Shapeshifter

Shapeshifter is a tool for interacting with remote servers. It consists of a controller script (ssc) and a set of modules which run on the servers with which we want to interact. There is a small set of core, bootstrap modules. All modules (including the bootstrap ones) can be uploaded and replaced at run time. Use cases include:

• automatic deployment of applications built in a continuous integration environment
• monitoring and management of processes running on servers via a web interface

Quick Demo

1. Make sure you have Python 2.7 installed
2. Clone git://github.com/mmakowski/shapeshifter.git
3. Copy the bootstrap directory to some temporary place on your computer and run webserver.py in there.
4. In the root of your clone run:
   • ssc.py localhost PUT /ssmodule/hello module=file:modules/hello.py
   • ssc.py localhost POST /hello/World

You can play around with modifying modules/hello.py and then running the two ssc command above to update and execute it.

How it Works

Let's see what happens in the demo above:

1. webserver.py starts a process which listens for HTTP connections on port 5457.
2. ssc.py sends a PUT request to the listening process with URI /ssmodule/hello and body of type multipart/form-data containing the contents of modules/hello.py file.
3. The listener receives the request; it takes the first part of the URI, ssmodule, loads a module with this name and calls a PUT() function (corresponding to the HTTP method used) in it, passing in the remainder of the URI ("hello") as an argument.
4. ssmodule.PUT() creates a file hello.py writing to it the content retrieved from the request body.
5. the second invocation of ssc sends a POST request with URI /hello/World.
6. The listener processes the requst by invoking hello.POST() function (defined in the module created in response to the previous request) and passing to it "World".
7. hello.POST() prints the greeting on the standard output.

Usage

ssc.py <targets> <method> <URI> [<data>]

• <targets>: a comma-separated list of machines to which requests are to be sent.
• <method>: HTTP method; currently supported methods are DELETE, GET, POST and PUT.
• <URI>: the URI to be requested. The first element of it (up to the first /) determines the module which will be invoked.
• <data>: a set of key-value pairs to be sent as form data in the format: <key_1>=<value_1>,...,<key_n>=<value_n>. If a value is of the format file:<path> then the contents of file denoted by <path> will be sent.