class Rack::ETag
Automatically sets the ETag header on all String bodies.
The ETag header is skipped if ETag or Last-Modified headers are sent or if a sendfile body (body.responds_to :to_path) is given (since such cases should be handled by apache/nginx).
On initialization, you can pass two parameters: a Cache-Control directive used when Etag is absent and a directive when it is present. The first defaults to nil, while the second defaults to “max-age=0, private, must-revalidate”
Constants
- DEFAULT_CACHE_CONTROL
Public Class Methods
new(app, no_cache_control = nil, cache_control = DEFAULT_CACHE_CONTROL)
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# File lib/rack/etag.rb, line 16 def initialize(app, no_cache_control = nil, cache_control = DEFAULT_CACHE_CONTROL) @app = app @cache_control = cache_control @no_cache_control = no_cache_control end
Public Instance Methods
call(env)
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# File lib/rack/etag.rb, line 22 def call(env) status, headers, body = @app.call(env) if etag_status?(status) && etag_body?(body) && !skip_caching?(headers) digest, body = digest_body(body) headers['ETag'] = %Q("#{digest}") if digest end unless headers['Cache-Control'] if digest headers['Cache-Control'] = @cache_control if @cache_control else headers['Cache-Control'] = @no_cache_control if @no_cache_control end end [status, headers, body] end
Private Instance Methods
digest_body(body)
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# File lib/rack/etag.rb, line 56 def digest_body(body) parts = [] body.each { |part| parts << part } string_body = parts.join digest = Digest::MD5.hexdigest(string_body) unless string_body.empty? [digest, parts] end
etag_body?(body)
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# File lib/rack/etag.rb, line 47 def etag_body?(body) !body.respond_to?(:to_path) end
etag_status?(status)
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# File lib/rack/etag.rb, line 43 def etag_status?(status) status == 200 || status == 201 end
skip_caching?(headers)
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# File lib/rack/etag.rb, line 51 def skip_caching?(headers) (headers['Cache-Control'] && headers['Cache-Control'].include?('no-cache')) || headers.key?('ETag') || headers.key?('Last-Modified') end