- We deployed tarballs to production machines which unpacked to a single directory that included a virtualenv that had both all our code and all the modules we relied on, and anything else that the code needed to function that wasn't installed in a very basic RHEL install.
Ah, we're doing tarballs too but only for our code. We're having pip munge the global package list at the beginning of every deployment (somewhat dicey but with requirements files its easy to rollback package upgrades/downgrades) which does mean that packages can change underneath a running Python process :O
- We used the --relocatable option in virtualenv to remove all references to absolute paths, which meant we could copy the virtualenv around to various directories and machines and still have it work.
Hmmm this could work, I was under the impression --relocatable wasn't fully tested but if its works for you, we'll definitely take a look at it :)
- We had a series of makefiles that would make/update a virtualenv, and which worked on both mac and linux. We would use this both in development and when deploying. For several packages, we had to hand tune this to work on both mac and linux, but for most things, it Just Worked.
Yeah I took at look at virtualenvwrapper to handle the multi-environment thing but that was primarily geared for multiple apps. Probably got me more confused than necessary. I'll take a look at plain old virtualenv wioth scripts.
- When we deployed to production, we would unpack the tarball to a directory whose name included a version number for the push. We then had a symlink that pointed at the currently running version. This meant all we had to do to rollback a push was flip the symlink to the previous deployment directory, and restart. This rollback included any modules that changed (since they were in the virtualenv). I haven't seen any other way to reliably do this.
We do the exact same thing, minus the modules. We do have an issue with packages changing underneath versions but if we don't bounce the servers they should have the "old" modules already imported. We should fix this though :)
The one thing you mention that we didn't have to deal with was mixed 32/64-bit environments. One nasty solution is to have two build machines, one 32-bit and one 64-bit, but there's probably a better way...
> Not sure if pip lets you run configuration scripts during various stages of install and un-install?
As far as I can tell, you can run config scripts during installation. A good example of this would be Cython. An even crazier example of this would be uwsgi. As for uninstall I'm not sure. A lot of this has more to do with what setuptools/distribute can do not necessarily pip. Pip just makes it easy to enumerate/install/uninstall with the aid of PyPi, setuptools, distribute.
> Does pip let you depend on C libraries and other system features?
Pip isn't smart enough to track down C libraries. This is the part that kind of sucks but I don't know how pip would even do this. Python is cross-platform by nature. Being able to hook into what Windows DLLs, RPMs, debian packages you have to see what C dependencies you've satisfied seems like an ambitious endeavor. Its already hard enough to get a SINGLE package management system working well on its own :) Usually if I know I find myself missing a C library, I read the python package's installation notes, do apt-get or whatever to get all those dependencies I need, then run "pip install" I've had to do this for MySQL-python, pycrypto, and matplotlib thus far.
> How does pip handle obsoletes and transitive dependencies?
By obsolete you mean you need a newer version or do you mean you don't need that package at all anymore? As for transitive, do you mean like a chain of dependencies? I haven't run into any issues just yet... I think pip just goes out and installs everything for you. This primarily depends on how well people implement their setup.py's though.
You can explicitly specify which version of a package you want to install. For example, if you wanted to install an older version of Tornado,
pip install tornado==1.1
OR if you know you ONLY want tornado 2.0
pip install tornado==2.0
From my experience, pip has been able to fetch PYTHON dependencies if the author of the package wrote their setup.py correctly. I agree that things could be better with regards to C dependencies (MySQL-Python requiring libmysql5dev being particularly annoying) but this is hard to do as every environment has their own way of naming dependent libs.
Hi, I'm the author of the article. We've definitely looked at virtualenv but for right now we're just developing a single app. Thus far, we've been able to get away with munging the global package list but this could change in the near future. I tried playing around with virtualenv earlier this year but I couldn't figure out how to push directories OR make virtualenvs reliably relocatable. The main problems for us were/are:
1) We develop on macs
2) Our deploy environments are a mix of 32-bit/64-bit machines running Ubnutu
3) It wasn't clear if each deployment required its own virtualenv to start from scratch OR if we should reuse a virtualenv (which seemed to defeat the whole point of using virtualenv)
As for obsolete, you'll just have to manually uninstall the ones that were deprecated and install the new package.