Slow Joe

Simple TCP proxy to test your services for poor network conditions.

Simplicity is the most important aspect. No one wants to spend hours looking for dependencies then learning yet another DSL or quirks of config file, right? Downloading single, static binary (see releases for that) and reading description of few flags is all you need to start. Being docker aficionado makes things even simpler: all burden is to call docker run as service image is available on docker hub.

WARNING: unstable product. API, configuration and behaviour may and will change without a warning.

Quick start

If docker is available it is by far the easiest way to download and run service:

docker run --rm -it adamwasila/slowjoe:latest

INFO[0000] Upstream set                                  address="127.0.0.1:8000"
INFO[0000] Listen on TCP socket                          bind="127.0.0.1:9998"

Otherwise, go to releases subpage and download latest version, unpack and put in your PATH.

Last option is to build on your own. See Install section below for details.

Having binary in PATH you may try following examples. First, run less trivial example where slowjoe works as a proxy to httpbin service. Lets assume that 10% of requests should have throughput limited to 1kb/s.

slowjoe -a -u "httpbin.org:80" -t 0.1 -r 1024

Use curl to check proxy response:

curl http://localhost:9998/headers

{
  "headers": {
    "Accept": "*/*", 
    "Host": "localhost", 
    "User-Agent": "curl/7.64.0"
  }
}

Now hit the following link in you browser http://localhost:9998/image/jpeg and experience modem-like connection speed. Welcome back the Internet of 90s.

Next test closing immediately behaviour:

slowjoe -u "httpbin.org:80" -c 1.0

Now, all requests should be closed without sending any data.

Both behaviours may be mixed together. Here, half of connections are closed immediately and half will be throtled to 1000 bytes per second:

slowjoe -u "httpbin.org:80" -c 0.5 -t 0.5 -r 1000

Finally point your browser to: http://localhost:6000 to see current settings and list of currently opened connections:

Note: -a option must be set to enable web dashboard. Then -p may be used to set port other than default 6000.

Install

Go 1.16+ should be installed in the system. Version 1.16 is minimal to sucessfully compile current codebase.

Download to your GOPATH by typing standard go get command:

go get -u github.com/adamwasila/slowjoe

Alternatively, clone this repository or download latest version. There are no official, versioned releases yet so take latest commit from the master. It opts for go modules thus sources may be put outside GOPATH to compile just fine using regular go build command. If put inside GOPATH remember to refer to documentation of your version of go and set GO111MODULE variable accordingly.

Enter repository and issue command:

go build

Configuration

Help flag -h allows to see full configuration options:

slowjoe -h

Usage of slowjoe:
  -a, --admin                   Enable admin console service
  -p, --admin-port int          Port for admin console service (default 6000)
  -b, --bind string             Address to bind listening socket to (default "0.0.0.0:9998")
  -c, --close-chance float      Probability of closing socket abruptly
  -d, --delay duration          Initial delay when connection starts to deteriorate
  -r, --rate int                Maximum data rate of bytes per second if throttling applied (see --throttle-chance)
  -t, --throttle-chance float   Probability of throttling
  -u, --upstream string         <host>[:port] of upstream service (default "127.0.0.1:8000")
  -v, --verbose                 Enable verbose output (debug logs)
  -w, --very-verbose            Enable very verbose output (trace logs)