為什么 open-uri 有時候是stringio 有時候返回 tmpfile?
我用ruby openuri 慢.
1.網絡io文件大小未定,作為類庫的設計者.
小文件太多,不好.IO性能差.
單個文件太大,如果都用memorybuffer,內存占用會非常的大.
設計者考慮2邊的靈活性.
2.我實際使用為什么會慢.因為網絡慢,丟包厲害.調整這個參數確實沒什么用.
在irb中調用
require 'open-uri'
zipfile = open("https://www.baidu.com/img/bdlogo.png")
require 'open-uri'
# Don't allow downloaded files to be created as StringIO. Force a tempfile to be created.
OpenURI::Buffer.send :remove_const, 'StringMax' if OpenURI::Buffer.const_defined?('StringMax')
OpenURI::Buffer.const_set 'StringMax', 2000000
irb(main):010:0> zipfile = open("https://www.baidu.com/img/bdlogo.png")
=> #<Tempfile:/var/folders/ss/kfvmx1195cj_zz3zb3tg0ch00000gn/T/open-uri20150617-13110-yt0suh>
修改配置后測試
require 'open-uri'
# Don't allow downloaded files to be created as StringIO. Force a tempfile to be created.
OpenURI::Buffer.send :remove_const, 'StringMax' if OpenURI::Buffer.const_defined?('StringMax')
OpenURI::Buffer.const_set 'StringMax', 0
irb(main):004:0> zipfile = open("https://www.baidu.com/img/bdlogo.png")
=> #<StringIO:0x007fe2f9008b68 @base_uri=#<URI::HTTPS https://www.baidu.com/img/
參考:
http://stackoverflow.com/questions/10496874/why-does-openuri-treat-files-under-10kb-in-size-as-stringio
When one does network programming, you allocate a buffer of a reasonably large size and send and read units of data which will fit in the buffer. However, when dealing with files (or sometimes things called BLOBs) you cannot assume that the data will fit into your buffer. So, you need special handling for these large streams of data.
(Sometimes the units of data which fit into the buffer are called packets. However, packets are really a layer 4 thing, like frames are at layer 2. Since this is happening a layer 7, they might better be called messages.)
For replies larger than 10K, the open-uri library is setting up the extra overhead to write to a stream objects. When under the StringMax size, it just includes the string in the message, since it knows it can fit in the buffer.