Ruby 基于 RabbitMQ 场景的应用

stanwang — Sat, 01 Oct 2016 19:26:31 +0800

RabbitMQ 是基于 AMQP 的一种开源实现，使用 Erlang 语言开发，是一种重量级的消息中间件。特别适用于 SOA 场景下的消息异步处理，通过订阅者和发布者模式解耦各个模块的强依赖关系，一定程度上缓解分布式事务处理的复杂场景，通过 Ack 和 Nack 机制保证消息的相对必达性。

RabbitMQ 基础概念

概念	解释
Conection	对应一个 TCP 连接
Channel	相对 Conection 更高层次的连接抽象，约等于进程和线程的关系，建立和关闭的代价小于 Connection
Exchange	消息中转节点，一般会在这里设置各种路由规则
Queue	消息队列通道
Key	即 routing_key，消息路由依据，Queue 没有 bind routing_key 时默认路由 Queue 的 name

路由规则

Direct Exchange

直接路由即根据绑定的 routing_key 完全匹配时才将消息路由到指定的 Queue

Fanout Exchange

广播即路由消息至所有绑定到当前 Exchange 的所有队列

Topic Exchange

主题订阅，通过特定的匹配规则模糊路由消息，# 匹配 0 个或更多关键字，* 匹配一个关键字

场景策略

RabbitMQ 支持分布式消息负载路由，同级 N 个 Server 消费同一个 Queue，消息会根据策略（Round Robin）自动路由至一个消费者，如果期望多个消费者同时收取同一条消息，请每个消费者创建各自 Queue，并绑定至指定的 routing_key.

Ruby 使用 RabbitMQ

Ruby 中可以通过Bunny访问 RabbitMQ，这个 Gem 包提供了 RabbitMQ 的一些基础访问方法和很好的异常处理机制。

消息发送代码：

require "bunny"

conn = Bunny.new
conn.start

#创建连接通道
ch   = conn.create_channel

q    = ch.queue("hello")

#向指定Topic发送消息
ch.default_exchange.publish("Hello World!", :routing_key => q.name)

puts " [x] Sent 'Hello World!'"

conn.close

消息接收代码：

require "bunny"

conn = Bunny.new
conn.start

ch = conn.create_channel

#声明消费主题为hello
q = ch.queue("hello")

puts " [*] Waiting for messages in #{q.name}. To exit press CTRL+C"

#启用block避免手动loop
q.subscribe(:block => true) do |delivery_info, properties, body|
    puts "[x] Received #{body}"

    # 此处代码在接收到消息时将退出，注释掉可以一直消费直到中断
    # delivery_info.consumer.cancel
end

Bunny 支持各种容错性恢复，包括网络异常，如果因为特别场景需要关闭连接异常自动重连，可以在Bunny.new中

:automatic_recovery => false

参考地址

Windows 下面 Ruby 错误 Could not load 'active_record/connection_adapters/sqlite3_adapter'.

stanwang — Tue, 23 Sep 2014 14:09:24 +0800

Ruby 环境：ruby 2.1.3p242 (2014-09-19 revision 47630) [x64-mingw32]
Rails 环境：Rails 4.1.6
Widows 环境：win7 64bit

sqlite3-1.3.9-x64-mingw32.gemspec 文件中已修改为 s.require_paths= ["lib/sqlite3_native"]

相关的 dll 文件也放入 Ruby 的 Bin 文件之中，而且 Gemfile 文件中的 sqlite3 和 Gemfile.lock 中的版本一致，但是访问网页会抛出错误如下：

Could not load 'active_record/connection_adapters/sqlite3_adapter'. Make sure that the adapter in config/database.yml is valid. If you use an adapter other than 'mysql', 'mysql2', 'postgresql' or 'sqlite3' add the necessary adapter gem to the Gemfile.

异常链如下：

activesupport (4.1.6) lib/active_support/dependencies.rb:247:in `require'
activesupport (4.1.6) lib/active_support/dependencies.rb:247:in `block in require'
activesupport (4.1.6) lib/active_support/dependencies.rb:232:in `load_dependency'
activesupport (4.1.6) lib/active_support/dependencies.rb:247:in `require'
activerecord (4.1.6) lib/active_record/connection_adapters/sqlite3_adapter.rb:6:in `<top (required)>'
activesupport (4.1.6) lib/active_support/dependencies.rb:247:in `require'
activesupport (4.1.6) lib/active_support/dependencies.rb:247:in `block in require'
activesupport (4.1.6) lib/active_support/dependencies.rb:232:in `load_dependency'
activesupport (4.1.6) lib/active_support/dependencies.rb:247:in `require'
activerecord (4.1.6) lib/active_record/connection_adapters/connection_specification.rb:188:in `spec'
activerecord (4.1.6) lib/active_record/connection_handling.rb:50:in `establish_connection'
activerecord (4.1.6) lib/active_record/railtie.rb:129:in `block (2 levels) in <class:Railtie>'
activesupport (4.1.6) lib/active_support/lazy_load_hooks.rb:38:in `instance_eval'
activesupport (4.1.6) lib/active_support/lazy_load_hooks.rb:38:in `execute_hook'
activesupport (4.1.6) lib/active_support/lazy_load_hooks.rb:45:in `block in run_load_hooks'
activesupport (4.1.6) lib/active_support/lazy_load_hooks.rb:44:in `each'
activesupport (4.1.6) lib/active_support/lazy_load_hooks.rb:44:in `run_load_hooks'
activerecord (4.1.6) lib/active_record/base.rb:326:in `<module:ActiveRecord>'
activerecord (4.1.6) lib/active_record/base.rb:23:in `<top (required)>'
activerecord (4.1.6) lib/active_record/connection_adapters/abstract/connection_pool.rb:628:in `rescue in call'
activerecord (4.1.6) lib/active_record/connection_adapters/abstract/connection_pool.rb:619:in `call'
activerecord (4.1.6) lib/active_record/migration.rb:380:in `call'
actionpack (4.1.6) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
activesupport (4.1.6) lib/active_support/callbacks.rb:82:in `run_callbacks'
actionpack (4.1.6) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
actionpack (4.1.6) lib/action_dispatch/middleware/reloader.rb:73:in `call'
actionpack (4.1.6) lib/action_dispatch/middleware/remote_ip.rb:76:in `call'
actionpack (4.1.6) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
actionpack (4.1.6) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
railties (4.1.6) lib/rails/rack/logger.rb:38:in `call_app'
railties (4.1.6) lib/rails/rack/logger.rb:20:in `block in call'
activesupport (4.1.6) lib/active_support/tagged_logging.rb:68:in `block in tagged'
activesupport (4.1.6) lib/active_support/tagged_logging.rb:26:in `tagged'
activesupport (4.1.6) lib/active_support/tagged_logging.rb:68:in `tagged'
railties (4.1.6) lib/rails/rack/logger.rb:20:in `call'
actionpack (4.1.6) lib/action_dispatch/middleware/request_id.rb:21:in `call'
rack (1.5.2) lib/rack/methodoverride.rb:21:in `call'
rack (1.5.2) lib/rack/runtime.rb:17:in `call'
activesupport (4.1.6) lib/active_support/cache/strategy/local_cache_middleware.rb:26:in `call'
rack (1.5.2) lib/rack/lock.rb:17:in `call'
actionpack (4.1.6) lib/action_dispatch/middleware/static.rb:64:in `call'
rack (1.5.2) lib/rack/sendfile.rb:112:in `call'
railties (4.1.6) lib/rails/engine.rb:514:in `call'
railties (4.1.6) lib/rails/application.rb:144:in `call'
rack (1.5.2) lib/rack/lock.rb:17:in `call'
rack (1.5.2) lib/rack/content_length.rb:14:in `call'
rack (1.5.2) lib/rack/handler/webrick.rb:60:in `service'
E:/Tool/Ruby21-x64/lib/ruby/2.1.0/webrick/httpserver.rb:138:in `service'
E:/Tool/Ruby21-x64/lib/ruby/2.1.0/webrick/httpserver.rb:94:in `run'
E:/Tool/Ruby21-x64/lib/ruby/2.1.0/webrick/server.rb:295:in `block in start_thread'