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public/gcsdk/gcsqlwritequeue.h

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+//====== Copyright ©, Valve Corporation, All rights reserved. =======
+// GCSqlWriteQueue.h
+//
+// A utility class that allows for templating based upon a SQL schema type, and then
+// queuing up a number of those records to be written to SQL. This will buffer them until
+// either a certain number have been queued or a period of time has elapsed, at which point
+// it will flush them to SQL in a single transaction.
+//
+//===================================================================
+#ifndef GCSQLWRITEQUEUE_H
+#define GCSQLWRITEQUEUE_H
+
+#include "scheduledfunction.h"
+
+namespace GCSDK
+{
+
+class CGCBase;
+
+template < typename TSqlClass >
+class CGCSQLWriteQueue
+{
+public:
+
+	CGCSQLWriteQueue( uint32 nMaxToCache, uint32 nMaxMSToWrite ) :
+		m_nMaxToCache( nMaxToCache ),
+		m_nMaxMSToWrite( nMaxMSToWrite )
+	{
+		m_QueuedRecords.EnsureCapacity( nMaxToCache );
+	}
+	
+	//called to queue the record for writing, which will occur either when the maximum time between writebacks has occurred, or
+	//when the cache has filled up
+	void QueueRecord( const TSqlClass& sch )
+	{
+		m_QueuedRecords.AddToTail( sch );
+
+		//now handle either dispatching, or scheduling a timeout dispatch
+		if( ( uint32 )m_QueuedRecords.Count() >= m_nMaxToCache )
+		{
+			//unschedule first. This way if while we are yielded, we add another entry, it can schedule a new timeout
+			m_TimeCommit.Cancel();
+			CreateJobToCommitSQL();
+		}
+		else if( !m_TimeCommit.BIsScheduled() )
+		{
+			m_TimeCommit.Schedule( this, &CGCSQLWriteQueue< TSqlClass >::CreateJobToCommitSQL, m_nMaxMSToWrite );			
+		}
+	}
+
+	//a yielding version of the above function
+	void YieldingQueueRecord( const TSqlClass& sch )
+	{
+		m_QueuedRecords.AddToTail( sch );
+
+		//now handle either dispatching, or scheduling a timeout dispatch
+		if( ( uint32 )m_QueuedRecords.Count() >= m_nMaxToCache )
+		{
+			//unschedule first. This way if while we are yielded, we add another entry, it can schedule a new timeout
+			m_TimeCommit.Cancel();
+			YieldingFlushQueuedViewsToSQL();
+		}
+		else if( !m_TimeCommit.BIsScheduled() )
+		{
+			m_TimeCommit.Schedule( this, &CGCSQLWriteQueue< TSqlClass >::CreateJobToCommitSQL, m_nMaxMSToWrite );			
+		}
+	}
+	
+private:
+
+	//called internally when we kick off a job after N amount of time has expired
+	template < typename TSqlClass >
+	class CTimeExpiredCommitJob : public CGCJob
+	{
+	public:
+		CTimeExpiredCommitJob( CGCBase* pGC, CGCSQLWriteQueue< TSqlClass >* pClass ) : CGCJob( pGC ), m_pClass( pClass )	{}
+		virtual bool BYieldingRunJob( void* pvStartParm )
+		{
+			m_pClass->YieldingFlushQueuedViewsToSQL();
+			return true;
+		}
+	private:
+		CGCSQLWriteQueue< TSqlClass >*	m_pClass;
+	};
+
+	//the function called when time expires to start a job and commit the requests to SQL
+	void CreateJobToCommitSQL()
+	{
+		//kick off our job, which just calls the flush
+		CGCJob* pJob = new CTimeExpiredCommitJob< TSqlClass >( GGCBase(), this );
+		pJob->StartJobDelayed( NULL );
+	}
+
+	//handles committing the list of queued views to SQL
+	void YieldingFlushQueuedViewsToSQL()
+	{
+		if( m_QueuedRecords.Count() == 0 )
+			return;
+
+		//move the contents into a local vector so we don't have any conflicts of global state
+		CUtlVector< TSqlClass > localQueue;
+		localQueue.Swap( m_QueuedRecords );
+		//prepare the queue for the next batch (so we don't have intermediate resizes)
+		m_QueuedRecords.EnsureCapacity( m_nMaxToCache );
+
+		// start a transaction for all this work
+		CSQLAccess sqlAccess;
+		sqlAccess.BBeginTransaction( "CGCWatchDownloadedReplayJob::FlushQueuedViewsToSQL" );
+
+		FOR_EACH_VEC( localQueue, nCurrView )
+		{
+			sqlAccess.BYieldingInsertRecord( &localQueue[ nCurrView ] );
+		}
+
+		sqlAccess.BCommitTransaction();
+	}
+
+	//the records that we have queued
+	CUtlVector< TSqlClass >									m_QueuedRecords;
+	//schedules a write back to ensure we commit at least every N seconds
+	CScheduledFunction< CGCSQLWriteQueue< TSqlClass > >		m_TimeCommit;
+	//maximum number of seconds between commits
+	uint32													m_nMaxMSToWrite;
+	//maximum number of records to buffer before writing back
+	uint32													m_nMaxToCache;
+};
+
+} //namespace GCSDK
+
+#endif
+