Stack VS Queue Flexibility

[joshuasager]

Hey @mperham,

I am trying to leverage connection_pool in order to maintain a collection of open HTTPS connections.

The motivation for this is that I am trying to make repeated requests to an API server, however, re-negotiating SSL over the web on every request is quite slow.

Right now, I have the following implementation:
config/puma.rb

...

preload_app!

on_worker_boot do
  RequestPool.initialize_connections(thread_count)

  ActiveSupport.on_load(:active_record) do
    ActiveRecord::Base.establish_connection
  end
end

lib/request_pool.rb

require 'http'
require 'connection_pool'

# @note Each key maps to a single connection.
# @note To add a new URL to the connection pool, you must first add it to config/connections.yml
# @example Stores connections to multiple servers in a single hash.
#   RequestPool.new('https://www.google.ca').connection do |conn, ssl_context|
#       conn.get('/route', ssl_context: ssl_context)
#   end
class RequestPool
    @@conn = {}

    SSL_VERSION = :TLSv1_2
    SSL_CIPHERS = "ALL:!ADH:!EXPORT:!SSLv2:RC4+RSA:+HIGH:+MEDIUM:-LOW".freeze

    def self.initialize_connections(size)
        self.config.each do |url|
            @@conn[url] = ConnectionPool.new(size: size) { HTTP.persistent(url).timeout(:per_operation, connect: 10, read: 15) }
        end
    end

    def initialize(base_url)
        raise ArgumentError unless @@conn.has_key? base_url
        @base_url = base_url
    end

    # @note we call .to_s to ensure the respones gets flushed. 
    #   See https://github.com/httprb/http/wiki/Persistent-Connections-(keep-alive) for more details
    def connection
        @@conn[@base_url].with do |conn|
            response = yield conn, ssl_config
            response.to_s
            response
        end
    end

    private

    def self.config
        YAML.load_file("#{Rails.root}/config/connections.yml")[Rails.env]
            .values
    end

    def ssl_config
        OpenSSL::SSL::SSLContext.new.tap do |ctx|
            ctx.ssl_version = SSL_VERSION
            ctx.ciphers     = SSL_CIPHERS
        end
    end
end

If connection_pool were to have the option of using a Stack instead of a Queue, then, the HTTPS connections would be reused more frequently before going stale.

Would this be something that the gem would be willing to incorporate?

[mperham]

I believe @drbrain did some refactoring to make connection_pool better for pooling persistent http connections. I would search the issues/PRs for his input.

[drbrain]

net-http-persistent uses connection_pool to maintain persistent connections for HTTP requests including TLS requests. I think you're looking for TimedStackMulti in these files as ConnectionPool by default works with a homogenous connection pool while HTTP connections need a heterogenous connection pool.