path: root/indra/llcorehttp/_httpoperation.h

/**
 * @file _httpoperation.h
 * @brief Internal declarations for HttpOperation and sub-classes
 *
 * $LicenseInfo:firstyear=2012&license=viewerlgpl$
 * Second Life Viewer Source Code
 * Copyright (C) 2012, Linden Research, Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation;
 * version 2.1 of the License only.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
 * $/LicenseInfo$
 */

#ifndef	_LLCORE_HTTP_OPERATION_H_
#define	_LLCORE_HTTP_OPERATION_H_


#include "httpcommon.h"
#include "httprequest.h"
#include "_refcounted.h"


namespace LLCore
{

class HttpReplyQueue;
class HttpHandler;
class HttpService;

/// HttpOperation is the base class for all request/reply
/// pairs.
///
/// Operations are expected to be of two types:  immediate
/// and queued.  Immediate requests go to the singleton
/// request queue and when picked up by the worker thread
/// are executed immediately and there results placed on
/// the supplied reply queue.  Queued requests (namely for
/// HTTP operations), go to the request queue, are picked
/// up and moved to a ready queue where they're ordered by
/// priority and managed by the policy component, are
/// then activated issuing HTTP requests and moved to an
/// active list managed by the transport (libcurl) component
/// and eventually finalized when a response is available
/// and status and data return via reply queue.
///
/// To manage these transitions, derived classes implement
/// three methods:  stageFromRequest, stageFromReady and
/// stageFromActive.  Immediate requests will only override
/// stageFromRequest which will perform the operation and
/// return the result by invoking addAsReply() to put the
/// request on a reply queue.  Queued requests will involve
/// all three stage methods.
///
/// Threading:  not thread-safe.  Base and derived classes
/// provide no locking.  Instances move across threads
/// via queue-like interfaces that are thread compatible
/// and those interfaces establish the access rules.

class HttpOperation : public LLCoreInt::RefCounted
{
public:
	/// Threading:  called by a consumer/application thread.
	HttpOperation();

protected:
	/// Threading:  called by any thread.
	virtual ~HttpOperation();							// Use release()

private:
	HttpOperation(const HttpOperation &);				// Not defined
	void operator=(const HttpOperation &);				// Not defined

public:
	/// Register a reply queue and a handler for completion notifications.
	///
	/// Invokers of operations that want to receive notification that an
	/// operation has been completed do so by binding a reply queue and
	/// a handler object to the request.
	///
	/// @param	reply_queue		Pointer to the reply queue where completion
	///							notifications are to be queued (typically
	///							by addAsReply()).  This will typically be
	///							the reply queue referenced by the request
	///							object.  This method will increment the
	///							refcount on the queue holding the queue
	///							until delivery is complete.  Using a reply_queue
	///							even if the handler is NULL has some benefits
	///							for memory deallocation by keeping it in the
	///							originating thread.
	///
	/// @param	handler			Possibly NULL pointer to a non-refcounted
	////						handler object to be invoked (onCompleted)
	///							when the operation is finished.  Note that
	///							the handler object is never dereferenced
	///							by the worker thread.  This is passible data
	///							until notification is performed.
	///
	/// Threading:  called by application thread.
	///
	void setReplyPath(HttpReplyQueue * reply_queue,
					  HttpHandler * handler);

	/// The three possible staging steps in an operation's lifecycle.
	/// Asynchronous requests like HTTP operations move from the
	/// request queue to the ready queue via stageFromRequest.  Then
	/// from the ready queue to the active queue by stageFromReady.  And
	/// when complete, to the reply queue via stageFromActive and the
	/// addAsReply utility.
	///
	/// Immediate mode operations (everything else) move from the
	/// request queue to the reply queue directly via stageFromRequest
	/// and addAsReply with no existence on the ready or active queues.
	///
	/// These methods will take out a reference count on the request,
	/// caller only needs to dispose of its reference when done with
	/// the request. 
	///
	/// Threading:  called by worker thread.
	///
	virtual void stageFromRequest(HttpService *);
	virtual void stageFromReady(HttpService *);
	virtual void stageFromActive(HttpService *);

	/// Delivers a notification to a handler object on completion.
	///
	/// Once a request is complete and it has been removed from its
	/// reply queue, a handler notification may be delivered by a
	/// call to HttpRequest::update().  This method does the necessary
	/// dispatching.
	///
	/// Threading:  called by application thread.
	///
	virtual void visitNotifier(HttpRequest *);

	/// Cancels the operation whether queued or active.
	/// Final status of the request becomes canceled (an error) and
	/// that will be delivered to caller via notification scheme.
	///
	/// Threading:  called by worker thread.
	///
	virtual HttpStatus cancel();
	
protected:
	/// Delivers request to reply queue on completion.  After this
	/// call, worker thread no longer accesses the object and it
	/// is owned by the reply queue.
	///
	/// Threading:  called by worker thread.
	///
	void addAsReply();
	
protected:
	HttpReplyQueue *			mReplyQueue;			// Have refcount
	HttpHandler *				mUserHandler;			// Naked pointer

public:
	// Request Data
	HttpRequest::policy_t		mReqPolicy;
	HttpRequest::priority_t		mReqPriority;

	// Reply Data
	HttpStatus					mStatus;

	// Tracing, debug and metrics
	HttpTime					mMetricCreated;
	int							mTracing;
};  // end class HttpOperation


/// HttpOpStop requests the servicing thread to shutdown
/// operations, cease pulling requests from the request
/// queue and release shared resources (particularly
/// those shared via reference count).  The servicing
/// thread will then exit.  The underlying thread object
/// remains so that another thread can join on the
/// servicing thread prior to final cleanup.  The
/// request *does* generate a reply on the response
/// queue, if requested.

class HttpOpStop : public HttpOperation
{
public:
	HttpOpStop();

protected:
	virtual ~HttpOpStop();

private:
	HttpOpStop(const HttpOpStop &);					// Not defined
	void operator=(const HttpOpStop &);				// Not defined

public:
	virtual void stageFromRequest(HttpService *);

};  // end class HttpOpStop


/// HttpOpNull is a do-nothing operation used for testing via
/// a basic loopback pattern.  It's executed immediately by
/// the servicing thread which bounces a reply back to the
/// caller without any further delay.

class HttpOpNull : public HttpOperation
{
public:
	HttpOpNull();

protected:
	virtual ~HttpOpNull();

private:
	HttpOpNull(const HttpOpNull &);					// Not defined
	void operator=(const HttpOpNull &);				// Not defined

public:
	virtual void stageFromRequest(HttpService *);

};  // end class HttpOpNull


/// HttpOpSpin is a test-only request that puts the worker
/// thread into a cpu spin.  Used for unit tests and cleanup
/// evaluation.  You do not want to use this in production.
class HttpOpSpin : public HttpOperation
{
public:
	// 0 does a hard spin in the operation
	// 1 does a soft spin continuously requeuing itself
	HttpOpSpin(int mode);

protected:
	virtual ~HttpOpSpin();

private:
	HttpOpSpin(const HttpOpSpin &);					// Not defined
	void operator=(const HttpOpSpin &);				// Not defined

public:
	virtual void stageFromRequest(HttpService *);

protected:
	int			mMode;
};  // end class HttpOpSpin


}   // end namespace LLCore

#endif	// _LLCORE_HTTP_OPERATION_H_