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Bug #16672

Updated by jmreid (Justin Reid) 9 months ago

When using net/http to make a request to a resource, the default request headers are the following (when you have ZLIB available): 
 `"accept-encoding"=>["gzip;q=1.0,deflate;q=0.6,identity;q=0.3"], "accept"=>["*/*"], "user-agent"=>["Ruby"]` 

 This means that a resource will return a gzipped response if it can provide it. Take this URL for example: 
 `https://storage.googleapis.com/justin-reid-test/test.js` 

 This is a JS file that has a `content-length` of `2733` when gzipped and `9995` when inflated: 

 ``` 
 curl --silent GET "https://storage.googleapis.com/justin-reid-test/test.js" -H "accept-encoding: gzip;q=1.0,deflate;q=0.6,identity;q=0.3" | wc -c 
 2733 

 curl --silent GET "https://storage.googleapis.com/justin-reid-test/test.js" | wc -c 
 9995 
 ``` 


 When making a simple request for this asset using net/http: 
 ``` 
 uri = URI('https://storage.googleapis.com/justin-reid-test/test.js') 
 res = Net::HTTP.get_response(uri) 
 ``` 

 Ruby will (https://github.com/ruby/ruby/blob/f08cd708b11dd5b293986b92bb5e227731665b36/lib/net/http/response.rb#L264-L278): 
 - Delete the `content-encoding` header 
 - inflate the body 
 - return the inflated body 

 The issue here is that Ruby also leaves the `content-length` header set to the original request's value: 
 ``` 
 require 'net/http' 

 uri = URI('https://storage.googleapis.com/justin-reid-test/test.js') 
 res = Net::HTTP.get_response(uri) 

 puts "Fetching: https://storage.googleapis.com/justin-reid-test/test.js" 
 puts "Body size using String#bytesize: #{res.body.to_s.bytesize}" 
 puts "Content-Length response header: #{res.content_length}" 
 ``` 

 Results in: 
 ``` 
 Fetching: https://storage.googleapis.com/justin-reid-test/test.js 
 Body size using String#bytesize: 9995 
 Content-Length response header: 2733 
 ``` 

 This means that an incorrect `content-length` header is passed back when net/http makes requests for gzip objects and inflates them.  


 This issue was noticed when Rack changed their behaviour in how they compute content-length. They used to compute the content-length for each body, but that changed in 2.0.8: 
 https://github.com/rack/rack/commit/8c62821f4a464858a6b6ca3c3966ec308d2bb53e#diff-10b933d2c1fdc82ceecade456c64e1c2L92 
 https://github.com/rack/rack/issues/1472#issuecomment-574362342 

 Using `Rack::ContentLength` is now the method they prefer if you need to compute the content-length. However, `Rack::ContentLength` will not try to re-compute the value if that header already exists: 
 https://github.com/rack/rack/blob/6196377654b7ff7ce7abaecea62bb285d77d53aa/lib/rack/content_length.rb#L21 

 Should Ruby: 
 - Do a `self.delete 'content-length'` in the inflater? 
 - Compute the `content-length` itself and update the header? (Hacky example: https://github.com/ruby/ruby/compare/master...jmreid:content-length) 

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