Class: Async::HTTP::Cache::General

Inherits:
Protocol::HTTP::Middleware
  • Object
show all
Defined in:
lib/async/http/cache/general.rb

Overview

Implements a general shared cache according to www.rfc-editor.org/rfc/rfc9111

Constant Summary collapse

CACHE_CONTROL = 
"cache-control"
CONTENT_TYPE = 
"content-type"
AUTHORIZATION = 
"authorization"
"cookie"
"set-cookie"
CACHEABLE_RESPONSE_CODES =

Status codes of responses that MAY be stored by a cache or used in reply to a subsequent request.

tools.ietf.org/html/rfc2616#section-13.4

{
	200 => true, # OK
	203 => true, # Non-Authoritative Information
	300 => true, # Multiple Choices
	301 => true, # Moved Permanently
	302 => true, # Found
	404 => true, # Not Found
	410 => true  # Gone
}.freeze

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(app, store: Store.default) ⇒ General

Initialize a new cache middleware instance.



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# File 'lib/async/http/cache/general.rb', line 43

def initialize(app, store: Store.default)
	super(app)
	
	@count = 0
	
	@store = store
end

Instance Attribute Details

#count ⇒ Object (readonly)

Returns the value of attribute count.



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# File 'lib/async/http/cache/general.rb', line 51

def count
  @count
end

#store ⇒ Object (readonly)

Returns the value of attribute store.



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# File 'lib/async/http/cache/general.rb', line 52

def store
  @store
end

Instance Method Details

#cacheable_request?(request) ⇒ Boolean

Determine if a request is cacheable based on method, headers, and body.

Returns:

  • (Boolean) 


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# File 'lib/async/http/cache/general.rb', line 73

def cacheable_request?(request)
	# We don't support caching requests which have a request body:
	if request.body
		return false
	end
	
	# We can't cache upgraded requests:
	if request.protocol
		return false
	end
	
	# We only support caching GET and HEAD requests:
	unless request.method == "GET" || request.method == "HEAD"
		return false
	end
	
	if request.headers[AUTHORIZATION]
		return false
	end
	
	if request.headers[COOKIE]
		return false
	end
	
	# Otherwise, we can cache it:
	return true
end

#cacheable_response?(response) ⇒ Boolean

Determine if a response is cacheable based on status code and headers.

Returns:

  • (Boolean) 


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# File 'lib/async/http/cache/general.rb', line 123

def cacheable_response?(response)
	# At this point, we know response.status and response.headers.
	# But we don't know response.body or response.headers.trailer.
	unless CACHEABLE_RESPONSE_CODES.include?(response.status)
		Console.logger.debug(self, status: response.status) {"Cannot cache response with status code!"}
		return false
	end
	
	unless cacheable_response_headers?(response.headers)
		Console.logger.debug(self) {"Cannot cache response with uncacheable headers!"}
		return false
	end
	
	return true
end

#cacheable_response_headers?(headers) ⇒ Boolean

Check if response headers allow caching.

Returns:

  • (Boolean) 


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# File 'lib/async/http/cache/general.rb', line 104

def cacheable_response_headers?(headers)
	if cache_control = headers[CACHE_CONTROL]
		if cache_control.no_store? || cache_control.private?
			Console.logger.debug(self, cache_control: cache_control) {"Cannot cache response with cache-control header!"}
			return false
		end
	end
	
	if set_cookie = headers[SET_COOKIE]
		Console.logger.debug(self) {"Cannot cache response with set-cookie header!"}
		return false
	end
	
	return true
end

#call(request) ⇒ Object

Process an HTTP request, checking cache first and storing responses when appropriate.



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# File 'lib/async/http/cache/general.rb', line 184

def call(request)
	cache_control = request.headers[CACHE_CONTROL]
	
	unless cache_control&.no_cache?
		key = self.key(request)
		
		if response = @store.lookup(key, request)
			Console.logger.debug(self, key: key) {"Cache hit!"}
			@count += 1
			
			# Return the cached response:
			return response
		end
	end
	
	unless cache_control&.no_store?
		return wrap(key, request, super)
	end
	
	return super
end

#close ⇒ Object

Close the cache and clean up resources.



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# File 'lib/async/http/cache/general.rb', line 55

def close
	@store.close
ensure
	super
end

#key(request) ⇒ Object

Generate a cache key for the given request.



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# File 'lib/async/http/cache/general.rb', line 64

def key(request)
	@store.normalize(request)
	
	[request.authority, request.method, request.path]
end

#proceed_with_response_cache?(response) ⇒ Boolean

Semantically speaking, it is possible for trailers to result in an uncacheable response, so we need to check for that.

Returns:

  • (Boolean) 


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# File 'lib/async/http/cache/general.rb', line 140

def proceed_with_response_cache?(response)
	if response.headers.trailer?
		unless cacheable_response_headers?(response.headers)
			Console.logger.debug(self, trailer: trailer.keys) {"Cannot cache response with trailer header!"}
			return false
		end
	end
	
	return true
end

#wrap(key, request, response) ⇒ Object

Potentially wrap the response so that it updates the cache, if caching is possible.



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# File 'lib/async/http/cache/general.rb', line 152

def wrap(key, request, response)
	if request.head? and body = response.body
		unless body.empty?
			Console.logger.warn(self) {"HEAD request resulted in non-empty body!"}
			
			return response
		end
	end
	
	unless cacheable_request?(request)
		Console.logger.debug(self) {"Cannot cache request!"}
		return response
	end
	
	unless cacheable_response?(response)
		Console.logger.debug(self) {"Cannot cache response!"}
		return response
	end
	
	return Body.wrap(response) do |response, body|
		if proceed_with_response_cache?(response)
			key ||= self.key(request)
			
			Console.logger.debug(self, key: key) {"Updating miss!"}
			@store.insert(key, request, Response.new(response, body))
		end
	end
end