Create a CLI to run daemons

[turicas]

This issue is actually related to lots of tasks and has some dependencies:

• Create a way to pass configuration to Broker, Router and Pipeliner classes - more on Broker should not ask for configuration (to Router) #56, Easily-configurable Router #57 and Easily-configurable Pipeliner #58;
• Parse a ini-style configuration file to pass it to from_configuration - more on Create helper to read configuration file and returns a dict #59;
• Create a way to run Broker, Router and Pipeliner's start methods as a daemon - more on Run daemons as actually Unix daemons #60;
• Create a command that parses command-line arguments, reads a configuration file and then run or stop daemons (this issue).

A sample config file should be like:

[global]
working_directory = /home/my_project/
api = tcp://127.0.0.1:5550
broadcast = tcp://127.0.0.1:5551
uid = my_user # optional, only if needs setuid
gid = my_group # optional, only if needs setgid

[router]
name = My Router
log_path = /tmp/router.log
pid_file = /tmp/router.pid

[pipeliner]
name = My Pipeliner
log_path = /tmp/pipeliner.log
pid_file = /tmp/pipeliner.pid

[broker]
name = My Broker
log_path = /tmp/broker.log
pid_file = /tmp/broker.pid
worker_module = workers
store_class = mymodule.MyStoreClass
number_of_workers = 40
store_custom_config_1 = my-value
store_custom_config_2 = other-value

All store_* directives inside broker section should be passed to Broker and then to StoreClass.__init__, as Broker should not ask for configuration to Router (as described in #56).

And the main usage should be like:

pypelinin -f pypelinin.conf <start|stop|restart> <all|router|pipeliner|broker>

Some command-line arguments are worth implementing:

• -f <config-file>: specify a configuration file to be used. - means stdin. If not specified, try /etc/pypelinin.conf, $HOME/.pypelinin
• -c <config-file>: specify a configuration file to be checked. - means stdin
• -g <config-file>: specify a configuration file to be generated (as an example). - means stdin
• --version, -V (or maybe -v): prints pypelinin version (pypelinin.__version__) and exit
• -h, --help: show help information about command-line arguments and exit

A manual page for pypelinin command is also desired, but it's not really needed on the first implementation.

[israelst]

Good shot!

[turicas]

Would be nice if we are able to specify a cluster shared cryptography key (for authentication of the daemons) in this config file too (but #11 needs to be implemented before it).

[turicas]

Currently, the "daemons" are not real daemons since they do not detach from tty, neither create new process session id and other things daemons should do by definition (read more about UNIX daemons at Wikipedia).
We should use the library python-daemon (described in PEP-3143) to implement it (it's very easy to use).

[turicas]

Since there are lots of tasks involved in this, I've created other issues (as dependencies of this one) and updated its description with dependencies and describing some possible command-line options.

[israelst]

We could use something like number_of_workers_per_cpu instead of number_of_workers in order to have more flexibility