Abstract interface for a cache. More...

#include "cache_interface.h"

Inheritance diagram for net_instaweb::CacheInterface:

Classes
class	Callback

struct	KeyCallback
	Vector of structures used to initiate a MultiGet. More...

class	SynchronousCallback

Public Types
enum	KeyState { kAvailable = 0, kNotFound = 1, kOverload = 2, kNetworkError = 3, kTimeout = 4 }

typedef std::vector< KeyCallback >	MultiGetRequest

Public Member Functions
virtual void	Get (const GoogleString &key, Callback *callback)=0

virtual void	MultiGet (MultiGetRequest *request)

virtual void	Put (const GoogleString &key, const SharedString &value)=0

virtual void	Delete (const GoogleString &key)=0

void	PutSwappingString (const GoogleString &key, GoogleString *value)

virtual GoogleString	Name () const =0

virtual CacheInterface *	Backend ()

virtual bool	IsBlocking () const =0

virtual bool	IsHealthy () const =0

virtual void	ShutDown ()=0

virtual bool	MustEncodeKeyInValueOnPut () const

virtual void	PutWithKeyInValue (const GoogleString &key, const SharedString &key_and_value)

Static Public Member Functions
static const char *	KeyStateName (KeyState state)

Protected Member Functions
void	ValidateAndReportResult (const GoogleString &key, KeyState state, Callback *callback)
	Invokes callback->ValidateCandidate() and callback->Done() as appropriate.

void	ReportMultiGetNotFound (MultiGetRequest *request)

Detailed Description

Abstract interface for a cache.

Member Enumeration Documentation

enum net_instaweb::CacheInterface::KeyState

Enumerator
kAvailable	Requested key is available for serving.
kNotFound	Requested key needs to be written.
kOverload	Lookup is discarded due to cache server is overloaded.
kNetworkError	Cache lookup ended up in network error.
kTimeout	Request timeout.

Member Function Documentation

virtual CacheInterface* net_instaweb::CacheInterface::Backend ( )

virtual

If this cache is merely a wrapper around a backend that actually does all the work, returns that backend cache object. Otherwise just returns 'this'. Used for testing.

Reimplemented in net_instaweb::CacheStats, net_instaweb::ThreadsafeCache, net_instaweb::CompressedCache, and net_instaweb::CacheKeyPrepender.

virtual void net_instaweb::CacheInterface::Get	(	const GoogleString &	key,
		Callback *	callback
	)

pure virtual

Initiates a cache fetch, calling callback->ValidateCandidate() and then callback->Done(state) when done.

Note: implementations should normally invoke the callback via ValidateAndReportResult, which will combine ValidateCandidate() and Done() together properly.

Implemented in net_instaweb::SharedMemCache< kBlockSize >, net_instaweb::RedisCache, net_instaweb::CacheBatcher, net_instaweb::AprMemCache, net_instaweb::FileCache, net_instaweb::AsyncCache, net_instaweb::DelayCache, net_instaweb::CacheStats, net_instaweb::FallbackCache, net_instaweb::ThreadsafeCache, net_instaweb::LRUCache, net_instaweb::MockTimeCache, net_instaweb::InMemoryCache, net_instaweb::WriteThroughCache, net_instaweb::CompressedCache, and net_instaweb::CacheKeyPrepender.

virtual bool net_instaweb::CacheInterface::IsBlocking ( ) const

pure virtual

Returns true if this cache is guaranteed to call its callbacks before returning from Get and MultiGet.

Implemented in net_instaweb::SharedMemCache< kBlockSize >, net_instaweb::CacheBatcher, net_instaweb::AprMemCache, net_instaweb::LRUCache, net_instaweb::RedisCache, net_instaweb::DelayCache, net_instaweb::FileCache, net_instaweb::AsyncCache, net_instaweb::MockTimeCache, net_instaweb::WriteThroughCache, net_instaweb::CacheStats, net_instaweb::FallbackCache, net_instaweb::ThreadsafeCache, net_instaweb::InMemoryCache, net_instaweb::CompressedCache, and net_instaweb::CacheKeyPrepender.

virtual bool net_instaweb::CacheInterface::IsHealthy ( ) const

pure virtual

IsHealthy() is a rough estimation of whether cache is available for any operations. If it's false, caller may reasonably expect that making calls right now is useless as they will fail or have high latency. If it's true, operations should succeed, but some still may fail occasionally. The primary goal is to avoid sending commands to 'unhealthy' caches, e.g. if cache is under heavy load, we do not want to send even more requests.

Memory and file-based caches can simply return 'true'. It should be safe to call this frequently – the implementation shouldn't do much more that check a bool flag under mutex.

Implemented in net_instaweb::SharedMemCache< kBlockSize >, net_instaweb::AprMemCache, net_instaweb::CacheBatcher, net_instaweb::LRUCache, net_instaweb::RedisCache, net_instaweb::AsyncCache, net_instaweb::DelayCache, net_instaweb::FileCache, net_instaweb::WriteThroughCache, net_instaweb::MockTimeCache, net_instaweb::FallbackCache, net_instaweb::CacheStats, net_instaweb::ThreadsafeCache, net_instaweb::InMemoryCache, net_instaweb::CompressedCache, and net_instaweb::CacheKeyPrepender.

virtual void net_instaweb::CacheInterface::MultiGet ( MultiGetRequest * request )

virtual

Gets multiple keys, calling multiple callbacks. Default implementation simply loops over all the keys and calls Get.

MultiGetRequest, declared above, is a vector of structs of keys and callbacks.

Ownership of the request is transferred to this function.

Reimplemented in net_instaweb::AprMemCache, net_instaweb::AsyncCache, net_instaweb::DelayCache, net_instaweb::FallbackCache, net_instaweb::CacheStats, and net_instaweb::CacheKeyPrepender.

virtual bool net_instaweb::CacheInterface::MustEncodeKeyInValueOnPut ( ) const

inlinevirtual

To deal with underlying cache systems (e.g. memcached) that cannot tolerate arbitrary-sized keys, we use a hash of the key and put the key in the value, using the functions in key_value_codec.h.

To do this without pointlessly copying the value bytes, we use SharedString::Append(). However, that's not thread-safe. So when making a cache Asynchronous with AsyncCache, we must do the SharedString::Append call in the thread that initiates the Put, before queuing a threaded Put.

This method indicates whether a cache implementation requires encoding the keys in the value using key_value_codec.

Reimplemented in net_instaweb::AprMemCache.

virtual GoogleString net_instaweb::CacheInterface::Name ( ) const

pure virtual

The name of this CacheInterface – used for logging and debugging.

It is strongly recommended that you provide a static GoogleString FormatName(...) method for use in formatting the Name() return, and in testing, e.g. in third_party/pagespeed/system/system_caches_test.cc.

Implemented in net_instaweb::SharedMemCache< kBlockSize >, net_instaweb::CacheBatcher, net_instaweb::AprMemCache, net_instaweb::LRUCache, net_instaweb::RedisCache, net_instaweb::DelayCache, net_instaweb::FileCache, net_instaweb::WriteThroughCache, net_instaweb::FallbackCache, net_instaweb::AsyncCache, net_instaweb::CacheStats, net_instaweb::MockTimeCache, net_instaweb::ThreadsafeCache, net_instaweb::CacheKeyPrepender, net_instaweb::InMemoryCache, and net_instaweb::CompressedCache.

virtual void net_instaweb::CacheInterface::Put	(	const GoogleString &	key,
		const SharedString &	value
	)

pure virtual

Puts a value into the cache. The value that is passed in is not modified, but the SharedString is passed by non-const pointer because its reference count is bumped.

Implemented in net_instaweb::SharedMemCache< kBlockSize >, net_instaweb::RedisCache, net_instaweb::CacheBatcher, net_instaweb::AprMemCache, net_instaweb::FileCache, net_instaweb::AsyncCache, net_instaweb::LRUCache, net_instaweb::DelayCache, net_instaweb::CacheStats, net_instaweb::FallbackCache, net_instaweb::ThreadsafeCache, net_instaweb::MockTimeCache, net_instaweb::InMemoryCache, net_instaweb::WriteThroughCache, net_instaweb::CompressedCache, and net_instaweb::CacheKeyPrepender.

void net_instaweb::CacheInterface::PutSwappingString	(	const GoogleString &	key,
		GoogleString *	value
	)

inline

Convenience method to do a Put from a GoogleString* value. The bytes will be swapped out of the value and into a temp SharedString.

virtual void net_instaweb::CacheInterface::PutWithKeyInValue	(	const GoogleString &	key,
		const SharedString &	key_and_value
	)

inlinevirtual

Performs a cache Put, but assumes the key has already been encoded into the value with key_value_codec. It is only valid to call this when MustEncodeKeyInValueOnPut() returns true.

Reimplemented in net_instaweb::AprMemCache.

void net_instaweb::CacheInterface::ReportMultiGetNotFound ( MultiGetRequest * request )

protected

Helper method to report a NotFound on each MultiGet key. Deletes the request.

virtual void net_instaweb::CacheInterface::ShutDown ( )

pure virtual

Stops all cache activity. Further Put/Delete calls will be dropped, and MultiGet/Get will call the callback with kNotFound immediately. Note there is no Enable(); once the cache is stopped it is stopped forever. This function is intended for use during process shutdown.

Implemented in net_instaweb::SharedMemCache< kBlockSize >, net_instaweb::AprMemCache, net_instaweb::CacheBatcher, net_instaweb::LRUCache, net_instaweb::RedisCache, net_instaweb::AsyncCache, net_instaweb::DelayCache, net_instaweb::FileCache, net_instaweb::WriteThroughCache, net_instaweb::FallbackCache, net_instaweb::MockTimeCache, net_instaweb::CacheStats, net_instaweb::ThreadsafeCache, net_instaweb::InMemoryCache, net_instaweb::CompressedCache, and net_instaweb::CacheKeyPrepender.

The documentation for this class was generated from the following file:

pagespeed/kernel/base/cache_interface.h

Classes

Public Types

Public Member Functions

Static Public Member Functions

Protected Member Functions

Detailed Description

Member Enumeration Documentation

Member Function Documentation