Test nginx config before deploying

[wosephjeber]

Is it possible to test the nginx config for errors with nginx -t before deploying? I've deployed a few bad builds of a proxy server (still in development, thankfully, so it didn't impact any production services) due to a bad config.

[beanieboi]

hey,

i really like that idea, would you be able to come up with a PR to implement the changes?

ben

[beanieboi]

i just had another look into this and i don't think it's possible. we need to evaluate the config.erb to get the value for the $PORT and probably other environment variables. this means we only have the full complete config during dyno boot up and not during the build phase. i'm not sure how we can evaluate a partial config.

[privettoli]

@beanieboi, maybe at least before deployment? I was trying to use gunzip (#26) and couldn't understand the reason for failing deployment.
@wosephjeber, do you think we could come up with the PR?

[jmorrell]

Could this test be done in the start-nginx script? https://github.com/heroku/heroku-buildpack-nginx/blob/master/bin/start-nginx

[hom3chuk]

I'm not 100% sure on Heroku's flow and that exiting during launch script will stop build from being rolled out. But if it is like that, this PR should do the job

[beanieboi]

It will not. During the build we only copy the needed files into your app (see https://github.com/heroku/heroku-buildpack-nginx/blob/master/bin/compile)

If we do this in the start-nginx script it will not prevent it from being released, your app will still crash during startup.

[jamemackson]

if there were a way to run this locally, that might allow us to catch config errors before it even hits heroku. is that at all a possibility?

[blgo]

if there were a way to run this locally, that might allow us to catch config errors before it even hits heroku. is that at all a possibility?

Customise the official nginx Docker image using your own Dockerfile with your own environment variables in it:

1. install Ruby to get "erb"
2. override the entry point, and add the command erb /etc/nginx/nginx.conf.erb > /etc/nginx/nginx.conf
3. Finally launch the original entrypoint sh ./docker-entrypoint.sh $*