Proxy for simulating real-world distributed system failures to improve resilience in your applications.
Introduction
Muxy is a proxy that mucks with your system and application context, operating at Layers 4, 5 and 7, allowing you to simulate common failure scenarios from the perspective of an application under test; such as an API or a web application.
If you are building a distributed system, Muxy can help you test your resilience and fault tolerance patterns.
Contents
- Introduction - Contents
- Features
- Installation - On Mac OSX using Homebrew - Using Go Get
- Using Muxy - 5-minute example - Muxy as part of a test suite - Notes
- Proxies and Middlewares - Proxies - HTTP Proxy - TCP Proxy - Middleware - Delay - HTTP Tamperer - Network Shaper - TCP Tamperer - Logger
- Configuration Reference
- Examples - Hystrix
- Usage with Docker
- Extending Muxy - Proxies - Middleware
- Contributing
Features
- Ability to tamper with network devices at the transport level (Layer 4)
- Ability to tamper with the TCP session layer (Layer 5)
- ...and HTTP requests/responses at the HTTP protocol level (Layer 7)
- Supports custom proxy routing (aka basic reverse proxy)
- Advanced matching rules allow you to target specific requests
- Introduce randomness into symptoms
- Simulate real-world network connectivity problems/partitions for mobile devices, distributed systems etc.
- Ideal for use in CI/Test Suites to test resilience across languages/technologies
- Simple native binary installation with no dependencies
- Extensible and modular architecture
- An official Docker container to simplify uses cases such as Docker Compose
Installation
Download a release for your platform and put it somewhere on the PATH.
On Mac OSX using Homebrew
If you are using Homebrew you can follow these steps to install Muxy:
brew install https://raw.githubusercontent.com/mefellows/muxy/master/scripts/muxy.rb
Using Go Get
go get github.com/mefellows/muxy
Using Muxy
Muxy is typically used in two ways:
- In local development to see how your application responds under certain conditions
- In test suites to automate resilience testing
5-minute example
-
Install Muxy
-
Create configuration file
config.yml:# Configures a proxy to forward/mess with your requests # to/from www.onegeek.com.au. This example adds a 5s delay # to the response. proxy: - name: http_proxy config: host: 0.0.0.0 port: 8181 proxy_host: www.onegeek.com.au proxy_port: 80 # Proxy plugins middleware: - name: http_tamperer config: request: host: "www.onegeek.com.au" # Message Delay request/response plugin - name: delay config: request_delay: 1000 response_delay: 500 # Log in/out messages - name: logger
-
Run Muxy with your config:
muxy proxy --config ./config.yml -
Make a request to www.onegeek.com via the proxy:
time curl -v -H"Host: www.onegeek.com.au" http://localhost:8181/. Compare that with a request direct to the website:time curl -v www.onegeek.com.au- it should be approximately 5s faster.
That's it - running Muxy is a matter of configuring one or more Proxies, with 1 or more Middleware components defined in a simple YAML file.
Muxy as part of a test suite
- Create an application
- Build in fault tolerence (e.g. using something like Hystrix)
- Create integration tests
- Run Muxy configuring a proxy such as HTTP, and one or more symptoms such as network latency, partition or HTTP error
- Point your app at Muxy
- Run tests and check if system behaved as expected
- Profit!
Notes
Muxy is a stateful system, and mucks with your low-level (system) networking interfaces and therefore cannot be run in parallel with other tests. It is also recommended to run within a container/virtual machine to avoid unintended consequences (like breaking Internet access from the host).
Proxies and Middlewares
Proxies
HTTP Proxy
Simple HTTP(s) Proxy that starts up on a local IP/Hostname and Port.
Example configuration snippet:
proxy:
- name: http_proxy
config:
## Proxy host details
host: 0.0.0.0
protocol: http
port: 8181
## Proxy target details
proxy_host: 0.0.0.0
proxy_port: 8282
proxy_protocol: https
## Certificate to present to Muxy clients (i.e. server certs)
proxy_ssl_key: proxy-server/test.key
proxy_ssl_cert: proxy-server/test.crt
## Certificate to present to Muxy proxy targets (i.e. client certs)
proxy_client_ssl_key: client-certs/cert-key.pem
proxy_client_ssl_cert: client-certs/cert.pem
proxy_client_ssl_ca: client-certs/ca.pem
## Enable this to proxy targets we don't trust
# insecure: true # allow insecure https
# Specify additional proxy rules. Default catch-all proxy still
# applies with lowest matching precedence.
# Request matchers are specified as valid regular expressions
# and must be properly YAML escaped.
# See https://github.com/mefellows/muxy/issues/11 for behaviour.
- request:
method: 'GET|DELETE'
path: '^\/foo'
host: '.*foo\.com'
pass:
path: '/bar'
scheme: 'http'
host: 'bar.com'
TCP Proxy
Simple TCP Proxy that starts up on a local IP/Hostname and Port, forwarding traffic to the specified proxy_host on proxy_port.
Example configuration snippet:
proxy:
- name: tcp_proxy
config:
host: 0.0.0.0 # Local ip/hostname to bind to and accept connections.
port: 8080 # Local port to bind to
proxy_host: 0.0.0.0
proxy_port: 2000
nagles_algorithm: true
packet_size: 64
Middleware
Middleware have the ability to intervene upon receiving a request (Pre-Dispatch) or before sending the response back to the client (Post-Dispatch). In some cases, such as the Network Shaper, the effect is applied before any request is made (e.g. if the local network device configuration is altered).
Delay
A basic middleware that simply adds a delay of delay milliseconds to the request or response.
Example configuration snippet:
middleware:
- name: delay
config:
request_delay: 1000 # Delay in ms to apply to request to target
response_delay: 500 # Delay in ms to apply to response from target
# Specify additional matching rules. Default is to apply delay to all
# requests on all http proxies.
# Request matchers are specified as valid regular expressions
# and must be properly YAML escaped.
# See https://github.com/mefellows/muxy/issues/11 for behaviour.
matching_rules:
- method: "GET|DELETE"
path: "^/boo"
host: 'foo\.com'
HTTP Tamperer
A Layer 7 tamperer, this plugin allows you to modify response headers, status code or the body itself.
Example configuration snippet:
middleware:
- name: http_tamperer
config:
request:
host: "somehost" # Override Host header that's sent to target
path: "/" # Override the request path
method: "GET" # Override request method
headers:
x_my_request: "foo" # Override request header
content_type: "application/x-www-form-urlencoded"
content_length: "5"
cookies: # Custom request cookies
- name: "fooreq"
value: "blahaoeuaoeu"
domain: "localhost"
path: "/foopath"
secure: true
rawexpires: "Sat, 12 Sep 2015 09:19:48 UTC"
maxage: 200
httponly: true
body: "wow, new body!" # Override request body
response:
status: 201 # Override HTTP Status code
headers: # Override response headers
content_length: "27"
x_foo_bar: "baz"
body: "my new body" # Override response body
cookies: # Custom response cookies
- name: "foo"
value: "blahaoeuaoeu"
domain: "localhost"
path: "/foopath"
secure: true
rawexpires: "Sat, 12 Sep 2015 09:19:48 UTC"
maxage: 200
httponly: true
# Specify additional matching rules. Default is to apply delay to all
# requests on all http proxies.
# Request matchers are specified as valid regular expressions
# and must be properly YAML escaped.
# See https://github.com/mefellows/muxy/issues/11 for behaviour.
matching_rules:
- method: "GET|DELETE"
path: "^/boo"
host: 'foo\.com'
Network Shaper
The network shaper plugin is a Layer 4 tamperer, and requires root access to work, as it needs to configure the local firewall and network devices. Using the excellent Comcast library, it can shape and interfere with network traffic, including bandwidth, latency, packet loss and jitter on specified ports, IPs and protocols.
NOTE: This component only works on MacOSX, FreeBSD, Linux and common *nix flavours.
Example configuration snippet:
middleware:
- name: network_shape
config:
latency: 250 # Latency to add in ms
target_bw: 750 # Bandwidth in kbits/s
packet_loss: 0.5 # Packet loss, as a %
target_ips: # Target ipv4 IP addresses
- 0.0.0.0
target_ips6: # Target ipv6 IP addresses
- "::1/128"
target_ports: # Target destination ports
- "80"
target_protos: # Target protocols
- "tcp"
- "udp"
- "icmp"
device: "lo" # defaults to eth0
TCP Tamperer
The TCP Tamperer is a Layer 5 tamperer, modifying the messages in and around TCP sessions. Crudely, you can set the body of inbound and outbound TCP packets, truncate the last character of messages or randomise the text over the wire.
- name: tcp_tamperer
config:
request:
body: "wow, new request!" # Override request body
randomize: true # Replaces input message with a random string
truncate: true # Removes last character from the request message
response:
body: "wow, new response!" # Override response body
randomize: true # Replaces response message with a random string
truncate: true # Removes last character from the response message
Logger
Log the in/out messages, optionally requesting the output to be hex encoded.
Example configuration snippet:
middleware:
- name: logger
config:
hex_output: false # Display output as Hex instead of a string
Configuration Reference
Refer to the example YAML file for a full reference.
Examples
Hystrix
Using the Hystrix Go library, we use Muxy to trigger a circuit breaker and return a canned response, ensuring we don't have downtime. View the example.
Usage with Docker
Download the Docker image by running:
docker pull mefellows/muxy
After creating a [config](#configuration-reference] file (let's assume it's at ./conf/config.yml), and assuming you are proxying something on port 80, you can now run the image locally:
docker run \
-d \
-p 80:80 \
-v "$PWD/conf":/opt/muxy/conf \
--privileged \
mefellows/muxy
You should now be able to hit this Docker container and simulate any failures as per usual. e.g. curl docker:80/some/endpoint.
The Hystrix example above has a detailed example on how to use Muxy with a more complicated system, using Docker Compose to orchestrate a number of containers.
Extending Muxy
Muxy is built as a series of configurable plugins (using Plugo) that must be specified in the configuration file to be activated. Start with a quick tour of Plugo before progressing.
Proxies
Proxies must implement the Proxy interface, and register themselves via PluginFactories.register to be available at runtime. Take a look at the HTTP Proxy for a good working example.
Middleware
Middlewares implement the Middleware interface and register themselves via PluginFactories.register to be available at runtime. Take a look at the HTTP Delay for a good working example.
Contributing
See CONTRIBUTING.
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