Helloer, a tiny workload to test your cloud connectivity

Motivation

When it comes to the digital transformation projects and more specifically when dealing with large Move to Cloud projects, you’ll often end up with a (customer driven) complex hybrid architecture.

In this context you’ll be required to validate the LZ design, and in most cases, the emphasis will be on the network & connectivity aspects.

To test the connectivity and eventually deliver a POC, a Study or a to validate a design update, you’ll need a pair of workloads that can work together to validate the traffic connectivity.

The Helloer is designed to fulfill this role.

It is a tiny HTTP backend that can be deployed on almost any type of compute infrastructure (Kubernetes, Functions, App Services, even VMs ) , that responds to simple HTTP requests that can be resolved locally or forwarded to another endpoint in order to test transitive connectivity use cases.

In order to generate traffic on the Helloer, you can use it’s companion app the Greeter, that will address HTTP requests to the Helloer backend.

Features

The following diagram illustrates a usage of the Helloer for poc-ing the network and security aspects of an Azure ESLZ design, however it can be accomadated for pretty much any Cloud :

Public Ingress Connectivity

In this use case you'd like to deploy the workload on it's hosting infrastructure and to call it from a certain place of your cloud architecture, or even test public ingress connectivity to your workload.

In order to do that you can simply hit the '/connectivity/local' endpoint of the workload and get yourself a short response JSON payload.

Public Egress Connectivity

In this use case you'd like to deploy the workload on it's hosting infrastructure and to make sure it has connectivity to external, publicly hosted SaaS solutions.

In order to do that you can simply hit the '/connectivity/public' endpoint of the workload which will in turn call the Github API to list the repos of a given user. It is a conveniant way for testing the egress public connectivity and can be also used to highlight all the security (NAT, FW) that will be applied on such workloads.

Private Spoke Connectivity

In this use case you'd like to deploy the workload on it's hosting infrastructure and to make sure it has connectivity to other LZs in your cloud scope. In Azure it would bind to the notion of "spoke" , and you would usually need to traverse the Hub part ( mainly the Connectivity subscription of the Azure ESLZ).

In order to do that you can simply hit the '/connectivity/spoke' endpoint of the workload which will in turn call another Helloer or any other http level server placed in another spoke. You can override the transitive url via an evnronnement property.

Private On Prem Connectivity

In this use case you'd like to deploy the workload on it's hosting infrastructure and to make sure it has connectivity to your on premises workloads. In this case you're going to be testing the transversal of private hybrid connectivity trunks ( such as Azure Express route) and also the security enforcements on this path ( usually traversing the Azure HUB Connetivity ESLZ subscription).

In order to do that you can simply hit the '/connectivity/onprem' endpoint of the workload which will in turn call another Helloer or any other http level server placed in another spoke. You can override the transitive url via an evnronnement property. You can also extend and override the current handler to write something more complex then a simple HTTP hit.

Health Probes

In this use case you'd like to deploy the workload on an infrastructure that lives behind a Load Balancer. It can be Kubernetes, VM Sets or any other scale-out technology.

Most of the available infrastructures will require healthchecks, being it on the Kub level or simply as a backend probe for most of the LBs ( think backend health on Azure App Gateways).

In order to integrate with those infrastructures you can use the '/health' endpoint of the workload that will return a small payload with a 200 HTTP status, which is more then sufficient to deploy the workload in those conditions

Performance Tracking

The application integrates very basic perfromance tracking that simply exposes the aggregated RPS (request per second) metric. It can come handy in order to check quota limits or basic network connectivity performance, usefull when benching different Load Balancer solutions.

Code

The code is pretty staightfoward and easy to update :

• app/app.js is the main application entry point
• http handlers are stored under the app/handlers directory
• utility modules (logger, response builder) are stored under the app/util directory
• unitary tests are stored in the test/ directory and define a simple yet usefull test harness for internal utility modules

A simple Docker file, located in the root folder, is used for packaging the Helloer as a container so you can to host it on any kind of cloud infra.

Usage

Configuration

The overall configuration is performed via environnement variables in order to fit with the container deployement model.

The following table lists the used environnement variables :

Env Var Name	Default Value	Purpose
HELLOER_PORT	8080	The http port to serve
HELLOER_BACKEND_TYPE	helloer	The type of the backend, will determine the log filename and appear in the reponse payload
HELLOER_BACKEND_ID	generated UUID	The id of the backend, will appear in the reponse payload
HELLOER_FORWARDER_GITHUB_USERNAME	funkomatic	Used as github user to list it's public repos, SaaS test
HELLOER_FORWARD_PRIVATE_URL	http://localhost:8080/connectity/private	URL to hit to test spoke to spoke connectivity, change the value to fit the deployed helloer in another spoke
HELLOER_FORWARD_ONPREM_URL	http://my.host.is:9086/whatever	Used for onprem test, obvioulsy you'll have to override that one with a valid url exposed on prem

HTTP Endpoints

Endpoint	Usage
/health	health probe for containerized infra, returns HTTP code 200 if running
/connectivity/local	helloer responder, simply says hello
/connectivity/public	translates calls to github api
/connectivity/spoke	translates calls to other spoke http server (you can use a dedicated helloer as well)
/connectivity/onprem	translates calls to on prem http server (uou can use a dedicated helloer as well)
/perfs	exposition of basic aggregated Request Per Second metric as well as breakdown per service

HTTP Responses

Common Reponse Payload

All response payloads will contain at least the identification of the backend, and some usefull infromation on the request, handy to track your flows when traversing NATs, LBs :

{
  "backend_type": "helloer",
  "backend_id": "helloer-6d8a3c0a-fcdd-465e-a980-48f5e3462833",
  "request_source_ip": "::ffff:127.0.0.1",
  "response_id": "8843d16f-775c-4332-a911-4ccf37a11252",
  "response_date": "2022-02-10T10:43:47.534Z"
}

The 'response_id' and 'response_date' fields will be re-generated for each request, helping to track the responses behind routing/redirection services.

Specific Reponse Payloads

When the workload will reach for an external system (spoke, saas solution, onprem), the payload will be extended with attributes named <connectivity.type_status> , providing the status of the bounced call and <connectivity.type_response> providing the payload response from the external system.

For instance, when addressing another spoke helloer, the payload will look similar to the following :

{
  "backend_type": "helloer",
  "backend_id": "helloer-6d8a3c0a-fcdd-465e-a980-48f5e3462833",
  "request_source_ip": "::ffff:127.0.0.1",
  "response_id": "d85ea02c-5a84-4d00-897b-1ec5d3f1041d",
  "response_date": "2022-02-10T10:42:50.164Z",
  "spoke_status": "success",
  "spoke_response": {
    "backend_type": "spoker",
    "backend_id": "spoker-2ffcb186-5e9c-4431-9d4a-9157304fe2f1",
    "request_source_ip": "::ffff:127.0.0.1",
    "response_id": "17adc02c-6722-413e-bcda-9e56e7a80cb2",
    "response_date": "2022-02-10T10:42:50.168Z",
    "message": "hello"
  }
}

Starting the app

Clone the repo, eventually override the environnement variables then perform the following commands :

npm run app:clean
npm run app:init
npm run app:start

And expect an output silmilar to the following :

> helloer@1.0.1 app:start
> node app.js

2022-02-24 09:38:29-99 [info] (helloer) starting backend
2022-02-24 09:38:30-00 [info] (helloer) backend started, listening on port=8080

Note the (helloer) tag that is defined by the HELLOER_BACKEND_TYPE environnement variable.

A start.sh script is also provided and is intended to run the app on a Linux VMs in detached mode using the following cmd line :

nohup ./start.sh &

Logs

The application will produce a log file which naming depends on the value of the HELLOER_BACKEND_TYPE environnement variable, the log file pattern being HELLOER_BACKEND_TYPE.log.

example :

export HELLOER_BACKEND_TYPE=webapp1
npm run app:start

ls *.log
webapp1.log

Packaging

Generate binary package

You can build a binary package ready to run using the following commands :

npm run app:clean
npm run app:init
npm run app:package

This sequence will create an archive named helloer-dist-vMAJ.vMIN.vREL.tgz to be used on any VM provided you already have a node/npm installation.

For version 1.0.3 , you'll see the following file created :

helloer-dist-1.0.3.tgz

Use docker image

For containerized deployements you can use the image available on the Docker Hub. It is updated by the Github CI/CD worklow on each code change.

In order to get the container simply issue the following command :

docker pull zlatkoa/helloer:1.0.3

You can also build your own image using the provided Dockerfile by issuing, for instance :

npm run app:dockerize