Toxiproxy – simulate network and system conditions for chaos testing


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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 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

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

To take down all Redis instances:

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

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

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.


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


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
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

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

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

  # Return the key in Redis for the set of tags for the post.
  def tag_key

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'

    name: "toxiproxy_test_redis_tags",
    listen: "",
    upstream: ""

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 = 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

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
rescue Redis::CannotConnectError

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


Configuring a project to use Toxiproxy consists of three steps:

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

1. Installing Toxiproxy


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


$ wget -O toxiproxy-2.1.4.deb
$ sudo dpkg -i toxiproxy-2.1.4.deb
$ sudo service toxiproxy start


With Homebrew:

$ brew tap shopify/shopify
$ brew install toxiproxy

Or with MacPorts:


Toxiproxy for Windows is available for download at


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

$ docker pull
$ docker run --rm -it

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

$ docker run --rm --entrypoint="/toxiproxy-cli" -it list


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

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
    name: "shopify_test_redis_master",
    listen: "",
    upstream: ""
    name: "shopify_test_mysql_master",
    listen: "",
    upstream: ""

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: ___.
This makes sure there are no clashes between applications using the same

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

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 = 6380)

# new through toxiproxy
redis = 22220)

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

redis = 22220)

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

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 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


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


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


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.


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


  • rate: rate in KB/s


Delay the TCP socket from closing until delay has elapsed.


  • delay: time in milliseconds


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 delayed until the
toxic is removed.


  • timeout: time in milliseconds


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


  • timeout: time in milliseconds


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


  • 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


Closes connection when transmitted data exceeded limit.

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


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 (defaults to true on creation)

To change a proxy’s name, it must be deleted and recreated.

Changing the listen or upstream fields will restart the proxy and drop any active connections.

If listen is specified with a port of 0, toxiproxy will pick an ephemeral port. The listen field
in the response will be updated with the actual port.

If you change enabled to false, it will take down the proxy. You can switch it
back to true to reenable it.

Toxic fields:

  • name: toxic name (string, defaults to _)
  • type: toxic type (string)
  • stream: link direction to affect (defaults to downstream)
  • toxicity: probability of the toxic being applied to a link (defaults to 1.0, 100%)
  • attributes: a map of toxic-specific attributes

See Toxics for toxic-specific attributes.

The stream direction must be either upstream or downstream. upstream applies
the toxic on the client -> server connection, while downstream applies the toxic
on the server -> client connection. This can be used to modify requests and responses


All endpoints are JSON.

  • GET /proxies – List existing proxies and their toxics
  • POST /proxies – Create a new proxy
  • POST /populate – Create or replace a list of proxies
  • GET /proxies/{proxy} – Show the proxy with all its active toxics
  • POST /proxies/{proxy} – Update a proxy’s fields
  • DELETE /proxies/{proxy} – Delete an existing proxy
  • GET /proxies/{proxy}/toxics – List active toxics
  • POST /proxies/{proxy}/toxics – Create a new toxic
  • GET /proxies/{proxy}/toxics/{toxic} – Get an active toxic’s fields
  • POST /proxies/{proxy}/toxics/{toxic} – Update an active toxic
  • DELETE /proxies/{proxy}/toxics/{toxic} – Remove an active toxic
  • POST /reset – Enable all proxies and remove all active toxics
  • GET /version – Returns the server version number
  • GET /metrics – Returns Prometheus-compatible metrics

Populating Proxies

Proxies can be added and configured in bulk using the /populate endpoint. This is done by
passing a json array of proxies to toxiproxy. If a proxy with the same name already exists,
it will be compared to the new proxy and replaced if the upstream and listen address don’t match.

A /populate call can be included for example at application start to ensure all required proxies
exist. It is safe to make this call several times, since proxies will be untouched as long as their
fields are consistent with the new data.

CLI Example

$ toxiproxy-cli create -l localhost:26379 -u localhost:6379 redis
Created new proxy redis
$ toxiproxy-cli list
Listen          Upstream        Name  Enabled Toxics
====================================================================== localhost:6379  redis true    None

Hint: inspect toxics with `toxiproxy-client inspect proxyName>`

$ redis-cli -p 26379> SET omg pandas
OK> GET omg

$ toxiproxy-cli toxic add -t latency -a latency=1000 redis
Added downstream latency toxic 'latency_downstream' on proxy 'redis'
DEL omg
(integer) 1

$ redis-cli -p 26379> GET omg
(1.00s)> DEL omg
(integer) 1

$ toxiproxy-cli toxic remove -n latency_downstream redis
Removed toxic 'latency_downstream' on proxy 'redis'

$ redis-cli -p 26379> GET omg

$ toxiproxy-cli delete redis
Deleted proxy redis

$ redis-cli -p 26379
Could not connect to Redis at Connection refused


Toxiproxy exposes Prometheus-compatible metrics via its HTTP API at /metrics.
See for full descriptions

Frequently Asked Questions

How fast is Toxiproxy? The speed of Toxiproxy depends largely on your hardware,
but you can expect a latency of when no toxics are enabled. When running
with GOMAXPROCS=4 on a Macbook Pro we achieved ~1000MB/s throughput, and as high
as 2400MB/s on a higher end desktop. Basically, you can expect Toxiproxy to move
data around at least as fast the app you’re testing.

Can Toxiproxy do randomized testing? Many of the available toxics can be configured
to have randomness, such as jitter in the latency toxic. There is also a
global toxicity parameter that specifies the percentage of connections a toxic
will affect. This is most useful for things like the timeout toxic, which would
allow X% of connections to timeout.

I am not seeing my Toxiproxy actions reflected for MySQL. MySQL will prefer
the local Unix domain socket for some clients, no matter which port you pass it
if the host is set to localhost. Configure your MySQL server to not create a
socket, and use as the host. Remember to remove the old socket
after you restart the server.

Toxiproxy causes intermittent connection failures. 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.

Should I run a Toxiproxy for each application? No, we recommend using the
same Toxiproxy for all applications. To distinguish between services we
recommend naming your proxies with the scheme: ___.
For example, shopify_test_redis_master or shopify_development_mysql_1.


  • make. Build a toxiproxy development binary for the current platform.
  • make all. Build Toxiproxy binaries and packages for all platforms. Requires
    to have Go compiled with cross compilation enabled on Linux and Darwin (amd64)
    as well as goreleaser in your $PATH to
    build binaries the Linux package.
  • make test. Run the Toxiproxy tests.



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