Reuse Redis connection in allow_domain method

[waynerobinson]

Sorry for a potentially dumb question, I've got no experience with Lua.

But is it possible to reuse the Redis connection within the allow_domain method for looking up permissable domains from a set stored there?

We've played with a couple of different options, but would really like to keep a whitelist of domains in a DB somewhere it refers to and since there's already Redis support baked in, we may as well use it.

[GUI]

Not a dumb question at all!

You could establish a new redis connection inside the allow_domain callback, but it doesn't look like we have a super-easy way to reuse the same Redis connection that the storage mechanism would already have instantiated. But I think that's a good idea, so we could certainly look at ways to better expose that part of the storage API to the allow_domain callback for a future release (or pull requests are always welcome).

In the meantime, here's a workaround that I think might work to allow you to leverage the same connection in both places:

local function get_redis_instance(redis_options)
  local instance = ngx.ctx.auto_ssl_redis_instance
  if instance then
    return instance
  end

  instance = redis:new()
  local ok, err

  if redis_options["socket"] then
    ok, err = instance:connect(redis_options["socket"])
  else
    ok, err = instance:connect(redis_options["host"], redis_options["port"])
  end
  if not ok then
    return false, err
  end

  if redis_options["auth"] then
    ok, err = instance:auth(redis_options["auth"])
    if not ok then
      return false, err
    end
  end

  ngx.ctx.auto_ssl_redis_instance = instance
  return instance
end

auto_ssl = (require "resty.auto-ssl").new()
local redis_options = {
  host = "10.10.10.1"
}
auto_ssl:set("redis", redis_options)
auto_ssl:set("allow_domain", function(domain)
  local redis_instance, instance_err = get_redis_instance(redis_options)
  if instance_err then
    return nil, instance_err
  end

  local res, err = redis_instance:get("WHATEVER...")
  -- Do whatever else you need with redis_instance.
end)
auto_ssl:init()

It's a bit ugly, but basically I'm just copying the private get_redis_instance method out of the Redis storage adapter: https://github.com/GUI/lua-resty-auto-ssl/blob/v0.10.3/lib/resty/auto-ssl/storage_adapters/redis.lua#L5-L32 Since both functions will cache the redis connection on the ngx.ctx.auto_ssl_redis_instance context variable, then which ever version of get_redis_instance gets called first should be the only one that actually establishes a connection.

But again, I think providing a cleaner way to get at this connection object directly from the storage API would be better long term.

[waynerobinson]

Thanks for this! I'll check it out.

[aviatrix]

Hey @GUI , has anything been done to enable this ?

[luto]

@aviatrix I don't know of any changes regarding this. Right now nobody knows what reusing that object would even look like, for a users point of view. Is there an interface idea you'd like to work out and propose? I'll be glad to give you some pointers on how to implement it.

[aviatrix]

@luto Right now i've settled for the get_redis_instance example given by @GUI in the comments above, however that is sub optimal in my opinion. On first thought maybe exposing the get_redis_instance as public static method should suffice so we can call that function inside the auto_ssl like this : auto_ssl:get_redis_instance(). I'm not familiar with Lua or how it works or if this is even possible.

[aviatrix]

One small caveat : if you don't put local redis = require "resty.redis" on the top of init_by_lua_block there is a chance it will blow up when trying to init redis :)

[GUI]

Well, better late than never, but this should finally be easier in the v0.12.0 release. You can now access the redis connection via auto_ssl.storage.adapter:get_connection(), and the auto_ssl instance is passed as the second argument to the allow_domain callback. Thanks for the idea!

[gohai]

@GUI Is it possible to get to ssl_options through the auto_ssl instance? Thanks!