#Gemfile添加如下两个gem包
gem 'mongoid', '~> 5.1.0'

gem 'mongo', '~> 2.4’

@client = Mongo::Client.new([host1,host2],:database=>'database_name',:user=>"user_name",:password=>"password")
@db = @client[:database_name].database
@collection_names = @db.collection_names
@collection_names.each do |collection_name|
   i=0
   @db[collection_name.to_sym].find.each do |x|
   　　puts x
   　　i = i + 1
   　　break if i == 10
   end
end

$redis = Redis.new(:host => "host", :port => 6379, :db => 2, :password=>"password")
$redis.keys

gem 'elasticsearch'

gem 'elasticsearch-rails'

gem 'elasticsearch-model'

$elastic = Elasticsearch::Client.new hosts: [{ host: 'host1',port: '9200',user: 'elastic',password: 'password'},{host: 'host1',port: '9200',user: 'elastic',password: 'password'}], randomize_hosts: true, log: false,send_get_body_as: "post" 
Elasticsearch::Model.client = $elastic
$elastic.search index:"index_name"

gem 'ruby-kafka', '~> 0.5.0'

kafka = Kafka.new(seed_brokers:["host:9092"])

consumer = kafka.consumer(:group_id=>"100")

consumer.subscribe("topic_name")

i=0

consumer.each_message do |meg|

  puts i=i+1

  puts meg.value

  break if i==10

end