havoc

A highly configurable, low footprint reverse proxy for simulating failure between remote systems.

Havoc exposes strategies that allow you to quickly & easily test your applications against remote service failure.

Quick Start

You can download a Linux binary or pull the Docker image and start with the examples below.

Strategies

Strategy	Parameter	JSON Example	Command Line Example	Effect
ReqLimit	Int	"strategy": { "limit": 1000 }	ReqLimit 1000	Accept 1000 requests, then always fail
DropRatio	Float	"strategy": { "drop": 0.05 }	DropRatio 0.05	Fail 5% of requests
Delay	Int	"strategy": { "delay": 1000 }	Delay 1000	Wait 1 second before performing the request
Transparent	n/a	"strategy": { }	n/a	Accept all requests

Examples

REST API Failure

Scenario: drop 50% of requests from my Single Page App (SPA) to my REST API

$ ./havoc solo --url "http://myservice" --strat "DropRatio 0.5" --port 8080

Pointing the SPA to localhost:8080 will fail 50 % of its requests.

Multiple Services & Strategies

Scenario: wrap multiple microservices with different failure strategies

With this settings JSON file:

[
  { "iden": "User", "url": "http://users.system/", "port": 1111, "strategy": { "drop":  0.05 } },
  { "iden": "Sales", "url": "http://sales.system/", "port": 2222, "strategy": {} },
  { "iden": "Marketing", "url": "http://marketing.system/", "port": 3333, "strategy": { "delay": 1000 } },
  { "iden": "Support", "url": "http://support.system/", "port": 4444, "strategy": { "limit": 100 } }
]

we have:

• a proxy for the User service on port 1111 that drops 5% of its requests

• a proxy for the Sales service on port 2222 that is transparent

• a proxy for the Marketing service on port 3333 that delays requests by 1 second

• a proxy for the Support XX service on port 4444 that will accept the first 100 requests the fail

To run:

$ ./havoc farm --file settings.json

Docker Support

There's a docker image at athc/havoc.

You could run the solo example above with:

$ docker run -it -p 8080:8080 athc/havoc solo --url "http://myservice" --strat "DropRatio 0.5" --port 8080

You could run the farm example above with:

$ docker run -v ${PWD}:/havoc-work  --expose=1111-4444:1111-4444 -it havoc farm  --file /havoc-work/settings.json  

Development

To build the project, just clone it then build with Stack:

$ stack install

When the command completes you'll have a havoc binary in the current working directory.

Contributions

Contributions are welcome. Please submit a merge request.

Future Plans

• HTTPS support

• request & response mutators

• TCP/UDP socket support (e.g. proxy a message broker)