checkUrl

Author: Ciaran Finnegan Version: 0.0.1

description

Node.js Lambda function that tests the availability of a web URL. Targets are specified in a json object passed to the event handler, urlChecker.checkUrl

In AWS Lambda console set handler to urlChecker.checkUrl and configure a Cloudwatch event trigger to supply a json object specifying the URLs to be checked on a schedule e.g.

{ "My google test URL": "http://google.com", "My glimps test URL": "http://glimps.in", "My test URL that will fail" : "http://google.com/xyz" }

• Pass if a 2xx code is returned by a url (http or https).
• Fail on any other error (e.g. URL not found or other http error code)*/

Implementation Notes

• You will aslo need to configure a role with required access to write to cloudwatch, see this URL https://docs.aws.amazon.com/lambda/latest/dg/monitoring-functions.html
• If you wish to test hosts inside a VPC there are further configuration steps, see this URL https://docs.aws.amazon.com/lambda/latest/dg/vpc.html
• The Lambda function will need to access Cloudwatch endpoints for your region to push logs and metrics, see this URL https://docs.aws.amazon.com/general/latest/gr/rande.html (if direct connectivity is not available a web proxy can be passed, see #32 in urlChecker.js, this functionality has not been tested)

Sample Error Codes

• SUCCESS :: Received HTTP Response from http://aws.amazon.com/ with Status Code :: 200
• FAIL :: Received HTTP Response from http://aws.amazon.com/nnn with Status Code :: 404
• FAIL :: Error trying to connect to http://aws.amazon.comnnn, Error Code is :: ENOTFOUND

Installation

• Create a new Security Group

• • Name, urlChecker-out, Description urlChecker
• • Inbound rules none
• • Outbound rules, Protocol: TCP Ports: 0 - 65535 Destination: 0.0.0.0/0, Protocol DNS: Port: 53 Destination 0.0.0.0/0 (adjust as required)

• Create IAM Role

• • Name, Lambda-urlChecker

• Create a new lambda function called urlChecker

• • Description 'Checks URLs and logs to Cloudwatch'
• • Code entry type, zip file
• • Runtime, Node.js 8.10
• • Configure test events, checkURL , example below, replace with accessible test URL { "proxy-reports": "http://10.180.64.254/squid-reports/", "SOP": "http://oilssolapp01.sydapp.net:8000/sap/public/ping?sap-client=001" }
• • Handler, urlChecker.checkURL
• • Memory 128MB
• • Timeout, 2 minutes (adjust as required)
• • Execution Role, Lambda-urlChecker
• • Network, choose applicable VPC
• • Subnets, choose applicable subnets
• • Security Groups, (urlChecker) | urlChecker-out
• • Concurrency, use unreserved amount

• Create Cloudwatch Rule

• • Fixed rate of 5 minutes
• • Add Target, Lambda function, urlCheck
• • Configure input, Constant (JSON text) e.g. { "kanyini": "http://kanyini.io", "glimps": "http://glimps.in", "bedandbarns": "http://www.bedandbarns.com"}
• • Configure Dashboard
• • • to be completed
• • Configure Alarms
• • • e.g. UrlNotResponding >= 1 for 2 datapoints within 10 minutes
• • • to be completed

Enhancements

Update to pass configuration parameters for each URL e.g.

{ "url": "http://aws.amazon.com, "method": "GET", "timeout": 2000, "followRedirect": true, "maxRedirects": 5 }

Pass proxy configuration as a parameter

Also, test that this works

Automate creation of dashboards & alerts