The Basics

  1. Application
  2. twistd
  3. tap2deb
  4. tap2rpm


Twisted programs usually work with twisted.application.service.Application. This class usually holds all persistent configuration of a running server -- ports to bind to, places where connections to must be kept or attempted, periodic actions to do and almost everything else. It is the root object in a tree of services implementing IService.

Other HOWTOs describe how to write custom code for Applications, but this one describes how to use already written code (which can be part of Twisted or from a third-party Twisted plugin developer). The Twisted distribution comes with an important tool to deal with Applications, twistd.

Applications are just Python objects, which can be created and manipulated in the same ways as any other object.


The Twisted Daemon is a program that knows how to run Applications. This program is twistd(1). Strictly speaking, twistd is not necessary -- fetching the application, getting the IService component, calling startService, scheduling stopService when the reactor shuts down, and then calling could be done manually. twistd(1), however, supplies many options which are highly useful for program set up.

twistd supports choosing a reactor (for more on reactors, see Choosing a Reactor), logging to a logfile, daemonizing and more. twistd supports all Applications mentioned above -- and an additional one. Sometimes it is convenient to write the code for building a class in straight Python. One big source of such Python files is the doc/examples directory. When a straight Python file which defines an Application object called application is used, use the -y option.

When twistd runs, it records its process id in a file (this can be configured via a command line switch). In order to shutdown the twistd process, kill that pid (usually you would do kill `cat`).

As always, the gory details are in the manual page.


For Twisted-based server application developers who want to deploy on Debian, Twisted supplies the tap2deb program. This program wraps a Twisted Application file (of any of the supported formats -- Python, source, xml or pickle) in a Debian package, including correct installation and removal scripts and init.d scripts. This frees the installer from manually stopping or starting the service, and will make sure it goes properly up on startup and down on shutdown and that it obeys the init levels.

For the more savvy Debian users, the tap2deb also generates the source package, allowing her to modify and polish things which automated software cannot detect (such as dependencies or relationships to virtual packages). In addition, the Twisted team itself intends to produce Debian packages for some common services, such as web servers and an inetd replacement. Those packages will enjoy the best of all worlds -- both the consistency which comes from being based on the tap2deb and the delicate manual tweaking of a Debian maintainer, insuring perfect integration with Debian.


tap2rpm is similar to tap2deb, except that it generates RPMs for Redhat and other related platforms.


Version: 10.0.0