Fakettp

Fakettp is an http debugging proxy allowing you to easily black box test how an application reacts when services it relies upon act differently than expected. Fakettp allows you to control the following as you test at the black box level:

• response code
• response time
• response headers
• response body
• control over which endpoints proxy though and which are hijacked

You can set global responses, or you can pass in individual endpoints where those responses apply, and proxy all other endpoint requests to the original service. This gives you the ability to test your system against the other service and simulate an error on a single endpoint while the rest of the service works normally.

Use Case

What inspired this repo!: We had Service A calling Service B's endpoints internally. We needed some of the endpoints in Service B to do their job, while for one of them we needed to verify how Service A behaved when Service B returned different content and status codes. After using this tool, our QA was able to verify all the edge-cases with which they were interested!

Sample Usage

From the source or compiled binary, just set the response you want. Note that you can pass in multiple headers to be returned by using -header repeatedly. You can also limit which methods the hyjacking will affect with multiple -method parameters. You can also choose to match against a pattern string if you additionally pass in the -pattern_match flag.

Hyjac a single endpoint and proxy all other calls:

go run main.go -proxy_host http://example.com -proxy_port 9092 -hyjack /api/user -port 5555 -code 418 -body "I'm a teapot"

We can also use a config file instead (more on this below!) and override proxy settings with flags (or add an additional hyjacked route):

go run main.go -config my.conf -proxy_delay 5s

We can match against regular expressions / patterns:

$ go run main.go -port 5555 -code 201 -header POST -pattern_match -hyjack '\/api\/users\/[0-9]+\/credits.json'

Return the same data for all calls to this service:

$ go run main.go -port 5555 -code 201 -header 'Content-Type: application/json' -header 'Cache-Control: max-age=3600' -body '{"json":true} -method POST -method GET'

The above setup would result in the following response from any path on localhost:5555:

$ curl -v localhost:5555/foo/bar/raz -d '{"foo":"bar"}'
*   Trying 127.0.0.1...
* Connected to localhost (127.0.0.1) port 5555 (#0)
> POST /foo/bar/raz HTTP/1.1
> Host: localhost:5555
> User-Agent: curl/7.43.0
> Accept: */*
> Content-Length: 13
> Content-Type: application/x-www-form-urlencoded
>
* upload completely sent off: 13 out of 13 bytes
< HTTP/1.1 201 Created
< Cache-Control: max-age=3600
< Content-Type: application/json
< Date: Wed, 02 Sep 2015 16:17:48 GMT
< Content-Length: 13
<
* Connection #0 to host localhost left intact
{"json":true}

Config File

When passing command line flags, you are limited to either hyjacking all requests or only requests to a single endpoint. With a config file, you can specify multiple routes to behave differently. Note: config values are overridden by command line flags in the case of proxy_host, proxy_port, and port. For all other values, they add an additional fake for hyjacking.

Sample Config:

{
    "proxy_host": "http://0.0.0.0",
    "proxy_port": 9092,
    "proxy_delay": "2s",
    "port": 5000,
    "fakes": [
        {
            "hyjack": "/api/settings.json",
            "code": 500
        },
        {
            "hyjack": "/api/users.json",
            "methods": [
                "GET",
                "POST"
            ],
            "body": "{\"json\":true}",
            "code": 201,
            "headers": [
                "Content-Type: application/json",
                "Cache-Control: max-age=3600"
            ],
            "time": "1m3s15ms"
        },
        {
            "hyjack": "\/api\/users\/[0-9]+\/credits.json",
            "code": 404,
            "pattern_match": true
        },
    ]
}

Sample Logs

Logs show the requested URI, if the request was hyjacked or proxied, and shows a request id at the beginning of log lines dealing with a request.

2015/09/02 14:10:22 starting on port :5555
[1dfc34e] 2015/09/02 14:10:23 new request /api/user/get.json
[1dfc34e] 2015/09/02 14:10:23 proxying request
[4666fb4] 2015/09/02 14:10:36 new request /api/functions.json
[4666fb4] 2015/09/02 14:10:36 hyjacking route /api/functions.json (10ms)
[4666fb4] 2015/09/02 14:10:36 setting header Content-Type:application/json
[4666fb4] 2015/09/02 14:10:36 setting header Cache-Control:max-age=3600

Tests

You can run tests like normal with $ go test, however, you can make the tests show application level logging with $ go test -show_logs. Tests make use of ports 4333 and 4332 and require these ports to be available.