Add functionality to copy revision on activation.

[arenoir]

This pr adds a config option copyToKey. When defined the activate function copies the value of the specified version to the copyToKey in redis. This makes it possible to serve the index page from nginx.

// deploy.js (sync)
module.exports = function(environment){
  var ENV = {
  };

  if (environment === 'production') {
    Env.redis = {
      copyToKey: 'my-app:active-version'
    }
  };
  return ENV;
};

Here is the corresponding nginx config.

#this sets a variable $app_version from a url parameter version or defaults to 'current-copy'
map $arg_version $app_version {
    default "active-version";
    ~^\w+ $arg_version;
}
upstream redisbackend{
    server 127.0.0.1:6379;
}
server {
    location / {
        set $redis_key my-app:$app_version;
        redis_pass redisbackend;
        default_type text/html;
    }
}

[ghedamat]

@arenoir thanks for this! It's an interesting use!

one thought,
maybe we should put your sample config in the README as well so folks can have an idea on the use case for this, not sure if in the config option section or in a separate section..

I also wonder if this could be done entirely in nginx (more curiosity than anything) but as @lukemelia pointed out out-of-band this is pretty good for simple use cases.

[arenoir]

@ghedamat, I will add the use case to the README. The NGINX redis module is very limited. I don't think it is possible to do this all in NGINX because multiple lookups are not possible.

I am also going to add the keyPrefix to the copyToKey. Perhaps copyToKey should be named copyToSuffix?

[lukemelia]

How about activeContentSuffix?

[arenoir]

@lukemelia activeContentSuffix sounds good to me.

Should I add a boolean that explicitly enables this feature or is the presence of activeContentSuffix enough?

[arenoir]

I changed the the key to activeContentSuffix updated the README and added a copyOnActivate config boolean.

The more I think about it the more I feel copyOnActivate should be default behavior. I mean whats the cost of one redis entry?

[lukemelia]

@arenoir I don't think we need an extra boolean flag. I think we can base it on the presence of activeContentSuffix. I am amenable to giving this a default value. Not sure what... maybe "active-content"? WDYT @achambers

Also need to consider how/whether this works with people using redis plugin without revision-data plugin.

[ghedamat]

@arenoir @lukemelia I'm ok with a default as well, and +1 for killing the boolean flag

You probably considered this already but, If I read the current version of the implementation correctly, if copyOnActivate is set we won't do the other part of the "normal" activation process, as mentioned above, I think we should do both or only the "normal" one.

[ghedamat]

@arenoir @lukemelia ping?

[arenoir]

@ghedamat, I removed the copyOnActivate boolean and rebased with master. So if activeContentSuffix is present it copies the content and also copies the active version key to the activationSuffix.

[ghedamat]

@arenoir sorry, could you do another rebase and then we take it for the final review/merge?

[arenoir]

@ghedamat, okay np I rebased with master... take a look.

[lukemelia]

Nice work @arenoir. Thanks!