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”

Methods
C
N
Constants
ETAG_STRING = Rack::ETAG
 
DEFAULT_CACHE_CONTROL = "max-age=0, private, must-revalidate".freeze
 
Class Public methods
new(app, no_cache_control = nil, cache_control = DEFAULT_CACHE_CONTROL)
# File lib/rack/etag.rb, line 18
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
Instance Public methods
call(env)
# File lib/rack/etag.rb, line 24
def call(env)
  status, headers, body = @app.call(env)

  if etag_status?(status) && etag_body?(body) && !skip_caching?(headers)
    original_body = body
    digest, new_body = digest_body(body)
    body = Rack::BodyProxy.new(new_body) do
      original_body.close if original_body.respond_to?(:close)
    end
    headers[ETAG_STRING] = %Q(W/"#{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