Question: Following is link to my init script for unicorn.
<https://gist.github.com/1466775>

Restart command has never worked for me. I am using upgrade to restart unicorn after each deploy. But whenever there is major changes like new gems being added, upgrade won't work. Recently, i replaced hoptoad gem with airbrake and it errors out saying 'uninitialized constant Airbrake (NameError)'. But when i stopped and started unicorn again, it worked fine. Does the problem lies in init script or its different problem?

Thanks.

Answer: 
According to your init script, "/bin/init.d/unicorn restart" sends HUP signal to unicorn master process

------cropped

```
restart|reload)
    sig HUP && echo reloaded OK && exit 0
    echo >&2 "Couldn't reload, starting '$CMD' instead"
    su - $USER -c "$CMD"

```

-----cropped

This is what HUP does to unicorn process :

reloads config file and gracefully restart all workers. If the “preload\_app” directive is false (the default), then workers will also pick up any application code changes when restarted. If “preload\_app” is true, then application code changes will have no effect.

What you are looking for is USR2 signal which your upgrade parameter to unicorn is already doing !

USR2 signal re-executes the running binary. A separate QUIT should be sent to the original process once the child is verified to be up and running.
I fixed this issue by changing my unicorn init.d script from

```
CMD="cd $APP_ROOT; bundle exec unicorn -D -c $APP_ROOT/config/unicorn.rb -E staging"

```

to this:

```
CMD="cd $APP_ROOT; BUNDLE_GEMFILE=$APP_ROOT/Gemfile bundle exec unicorn -D -c $APP_ROOT/config/unicorn.rb -E staging"

```

Which seems to point to the new bundle gemfile on every new release.
Taking inspiration from [this merge request](https://github.com/sosedoff/capistrano-unicorn/commit/c1e7a3f2794dd070367d0808ad102a6d20d39cf2#diff-14f6e151876ce4733900b16e3c2e8ddb)