campion

An edge-based circuit breaking middleware

What Does it Do?

Campion is an edge-based serverless framework for implementing circuit-breaking functionality for synchronously called external services. It gives engineers the peace of mind that should their synchronously called services fail, a failure is returned immediately, thereby sheltering their system from cascading failures, giving their failed services time to recover, and providing their end user with a better experience.

Getting Started

Prerequisites

• Either a Cloudflare or an AWS account
• npm installed

Steps

1. Run npm install campion -g to install.
2. Type campion or campionaws to use.

Cloud Providers

Provider	Trade-offs
Cloudflare	Cloudflare Workers is an incredible platform. When a user deploys Campion on Workers, it deploys and functions almost instantly. In our tests, it proved to be faster than the Amazon offering, both in initial setup and with throughput on requests. On average, Workers was 28% faster than Lambda@Edge from an end-user perspective when processing a request and returning a response
AWS	For those who already have an AWS account, Lambda@Edge is a great option. The biggest thing to be aware of here is that AWS’s CDN takes longer to replicate than Cloudflare’s does. What this means is that deploying Campion on AWS can take up to thirty minutes before the code rolls out to all the servers on the CDN. Similarly, deleting Campion from Lambda@Edge can take several hours. Of course, once it’s deployed, Campion works great on Lambda@Edge. It's also worth mentioning that AWS imposes a limit of 53.2 KB of data that can be transferred

Commands

Start every command with campion <commandName>, to use Campion with Cloudflare, and campionaws <commandName>, to use Campion with AWS. For example, campion setup or campionaws stats.

Command	Action
setup	Sets up Campion and deploys all necessary code to the cloud provider of your choice. In AWS this can take up to 30 minutes
add	Adds a service to be protected by Campion
update	Updates any service you have with new configuration
delete	Deletes any service
flip	Flips the circuit state to any state of your choosing
list	Lists all of your currently protected services
stats	Launches a browser window at localhost:7777 with your metrics and services configuration
wipe	Wipes Campion completely from your cloud provider. Within Cloudflare, the entire wiping happens in a matter of seconds. In AWS, however, it can take up to a few hours given that AWS requires that the circuit breaker code be completely removed from the Cloudfront distribution (this is how Campion is able to be distributed to the edge). If you have Campion deployed on AWS, you're able to run the wipe command as often as you'd like to check if Campion has finished wiping

Service Configuration

Property	Definition
Service url	The public url to the service that you're trying to call
Service name	The public url to the service that you're trying to call
Max latency	The amount of time in milliseconds that Campion should wait until the request is considered to have failed
Timespan	The timespan in milliseconds that Campion should consider when calculating the number of failed requests in order deem a service to be down and flip the circuit OPEN
Network failures	The number of network failures (within timespan) that will flip the circuit OPEN
Service failures	The number of service failures, 500-level responses, (within timespan) that will flip the circuit OPEN
Error timeout	The amount of time in milliseconds that Campion should wait before fliping the circuit from OPEN to HALF-OPEN
Percent of requests	The percent of requests that Campion should allow to hit the protected service when attempting to switch from HALF-OPEN to CLOSED
Success threshold	The number of successfull requests (within timespan) that will flip the circuit from HALF-OPEN to CLOSED

Circuit State

State	Definition
CLOSED	All traffic is allowed to hit the service
OPEN	No traffic is allowed to hit the service. The service has failed, either because it has reached its network failure or service failure count
HALF-OPEN	Only a portion of the traffic is allowed to attempt to hit the service as an auto-recovery measure
FORCED-OPEN	This is a developer testing tool that will block all traffic to the service indefinitely until the breaker is flipped back manually

Metrics

Campion comes with a beautiful seamlessly integrated metrics UI. To see how your services are performing, what the traffic looks like, what the current services and their configurations look like, and when and how the state of your circuits changed, simply type campion stats for Cloudflare, or campionaws stats for AWS, from your CLI.

The Team

Gabriel De Almeida Software Engineer West Palm Beach, FL

Arthur Kauffman Software Engineer New York, NY

Ben Zelinski Software Engineer Cleveland, OH