#include "async_fetch_with_lock.h"

Inheritance diagram for net_instaweb::AsyncFetchWithLock:

Public Member Functions
	AsyncFetchWithLock (const Hasher hasher, const RequestContextPtr &request_context, const GoogleString &url, const GoogleString &cache_key, NamedLockManager lock_manager, MessageHandler *message_handler)

void	Start (UrlAsyncFetcher *fetcher)

const GoogleString &	url () const
	Url to be fetched.

const GoogleString &	cache_key () const
	Cache key to be locked.

Public Member Functions inherited from net_instaweb::AsyncFetch
	AsyncFetch (const RequestContextPtr &request_ctx)

void	HeadersComplete ()

void	Done (bool success)

virtual bool	Write (const StringPiece &content, MessageHandler *handler)

virtual bool	Flush (MessageHandler *handler)

virtual bool	IsCachedResultValid (const ResponseHeaders &headers)

RequestHeaders *	request_headers ()

void	set_request_headers (RequestHeaders *headers)

void	SetRequestHeadersTakingOwnership (RequestHeaders *headers)
	Same as above, but takes ownership.

const RequestHeaders *	request_headers () const

ResponseHeaders *	response_headers ()
	See doc for request_headers and set_request_headers.

void	set_response_headers (ResponseHeaders *headers)

ResponseHeaders *	extra_response_headers ()

void	set_extra_response_headers (ResponseHeaders *headers)

virtual bool	IsBackgroundFetch () const

virtual void	Reset ()

bool	headers_complete () const

bool	content_length_known () const

int64	content_length () const

void	set_content_length (int64 x)

GoogleString	LoggingString ()

virtual const RequestContextPtr &	request_context ()

virtual AbstractLogRecord *	log_record ()

void	FixCacheControlForGoogleCache ()

Public Member Functions inherited from net_instaweb::Writer
virtual bool	Dump (Writer writer, MessageHandler message_handler)

Protected Member Functions
virtual bool	ShouldYieldToRedundantFetchInProgress ()=0

virtual void	Finalize (bool lock_failure, bool success)

virtual void	StartFetch (UrlAsyncFetcher fetcher, MessageHandler handler)=0

virtual void	HandleDone (bool success)

virtual void	HandleHeadersComplete ()

virtual bool	HandleWrite (const StringPiece &content, MessageHandler *handler)

virtual bool	HandleFlush (MessageHandler *handler)

Friends
class	RewriteContextTest

Additional Inherited Members
Static Public Member Functions inherited from net_instaweb::AsyncFetch
static bool	IsGoogleCacheVia (StringPiece via_value)

Static Public Attributes inherited from net_instaweb::AsyncFetch
static const int	kContentLengthUnknown = -1

Detailed Description

AsyncFetch object which tries to acquire lock before fetching content. Start() will returns false, if it fails to acquire lock. Note that acquiring a lock will fail if same resource is fetching somewhere else. Caller will call the Start() which will try to acquire a lock and internally call StartFetch() which actually triggers a fetch. Sequence of the events: 1) Caller calls AsyncFetchWithLock::Start(). 2) Start() will try to acquire lock. If lock is acquired successfully, AsyncFetchWithLock::StartFetch() will be called, otherwise AsyncFetchWithLock::Finalize() is called with lock_failure as true and success as false and StartFetch() returns false and async_fetch_with_lock object will be deleted. Note: StartFetch() will be called in case of lock failure only if ShouldYieldToRedundantFetchInProgress() returns false. 3) Subclass defines StartFetch() function which actually triggers UrlAsyncFetcher::Fetch(). 4) Subclass can override HandleHeadersComplete(), HandleWrite(), HandleFlush() and HandleDone() for special handling during fetch. HandleDone() also releases the lock. Note: If any of these functions is overridden, then AsyncFetchWithLock::HandleXXX should also be called. 5) Lastly AsyncFetchWithLock::Finalize() is called just before async_fetch delete itself.

Member Function Documentation

virtual void net_instaweb::AsyncFetchWithLock::Finalize	(	bool	lock_failure,
		bool	success
	)

protectedvirtual

Finalize is called either when we fail to acquire acquire a lock or at the end of request after releasing the lock.

virtual void net_instaweb::AsyncFetchWithLock::HandleDone ( bool success )

protectedvirtual

Releases the lock. If subclass overrides the function, then, it should also call AsyncFetchWithLock::HandleDone()

Implements net_instaweb::AsyncFetch.

virtual void net_instaweb::AsyncFetchWithLock::HandleHeadersComplete ( )

protectedvirtual

HandleHeadersComplete(), HandleWrite() and HandleFlush() are no-op functions and any special handling can be done in subclass and must call the superclass function before returning.

Implements net_instaweb::AsyncFetch.

virtual bool net_instaweb::AsyncFetchWithLock::ShouldYieldToRedundantFetchInProgress ( )

protectedpure virtual

If someone is already fetching this resource, should we yield to them and try again later? If so, return true. Otherwise, if we must fetch the resource regardless, return false.

void net_instaweb::AsyncFetchWithLock::Start ( UrlAsyncFetcher * fetcher )

This will first try to acquire lock and triggers fetch by calling StartFetch() if successful. calls Finalize(true, false), if it fails to acquire lock, and deletes this.

virtual void net_instaweb::AsyncFetchWithLock::StartFetch	(	UrlAsyncFetcher *	fetcher,
		MessageHandler *	handler
	)

protectedpure virtual

StartFetch() will be called after the lock is acquired. The subclass implements this function and is responsible for UrlAsyncFetcher::Fetch().

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

net/instaweb/http/public/async_fetch_with_lock.h

Public Member Functions

Protected Member Functions

Friends

Additional Inherited Members

Detailed Description

Member Function Documentation