ruby - mongo db中的可尾游标超时

Question

我正在尝试在 ruby​​ 中创建一个 oplog 观察程序。到目前为止，我在下面想出了一个小脚本。

require 'rubygems'
require 'mongo'
db = Mongo::Connection.new("localhost", 5151).db("local")
coll = db.collection('oplog.$main')

loop do
cursor = Mongo::Cursor.new(coll, :tailable => true)
    while not cursor.closed?
        if doc = cursor.next_document
            puts doc
        else
            sleep 1
        end
    end
end

这个问题是，在 5 或 6 秒后，当它吐出大量数据时，它会超时并且我得到一个错误

C:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/gems/mongo-1.4.0/lib/../lib/mongo/connection.rb
:807:in `check_response_flags': Query response returned CURSOR_NOT_FOUND. Either an invalid c
ursor was specified, or the cursor may have timed out on the server. (Mongo::OperationFailure
)
        from C:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/gems/mongo-1.4.0/lib/../lib/mongo/
connection.rb:800:in `receive_response_header'
        from C:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/gems/mongo-1.4.0/lib/../lib/mongo/
connection.rb:768:in `receive'
        from C:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/gems/mongo-1.4.0/lib/../lib/mongo/
connection.rb:493:in `receive_message'
        from C:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/gems/mongo-1.4.0/lib/../lib/mongo/
connection.rb:491:in `synchronize'
        from C:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/gems/mongo-1.4.0/lib/../lib/mongo/
connection.rb:491:in `receive_message'
        from C:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/gems/mongo-1.4.0/lib/../lib/mongo/
cursor.rb:494:in `send_get_more'
        from C:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/gems/mongo-1.4.0/lib/../lib/mongo/
cursor.rb:456:in `refresh'
        from C:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/gems/mongo-1.4.0/lib/../lib/mongo/
cursor.rb:124:in `next_document'
        from n.rb:7
        from n.rb:6:in `loop'
        from n.rb:6

我不明白的是，当我能够看到实际数据时，它怎么会突然说找不到光标。我对 ruby​​ 很陌生，任何关于我必须采取的方向的想法都会对我有用。

Answer 1

解决方案是我需要有一个异常处理机制来捕获当光标读取相对较小的 oplog 中的最后一个文档时抛出的异常，每秒写入次数较多。由于游标到达 oplog 的末尾，它会抛出没有更多记录的异常。

require 'rubygems'
require 'mongo'
db = Mongo::Connection.new("localhost",5151).db("local")
coll = db.collection('oplog.$main')
loop do
cursor = Mongo::Cursor.new(coll, :timeout => false, :tailable => true)
    while not cursor.closed?
    begin
      if doc = cursor.next_document   
          puts "Timestamp"
          puts  doc["ts"]
          puts "Record"
          puts  doc["o"]
          puts "Affected Collection"
          puts doc["ns"]
      end
    rescue
        puts ""
        break
    end
  end
end

现在可以处理异常了。感谢 mongodb-user google 组向我指出这一点。