##Quick Install

Go to your existing application containing fig.yml config. And then:

$ pip install compose-monkey
$ docker-compose --monkey up

Note : -m / --monkey is the flag to activate ComposeMonkey and without that flag, docker-compose will run as usual.

If everything goes fine, a UI server gets started at the port 2020 (configurable) exposed on the host machine.

##What is Compose Monkey Compose Monkey is a resiliency testing tool for applications running through docker-compose. It is a fork of compose which adds an opt-in feature to test the scenarios where the downstream services become flaky/down/slow.

It also provides a UI port to control the behavior of all the downstream services in real time. On start, all the downstream services behave as normal i.e. the proxy exhibits dummy behvaior.

Compose Monkey :

• Smartly suggests port and TCP protocol for the destination link
• Option to skip proxy creation for any link
• UI controller to change the behvaior of the link in real time.

##How it works Internally, it uses a package Vaurien which provides TCP proxy and behavior simulation. For every link, ComposeMonkey injects a Vaurien container between the source and the destination service. To start a Vaurien container, it needs the TCP protocol and the port needed to talk to the destination. ComposeMonkey makes a best effort strategy to find those and shows them to the user as defaults.

Destination Port is found by searching for exposed port of the destination, if any. Protocol is suggested naively by checking the downstream service name. User has the option to provide port/protocol of their choice if not satisfied with the defaults.

      +------------+           +-------------+            
      |            |           |             |            
      |    WEB     +----------->    REDIS    |            
      |            |           |             |            
      +------------+           +-------------+            
                                                          
                     Without --monkey                     
                                                          
                                                           

|                                                               |
|---------------------------------------------------------------|
|                                                               |

                                                          
+------------+        +------------+        +------------+
|            |        |            |        |            |
|    WEB     +--------> COMPOSMNKY +-------->    REDIS   |
|            |        |            |        |            |
+------------+        +-----^------+        +------------+
                            |                             
                            |                             
                            |                             
                      +-----+------+                      
                      |            |                      
                      |     UI     |                      
                      |            |                      
                      +------------+                      
                                                          
                                                          
                       With --monkey                      

##Future Work

ComposeMonkey can also be built and packaged outside of docker-compose. This can be implemented by creating a temporary fig.yml from the original config yaml file which has a vaurien container entry for each downstream link and single UI container which links all the proxy containers. This work is still in development.