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CIEL is a distributed execution engine for task- and data-parallel computation. It masks the complexity of distributed programming by providing distributed storage, transparent inter-machine communciation and transparent fault tolerance.

A CIEL job comprises one or more "tasks", each of which is associated with an "executor". This package includes several generic executors for integrating with UNIX utilities or programs that implement the CIEL executor interface. In addition, the following executors can be downloaded and installed separately:

• Skywriting is a scripting language for use with CIEL. It provides a "distributed thread" abstraction that enables you to write simple scripts that spawn tasks using any executor, and use control-flow features such as loops and conditionals.

• Java support is provided by writing classes that implement a Task Java interface. There is also experimental support for using Scala to write distributed threads.

• OCaml support is provided by using delimited continuations to serialise OCaml into CIEL tasks.

Installing CIEL

Before installing CIEL, you will need to install all of its dependencies:

Before running CIEL, you may need to install various dependencies. We develop CIEL on Ubuntu 10.04 and Fedora, and use the following packages; however, these may vary based on the exact version of your operating system.

+------------------------------------------------------+---------------------+---------------------+

Packages	apt-get	yum install
Python 2.5+	python	python
httplib2	python-httplib2	python-httplib2
simplejson	python-simplejson	python-simplejson
CherryPY 3.1.2+	python-cherrypy3	python-cherrypy3
PycURL	python-pycurl	python-pycurl
cURL	curl	curl
lighttpd	lighttpd	lighttpd
flup	python-flup	python-flup
+------------------------------------------------------+---------------------+---------------------+

To install CIEL, use the setup.py script. For example, you may type the following commands in the current directory:

    $ python setup.py build
    $ sudo python setup.py install

Running CIEL

A CIEL cluster contains one "master" process and one or more "worker" processes.

To start a master, use the following command:

$ ciel master

To start a worker on the same machine, use the following command:

$ ciel worker

To start a worker on a different machine, use the following command:

$ ciel worker -m http://${MASTER_HOSTNAME}:8000/

To find out about more options when running a master and workers, use the following command:

$ ciel [master|worker] --help

Testing CIEL

To run a simple CIEL job, first create a file called test.pack with the following contents:

{"start":
    {"handler": "stdinout",
     "args":
        {"args": 
            {"command_line": ["echo", "Hello, world!"]}
        }
    },
 "result": [{"__decode_ref__": "noop"}]
}

This is a simple example of a "package file", which is used to specify a CIEL job. Package files are the most flexible way of specifying a CIEL job, but some executors (such as Skywriting) provide simpler ways to create simple jobs.

To execute the package file, first start a cluster, then type the following command:

$ ciel run test.pack