Toxiproxy

Toxiproxy is a framework for simulating network conditions. It's made specifically to work in testing, CI and development environments, supporting deterministic tampering with connections, but with support for randomized chaos and customization. Toxiproxy is the tool you need to prove with tests that your application doesn't have single points of failure. We've been successfully using it in all development and test environments at Shopify since October, 2014. See our [blog post][blog] on resiliency for more information.

Toxiproxy usage consists of two parts. A TCP proxy written in Go (what this repository contains) and a client communicating with the proxy over HTTP. You configure your application to make all test connections go through Toxiproxy and can then manipulate their health via HTTP. See Usage below on how to set up your project.

For example, to add 1000ms of latency to the response of MySQL from the Ruby client:

Toxiproxy[:mysql_master].downstream(:latency, latency: 1000).apply do
  Shop.first # this takes at least 1s
end

To take down all Redis instances:

Toxiproxy[/redis/].down do
  Shop.first # this will throw an exception
end

While the examples in this README are currently in Ruby, there's nothing stopping you from creating a client in any other language (see Clients).

Table of Contents

• Toxiproxy
• Table of Contents
• Why yet another chaotic TCP proxy?
• Clients
• Example
• Usage
  • 1. Installing Toxiproxy
  • Upgrading from Toxiproxy 1.x
  • 2. Populating Toxiproxy
  • 3. Using Toxiproxy
  • 4. Logging
  • Toxics
  • latency
  • down
  • bandwidth
  • slow_close
  • timeout
  • reset_peer
  • slicer
  • limit_data
  • HTTP API
  • Proxy fields:
  • Toxic fields:
  • Endpoints
  • Populating Proxies
  • CLI Example
  • Metrics
  • Frequently Asked Questions
  • Development
  • Release

Why yet another chaotic TCP proxy?

The existing ones we found didn't provide the kind of dynamic API we needed for integration and unit testing. Linux tools like nc and so on are not cross-platform and require root, which makes them problematic in test, development and CI environments.

Clients

• toxiproxy-ruby
• toxiproxy-go
• toxiproxy-python
• toxiproxy.net
• toxiproxy-php-client
• toxiproxy-node-client
• toxiproxy-java
• toxiproxy-haskell
• toxiproxy-rust
• toxiproxy-elixir

Example

Let's walk through an example with a Rails application. Note that Toxiproxy is in no way tied to Ruby, it's just been our first use case. You can see the full example at sirupsen/toxiproxy-rails-example. To get started right away, jump down to Usage.

For our popular blog, for some reason we're storing the tags for our posts in Redis and the posts themselves in MySQL. We might have a Post class that includes some methods to manipulate tags in a Redis set:

class Post < ActiveRecord::Base
  # Return an Array of all the tags.
  def tags
    TagRedis.smembers(tag_key)
  end

  # Add a tag to the post.
  def add_tag(tag)
    TagRedis.sadd(tag_key, tag)
  end

  # Remove a tag from the post.
  def remove_tag(tag)
    TagRedis.srem(tag_key, tag)
  end

  # Return the key in Redis for the set of tags for the post.
  def tag_key
    "post:tags:#{self.id}"
  end
end

We've decided that erroring while writing to the tag data store (adding/removing) is OK. However, if the tag data store is down, we should be able to see the post with no tags. We could simply rescue the Redis::CannotConnectError around the SMEMBERS Redis call in the tags method. Let's use Toxiproxy to test that.

Since we've already installed Toxiproxy and it's running on our machine, we can skip to step 2. This is where we need to make sure Toxiproxy has a mapping for Redis tags. To config/boot.rb (before any connection is made) we add:

require 'toxiproxy'

Toxiproxy.populate([
  {
    name: "toxiproxy_test_redis_tags",
    listen: "127.0.0.1:22222",
    upstream: "127.0.0.1:6379"
  }
])

Then in config/environments/test.rb we set the TagRedis to be a Redis client that connects to Redis through Toxiproxy by adding this line:

TagRedis = Redis.new(port: 22222)

All calls in the test environment now go through Toxiproxy. That means we can add a unit test where we simulate a failure:

test "should return empty array when tag redis is down when listing tags" do
  @post.add_tag "mammals"

  # Take down all Redises in Toxiproxy
  Toxiproxy[/redis/].down do
    assert_equal [], @post.tags
  end
end

The test fails with Redis::CannotConnectError. Perfect! Toxiproxy took down the Redis successfully for the duration of the closure. Let's fix the tags method to be resilient:

def tags
  TagRedis.smembers(tag_key)
rescue Redis::CannotConnectError
  []
end

The tests pass! We now have a unit test that proves fetching the tags when Redis is down returns an empty array, instead of throwing an exception. For full coverage you should also write an integration test that wraps fetching the entire blog post page when Redis is down.

Full example application is at sirupsen/toxiproxy-rails-example.

Usage

Configuring a project to use Toxiproxy consists of three steps:

1. Installing Toxiproxy
2. Populating Toxiproxy
3. Using Toxiproxy

1. Installing Toxiproxy

Linux

See Releases for the latest binaries and system packages for your architecture.

Ubuntu

$ wget -O toxiproxy-2.1.4.deb https://github.com/Shopify/toxiproxy/releases/download/v2.1.4/toxiproxy_2.1.4_amd64.deb
$ sudo dpkg -i toxiproxy-2.1.4.deb
$ sudo service toxiproxy start

OS X

With Homebrew:

$ brew tap shopify/shopify
$ brew install toxiproxy

Or with MacPorts:

$ port install toxiproxy

Windows

Toxiproxy for Windows is available for download at https://github.com/Shopify/toxiproxy/releases/download/v2.1.4/toxiproxy-server-windows-amd64.exe

Docker

Toxiproxy is available on Github container registry. Old versions <= 2.1.4 are available on on Docker Hub.

$ docker pull ghcr.io/shopify/toxiproxy
$ docker run --rm -it ghcr.io/shopify/toxiproxy

If using Toxiproxy from the host rather than other containers, enable host networking with --net=host.

$ docker run --rm --entrypoint="/toxiproxy-cli" -it ghcr.io/shopify/toxiproxy list

Source

If you have Go installed, you can build Toxiproxy from source using the make file:

$ make build
$ ./toxiproxy-server

Upgrading from Toxiproxy 1.x

In Toxiproxy 2.0 several changes were made to the API that make it incompatible with version 1.x. In order to use version 2.x of the Toxiproxy server, you will need to make sure your client library supports the same version. You can check which version of Toxiproxy you are running by looking at the /version endpoint.

See the documentation for your client library for specific library changes. Detailed changes for the Toxiproxy server can been found in CHANGELOG.md.

2. Populating Toxiproxy

When your application boots, it needs to make sure that Toxiproxy knows which endpoints to proxy where. The main parameters are: name, address for Toxiproxy to listen on and the address of the upstream.

Some client libraries have helpers for this task, which is essentially just making sure each proxy in a list is created. Example from the Ruby client:

# Make sure `shopify_test_redis_master` and `shopify_test_mysql_master` are
# present in Toxiproxy
Toxiproxy.populate([
  {
    name: "shopify_test_redis_master",
    listen: "127.0.0.1:22220",
    upstream: "127.0.0.1:6379"
  },
  {
    name: "shopify_test_mysql_master",
    listen: "127.0.0.1:24220",
    upstream: "127.0.0.1:3306"
  }
])

This code needs to run as early in boot as possible, before any code establishes a connection through Toxiproxy. Please check your client library for documentation on the population helpers.

Alternatively use the CLI to create proxies, e.g.:

toxiproxy-cli create -l localhost:26379 -u localhost:6379 shopify_test_redis_master

We recommend a naming such as the above: <app>_<env>_<data store>_<shard>. This makes sure there are no clashes between applications using the same Toxiproxy.

For large application we recommend storing the Toxiproxy configurations in a separate configuration file. We use config/toxiproxy.json. This file can be passed to the server using the -config option, or loaded by the application to use with the populate function.

An example config/toxiproxy.json:

[
  {
    "name": "web_dev_frontend_1",
    "listen": "[::]:18080",
    "upstream": "webapp.domain:8080",
    "enabled": true
  },
  {
    "name": "web_dev_mysql_1",
    "listen": "[::]:13306",
    "upstream": "database.domain:3306",
    "enabled": true
  }
]

Use ports outside the ephemeral port range to avoid random port conflicts. It's 32,768 to 61,000 on Linux by default, see /proc/sys/net/ipv4/ip_local_port_range.

3. Using Toxiproxy

To use Toxiproxy, you now need to configure your application to connect through Toxiproxy. Continuing with our example from step two, we can configure our Redis client to connect through Toxiproxy:

# old straight to redis
redis = Redis.new(port: 6380)

# new through toxiproxy
redis = Redis.new(port: 22220)

Now you can tamper with it through the Toxiproxy API. In Ruby:

redis = Redis.new(port: 22220)

Toxiproxy[:shopify_test_redis_master].downstream(:latency, latency: 1000).apply do
  redis.get("test") # will take 1s
end

Or via the CLI:

toxiproxy-cli toxic add -t latency -a latency=1000 shopify_test_redis_master

Please consult your respective client library on usage.

4. Logging

There are the following log levels: panic, fatal, error, warn or warning, info, debug and trace. The level could be updated via environment variable LOG_LEVEL.

Toxics

Toxics manipulate the pipe between the client and upstream. They can be added and removed from proxies using the HTTP api. Each toxic has its own parameters to change how it affects the proxy links.

For documentation on implementing custom toxics, see CREATING_TOXICS.md

latency

Add a delay to all data going through the proxy. The delay is equal to latency +/- jitter.

Attributes:

• latency: time in milliseconds
• jitter: time in milliseconds

down

Bringing a service down is not technically a toxic in the implementation of Toxiproxy. This is done by POSTing to /proxies/{proxy} and setting the enabled field to false.

bandwidth

Limit a connection to a maximum number of kilobytes per second.

Attributes:

• rate: rate in KB/s

slow_close

Delay the TCP socket from closing until delay has elapsed.

Attributes:

• delay: time in milliseconds

timeout

Stops all data from getting through, and closes the connection after timeout. If timeout is 0, the connection won't close, and data will be dropped until the toxic is removed.

Attributes:

• timeout: time in milliseconds

reset_peer

Simulate TCP RESET (Connection reset by peer) on the connections by closing the stub Input immediately or after a timeout.

Attributes:

• timeout: time in milliseconds

slicer

Slices TCP data up into small bits, optionally adding a delay between each sliced "packet".

Attributes:

• average_size: size in bytes of an average packet
• size_variation: variation in bytes of an average packet (should be smaller than average_size)
• delay: time in microseconds to delay each packet by

limit_data

Closes connection when transmitted data exceeded limit.

• bytes: number of bytes it should transmit before connection is closed

HTTP API

All communication with the Toxiproxy daemon from the client happens through the HTTP interface, which is described here.

Toxiproxy listens for HTTP on port 8474.

Proxy fields:

• name: proxy name (string)
• listen: listen address (string)
• upstream: proxy upstream address (string)
• enabled: true/false (default