这个bash脚本有什么问题（供Foreman使用）

Question

I need an additional process to be run in development called Proxylocal (this allows external web services to hit http endpoints on my local machine).

In order to do this reliably though I would like to add the process into my Procfile. Since the process should not be run in production I am using this technique to do the switching.

My Procfile looks like this:

web: bundle exec unicorn -p $PORT -c ./config/unicorn.rb
redis: redis-server
worker: bundle exec sidekiq
proxylocal: bin/proxylocal

and bin/proxylocal looks like this:

#!/bin/bash
if [ "$RACK_ENV" == "development" ] 
  then
    proxylocal 5000 --host mypersonalmachine
fi

(I've never done any bash scripting so have no idea whether this is the correct syntax - I just copied it).

However each time I run foreman start it immediately exits with only the following error:

10:57:25 proxylocal.1 | started with pid 14935
10:57:25 proxylocal.1 | exited with code 0
10:57:25 system       | sending SIGTERM to all processes

Update1

If I remove the if statement and change bin/proxylocal to simply:

proxylocal 5000 --host mypersonalmachine

Then that does work successfully. Why then does the if statement make everything baulk?

Update 2

The following code does work as long as $RACK_ENV is equal to "development". I had to remove the double quotes around $RACK_ENV and to change the == to a single = .

if [  $RACK_ENV = "development" ]; then
    proxylocal 5000 --host brojure
fi

However... it only works as long as $RACK_ENV does equate to 'development'. When it doesn't it chokes.

Is it because Procfile needs a process ID?

A friend suggested that the issue may be that the Procfile is expecting a process ID to be returned from the script. So in the instance when we're not on development it's got nothing to process.

Is there a way in which I could spin up a zero-overhead process just to be able to return an ID. It's ugly but probably not too costly...

Answer 1

The problem is that when RACK_ENV is not "development" there is no process run so Foreman assumes that the script has crashed once it exits.

The right thing to do here is to create a "web" wrapper script that runs the proxy in development. Something like this:

#!/usr/bin/env bash

cleanup() {
  kill $proxy_pid
}

if [ "$RACK_ENV" == "development" ]; then
  proxylocal 5000 --host $PROXY_HOST &
  proxy_pid=$(cat thepidfile)
  trap cleanup EXIT
fi

bundle exec unicorn -p $PORT -c ./config/unicorn.rb

Answer 2

Please note that the answer from David Dollar should be the correct one as he wrote Foreman. However I still had problems getting it to work and so (for better or worse) this was what did eventually work for me:

# Procfile:

web: bundle exec unicorn -p $PORT -c ./config/unicorn.rb
redis: redis-server
worker: bundle exec sidekiq
proxylocal: bin/proxylocal_local

# bin/proxylocal_local

#!/usr/bin/env bash

if [ $RACK_ENV = "development" ]; then
  proxylocal 5000 --host $PROXYLOCAL_HOST 
else
  cat
fi

# .env

PROXYLOCAL_HOST=hostname_you_want_to_use

Also note that you'll need to chmod the proxylocal_local file so that it is executable.