Avoiding deployment gem-fail downtime while using Passenger, bundler & git-based deploys

I'm deploying a Rails 3 app on Passenger 3.0.7 using capistrano and git-based deployment, similar to GitHub's setup: https://github.com/blog/470-deployment-script-spring-cleaning -- this means the app operates entirely out of one directory, with no /releases/123456 and symlink switching.

If we've added any gems our app starts throwing 500 errors during deployment, during the "bundle:install" phase, but before deploy:restart. The code has been updated and it seems like passenger is already starting to use it, and required gems can't be found yet.

This is not caused by new workers being spun up, as I've tried setting the Passenger idle_time to 0 and max_instances and min_instances to the same value, so that workers are never spun down.

Running on Linux with ruby-ee 1.8.7-2011.03. Sample error from Passenger: https://gist.github.com/54794e85d2c799e4f697

I'开发者_如何学Gove also considered doing "two-directory" git-based deployment as a hack -- swapping in the new code once the bundle is complete. Ideas welcome.

Go with the two-directory deployment. Apart from avoiding the 500s during deployment, this will also act as a safety net if you need to rollback during/after deployment.