Fix some cases where the acquire engine can stall.

src/cpp/ripple/Ledger.cpp

@@ -1176,8 +1176,13 @@ void Ledger::pendSave(bool fromConsensus)
 
 void Ledger::decPendingSaves()
 {
-	boost::recursive_mutex::scoped_lock sl(sPendingSaveLock);
-	--sPendingSaves;
+	{
+		boost::recursive_mutex::scoped_lock sl(sPendingSaveLock);
+		--sPendingSaves;
+		if (sPendingSaves != 0)
+			return;
+	}
+	theApp->getLedgerMaster().resumeAcquiring();
 }
 
 void Ledger::ownerDirDescriber(SLE::ref sle, const uint160& owner)

src/cpp/ripple/LedgerAcquire.cpp

@@ -124,7 +124,10 @@ void LedgerAcquire::onTimer(bool progress)
 	else if (!progress)
 	{
 		if (!getPeerCount())
+		{
 			addPeers();
+			resetTimer();
+		}
 		else
 			trigger(Peer::pointer(), true);
 	}

src/cpp/ripple/LedgerMaster.cpp

@@ -171,8 +171,46 @@ static bool shouldAcquire(uint32 currentLedger, uint32 ledgerHistory, uint32 can
 	return ret;
 }
 
+void LedgerMaster::resumeAcquiring()
+{
+	boost::recursive_mutex::scoped_lock ml(mLock);
+	if (!mTooFast)
+		return;
+	mTooFast = false;
+
+	if (mMissingLedger && (mMissingLedger->isComplete() || mMissingLedger->isFailed()))
+		mMissingLedger.reset();
+
+	if (mMissingLedger || !theConfig.LEDGER_HISTORY)
+	{
+		tLog(mMissingLedger, lsDEBUG) << "Fetch already in progress, not resuming";
+		return;
+	}
+
+	uint32 prevMissing = mCompleteLedgers.prevMissing(mFinalizedLedger->getLedgerSeq());
+	if (prevMissing == RangeSet::RangeSetAbsent)
+	{
+		cLog(lsDEBUG) << "no prior missing ledger, not resuming";
+		return;
+	}
+	if (shouldAcquire(mCurrentLedger->getLedgerSeq(), theConfig.LEDGER_HISTORY, prevMissing))
+	{
+		cLog(lsINFO) << "Resuming at " << prevMissing;
+		assert(!mCompleteLedgers.hasValue(prevMissing));
+		Ledger::pointer nextLedger = getLedgerBySeq(prevMissing + 1);
+		if (nextLedger)
+			acquireMissingLedger(nextLedger->getParentHash(), nextLedger->getLedgerSeq() - 1);
+		else
+		{
+			mCompleteLedgers.clearValue(prevMissing);
+			cLog(lsWARNING) << "We have a gap at: " << prevMissing + 1;
+		}
+	}
+}
+
 void LedgerMaster::setFullLedger(Ledger::ref ledger)
 { // A new ledger has been accepted as part of the trusted chain
+	cLog(lsDEBUG) << "Ledger " << ledger->getLedgerSeq() << " accepted :" << ledger->getHash();
 
 	boost::recursive_mutex::scoped_lock ml(mLock);
 
@@ -197,10 +235,14 @@ void LedgerMaster::setFullLedger(Ledger::ref ledger)
 		mMissingLedger.reset();
 
 	if (mMissingLedger || !theConfig.LEDGER_HISTORY)
-		return;
-
-	if (Ledger::getPendingSaves() > 3)
 	{
+		tLog(mMissingLedger, lsDEBUG) << "Fetch already in progress, " << mMissingLedger->getTimeouts() << " timeouts";
+		return;
+	}
+
+	if (Ledger::getPendingSaves() > 2)
+	{
+		mTooFast = true;
 		cLog(lsINFO) << "Too many pending ledger saves";
 		return;
 	}
@@ -217,10 +259,14 @@ void LedgerMaster::setFullLedger(Ledger::ref ledger)
 	{
 		uint32 prevMissing = mCompleteLedgers.prevMissing(ledger->getLedgerSeq());
 		if (prevMissing == RangeSet::RangeSetAbsent)
+		{
+			cLog(lsDEBUG) << "no prior missing ledger";
 			return;
+		}
+		cLog(lsTRACE) << "Ledger " << prevMissing << " is missing";
 		if (shouldAcquire(mCurrentLedger->getLedgerSeq(), theConfig.LEDGER_HISTORY, prevMissing))
 		{
-			cLog(lsINFO) << "Ledger " << prevMissing << " is missing";
+			cLog(lsINFO) << "Ledger " << prevMissing << " is needed";
 			assert(!mCompleteLedgers.hasValue(prevMissing));
 			Ledger::pointer nextLedger = getLedgerBySeq(prevMissing + 1);
 			if (nextLedger)

src/cpp/ripple/LedgerMaster.h

@@ -31,6 +31,7 @@ class LedgerMaster
 	RangeSet mCompleteLedgers;
 	LedgerAcquire::pointer mMissingLedger;
 	uint32 mMissingSeq;
+	bool mTooFast;	// We are acquiring faster than we're writing
 
 	void applyFutureTransactions(uint32 ledgerIndex);
 	bool isValidTransaction(const Transaction::pointer& trans);
@@ -41,7 +42,7 @@ class LedgerMaster
 
 public:
 
-	LedgerMaster() : mHeldTransactions(uint256()), mMissingSeq(0)	{ ; }
+	LedgerMaster() : mHeldTransactions(uint256()), mMissingSeq(0), mTooFast(false)	{ ; }
 
 	uint32 getCurrentLedgerIndex();
 
@@ -95,6 +96,8 @@ public:
 
 	bool haveLedgerRange(uint32 from, uint32 to);
 
+	void resumeAcquiring();
+
 	void sweep(void) { mLedgerHistory.sweep(); }
 };