(now.getTime() - (1000 * 60 * 60 * 24)); // 1 day ago)

const params = [
['limit',0],
['pageStart',0],
['startsOnOrAfter',encodeURIComponent(yesterday.toISOString())],
['startsOnOrBefore',encodeURIComponent(now.toISOString())]
].map(kv => `${kv[0]}=${kv[1]}&`).reduce((s1,s2) => s1.concat(s2))

var uri = `http://service/query?${params}`
const req = https.request(uri, (res) => {
let body = '';
res.setEncoding('utf8');
res.on('data', (chunk) => body += chunk);
res.on('end', () => {
if (!res.headers[ 'content-type' ].match('application/.*?json')) {
return callback(`unknown content type ${res.headers[ 'content-type' ]}`,body)
}
body = JSON.parse(body);
if(body.total && body.total > 0) {
callback(null, body.total); // body.total to form a line chart
}
else {
callback({
message: 'No plans found for time period',
uri: uri
})
}
});
});
req.on('error', callback);
req.end();
};

Answer

Yes, that is possible:

const AWS = require('aws-sdk');

const metric = {
  MetricData: [ /* required */
    {
      MetricName: 'YOUR_METRIC_NAME', /* required */
      Dimensions: [
        {
          Name: 'URL', /* required */
          Value: url /* required */
        },
      /* more items */
      ],
      Timestamp: new Date(),
      Unit: 'Count',
      Value: SOME_VALUE
    },
    /* more items */
  ],
  Namespace: 'YOUR_METRIC_NAMESPACE' /* required */
};

const cloudwatch = new AWS.CloudWatch({region: 'eu-west-1'});
cloudwatch.putMetricData(metric, (err, data) => {


if (err) {
    console.log(err, err.stack); // an error occurred
  } else {
    console.log(data);           // successful response
}
});

First your create the data that you want to store as a metric, the you use the CloudWatch API to send it to CloudWatch. (Of course the function must have permission to write to CloudWatch.)

More documentation is here: https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/CloudWatch.html

Comments