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/**
* @file _httpservice.h
* @brief Declarations for internal class providing HTTP service.
*
* $LicenseInfo:firstyear=2012&license=viewerlgpl$
* 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_SERVICE_H_
#define _LLCORE_HTTP_SERVICE_H_
#include "httpcommon.h"
#include "httprequest.h"
namespace LLCoreInt
{
class HttpThread;
}
namespace LLCore
{
class HttpRequestQueue;
class HttpPolicy;
class HttpLibcurl;
/// The HttpService class does the work behind the request queue. It
/// oversees the HTTP workflow carrying out a number of tasks:
/// - Pulling requests from the global request queue
/// - Executing 'immediate' requests directly
/// - Prioritizing and re-queuing on internal queues the slower requests
/// - Providing cpu cycles to the libcurl plumbing
/// - Overseeing retry operations
///
/// Note that the service object doesn't have a pointer to any
/// reply queue. These are kept by HttpRequest and HttpOperation
/// only.
///
/// Service, Policy and Transport
///
/// HttpService could have been a monolithic class combining a request
/// queue servicer, request policy manager and network transport.
/// Instead, to prevent monolithic growth and allow for easier
/// replacement, it was developed as three separate classes: HttpService,
/// HttpPolicy and HttpLibcurl (transport). These always exist in a
/// 1:1:1 relationship with HttpService managing instances of the other
/// two. So, these classes do not use reference counting to refer
/// to one-another, their lifecycles are always managed together.
class HttpService
{
protected:
HttpService();
virtual ~HttpService();
private:
HttpService(const HttpService &); // Not defined
void operator=(const HttpService &); // Not defined
public:
enum EState
{
NOT_INITIALIZED = -1,
INITIALIZED, ///< init() has been called
RUNNING, ///< thread created and running
STOPPED ///< thread has committed to exiting
};
// Ordered enumeration of idling strategies available to
// threadRun's loop. Ordered so that std::min on values
// produces the most conservative result of multiple
// requests.
enum ELoopSpeed
{
NORMAL, ///< continuous polling of request, ready, active queues
REQUEST_SLEEP ///< can sleep indefinitely waiting for request queue write
};
static void init(HttpRequestQueue *);
static void term();
/// Threading: callable by any thread once inited.
inline static HttpService * instanceOf()
{
return sInstance;
}
/// Return the state of the worker thread. Note that the
/// transition from RUNNING to STOPPED is performed by the
/// worker thread itself. This has two weaknesses:
/// - race where the thread hasn't really stopped but will
/// - data ordering between threads where a non-worker thread
/// may see a stale RUNNING status.
///
/// This transition is generally of interest only to unit tests
/// and these weaknesses shouldn't be any real burden.
///
/// Threading: callable by any thread with above exceptions.
static EState getState()
{
return sState;
}
/// Threading: callable by any thread but uses @see getState() and
/// acquires its weaknesses.
static bool isStopped();
/// Threading: callable by application thread *once*.
void startThread();
/// Threading: callable by worker thread.
void stopRequested();
/// Threading: callable by worker thread.
void shutdown();
/// Try to find the given request handle on any of the request
/// queues and reset the priority (and queue position) of the
/// request if found.
///
/// @return True if the request was found somewhere.
///
/// Threading: callable by worker thread.
bool changePriority(HttpHandle handle, HttpRequest::priority_t priority);
HttpPolicy & getPolicy()
{
return *mPolicy;
}
HttpLibcurl & getTransport()
{
return *mTransport;
}
protected:
void threadRun(LLCoreInt::HttpThread * thread);
ELoopSpeed processRequestQueue(ELoopSpeed loop);
protected:
static HttpService * sInstance;
// === shared data ===
static volatile EState sState;
HttpRequestQueue * mRequestQueue;
volatile bool mExitRequested;
// === calling-thread-only data ===
LLCoreInt::HttpThread * mThread;
// === working-thread-only data ===
HttpPolicy * mPolicy; // Simple pointer, has ownership
HttpLibcurl * mTransport; // Simple pointer, has ownership
}; // end class HttpService
} // end namespace LLCore
#endif // _LLCORE_HTTP_SERVICE_H_
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