Origin

Hynek Schlawack wrote an article about python application deployment using native linux packages. This project is an attempt to formalise some of those ideas into a more generic installation framework that follows those guidelines.

Build Host

Parcel uses the concept of a build host (or hosts) to simplify build procedures. The premise is thus: for each platform you want to target for deployment, you have a build host of the same architecture with the same software on it. Fabric connects to these machines and issues the build commands. This way the binary package created will be tailored to the final hardware.

These build hosts can be real machines, virtual machines, or cloud instances. It is important that the build hosts mirror your live deployment environment.

So for example, if your live servers were a mixture of Redhat on 64bit Intel architecture, and Debian on 32bit hardware, then you would have two build hosts, one Redhat 64bit and one Debian 32bit. You would then build rpms and debs of your project on those respective boxes.

The build hosts are specified to Fabric via the -H hosts command. For example the following will build two deb packages for the project for two different platforms:

$ fab -H debian32.localdomain,debian64.localdomain deb

Localhost as Hub

Parcel conforms to the idea of being the hub in all connections. Where everything is being pushed to and pulled from the local machine from which you issue your fab commands. So for instance, after a .deb is built, it is pulled back to the localhost. When the build host needs a new version of code, the code is copied across to the build machine. It is not checked out on the build machine. When completed packages are pushed into repositories, it is done from the local machine, not from the build host.

This has the advantages of keeping all connection authentication local to the developers machine. No private credentials need to be moved onto a build host to enable it to connect further. Once you have an ssh agent with your keys installed everything runs seamlessly.

It also helps keep the software that needs to be installed on the build host to a minimum. For example, mercurial or git does not need to be installed on the build host.

Build From Source, Deploy As Binary

Parcel performs builds on the build host from source rather than binaries. Then that source is honed down into a package that is distributed as a binary. Rather than builds being performed using eggs, or packages, all the source is checked out and a full source build is done. This ensures complete compatability with the deployment architecture and system arangement. Once this full source build is done, the resultant compiled files are packaged.

Parcel License

Copyright (c) 2012 Crispin Wellington.

Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED “AS IS” AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.