From: Brian Candler <b.candler@...>
Date: 2008-12-24T18:47:49+09:00
Subject: Re: Net::HTTPResponse#read_body usable for timing?

Denis Haskin wrote:
> Does anyone know if read_body is synchronous wrt to the network reads?

The source will be installed somewhere like 
/usr/lib/ruby/1.8/net/http.rb - it's all in Ruby and fairly easy to 
understand. Look for read_body and read_body_0.

However, you can see it relies on some Ruby internals, such as 
Socket#read calling << on the dest buffer object; see ReadAdapter in 
net/protocol.rb (*)

Basically, you'll get a separate Socket#read call for each chunk if 
you're getting HTTP/1.1 chunked encoding for your result body, and a 
single Socket#read call for non-chunked with Content-Length. tcpdump 
should show what you're actually getting.

What I don't know is, if you do Socket#read(1_000_000, dest) is whether 
Ruby breaks the read up into smaller ones and calls << onto dest for 
each chunk, and if so, what buffer size it's using. That would involve 
looking at the C source code.

HTH,

Brian.

(*) In fact Net::HTTP violates Ruby's own documentation, which says 
explicitly that the result buffer may only be a String object.

---------------------------------------------------------------- IO#read
     ios.read([length [, buffer]])    => string, buffer, or nil
------------------------------------------------------------------------
     Reads at most _length_ bytes from the I/O stream, or to the end of
     file if _length_ is omitted or is +nil+. _length_ must be a
     non-negative integer or nil. If the optional _buffer_ argument is
     present, it must reference a String, which will receive the data.

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