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Track transaction packages in CTxMemPoolEntry

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Associate with each CTxMemPoolEntry all the size/fees of descendant
mempool transactions.  Sort mempool by max(feerate of entry, feerate
of descendants).  Update statistics on-the-fly as transactions enter
or leave the mempool.

Also add ancestor and descendant limiting, so that transactions can
be rejected if the number or size of unconfirmed ancestors exceeds
a target, or if adding a transaction would cause some other mempool
entry to have too many (or too large) a set of unconfirmed in-
mempool descendants.
This commit is contained in:
Suhas Daftuar
2015-07-15 14:47:45 -04:00
committed by Suhas Daftuar
parent 34628a1807
commit 5add7a74a6
10 changed files with 993 additions and 65 deletions
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273
src/txmempool.h
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@@ -7,6 +7,7 @@
#define BITCOIN_TXMEMPOOL_H
#include <list>
#include <set>
#include "amount.h"
#include "coins.h"
@@ -34,9 +35,25 @@ inline bool AllowFree(double dPriority)
/** Fake height value used in CCoins to signify they are only in the memory pool (since 0.8) */
static const unsigned int MEMPOOL_HEIGHT = 0x7FFFFFFF;
/**
* CTxMemPool stores these:
class CTxMemPool;
/** \class CTxMemPoolEntry
*
* CTxMemPoolEntry stores data about the correponding transaction, as well
* as data about all in-mempool transactions that depend on the transaction
* ("descendant" transactions).
*
* When a new entry is added to the mempool, we update the descendant state
* (nCountWithDescendants, nSizeWithDescendants, and nFeesWithDescendants) for
* all ancestors of the newly added transaction.
*
* If updating the descendant state is skipped, we can mark the entry as
* "dirty", and set nSizeWithDescendants/nFeesWithDescendants to equal nTxSize/
* nTxFee. (This can potentially happen during a reorg, where we limit the
* amount of work we're willing to do to avoid consuming too much CPU.)
*
*/
class CTxMemPoolEntry
{
private:
@@ -45,27 +62,69 @@ private:
size_t nTxSize; //! ... and avoid recomputing tx size
size_t nModSize; //! ... and modified size for priority
size_t nUsageSize; //! ... and total memory usage
CFeeRate feeRate; //! ... and fee per kB
int64_t nTime; //! Local time when entering the mempool
double dPriority; //! Priority when entering the mempool
unsigned int nHeight; //! Chain height when entering the mempool
bool hadNoDependencies; //! Not dependent on any other txs when it entered the mempool
// Information about descendants of this transaction that are in the
// mempool; if we remove this transaction we must remove all of these
// descendants as well. if nCountWithDescendants is 0, treat this entry as
// dirty, and nSizeWithDescendants and nFeesWithDescendants will not be
// correct.
uint64_t nCountWithDescendants; //! number of descendant transactions
uint64_t nSizeWithDescendants; //! ... and size
CAmount nFeesWithDescendants; //! ... and total fees (all including us)
public:
CTxMemPoolEntry(const CTransaction& _tx, const CAmount& _nFee,
int64_t _nTime, double _dPriority, unsigned int _nHeight, bool poolHasNoInputsOf = false);
CTxMemPoolEntry();
CTxMemPoolEntry(const CTxMemPoolEntry& other);
const CTransaction& GetTx() const { return this->tx; }
double GetPriority(unsigned int currentHeight) const;
CAmount GetFee() const { return nFee; }
CFeeRate GetFeeRate() const { return feeRate; }
size_t GetTxSize() const { return nTxSize; }
int64_t GetTime() const { return nTime; }
unsigned int GetHeight() const { return nHeight; }
bool WasClearAtEntry() const { return hadNoDependencies; }
size_t DynamicMemoryUsage() const { return nUsageSize; }
// Adjusts the descendant state, if this entry is not dirty.
void UpdateState(int64_t modifySize, CAmount modifyFee, int64_t modifyCount);
/** We can set the entry to be dirty if doing the full calculation of in-
* mempool descendants will be too expensive, which can potentially happen
* when re-adding transactions from a block back to the mempool.
*/
void SetDirty();
bool IsDirty() const { return nCountWithDescendants == 0; }
uint64_t GetCountWithDescendants() const { return nCountWithDescendants; }
uint64_t GetSizeWithDescendants() const { return nSizeWithDescendants; }
CAmount GetFeesWithDescendants() const { return nFeesWithDescendants; }
};
// Helpers for modifying CTxMemPool::mapTx, which is a boost multi_index.
struct update_descendant_state
{
update_descendant_state(int64_t _modifySize, CAmount _modifyFee, int64_t _modifyCount) :
modifySize(_modifySize), modifyFee(_modifyFee), modifyCount(_modifyCount)
{}
void operator() (CTxMemPoolEntry &e)
{ e.UpdateState(modifySize, modifyFee, modifyCount); }
private:
int64_t modifySize;
CAmount modifyFee;
int64_t modifyCount;
};
struct set_dirty
{
void operator() (CTxMemPoolEntry &e)
{ e.SetDirty(); }
};
// extracts a TxMemPoolEntry's transaction hash
@@ -78,14 +137,49 @@ struct mempoolentry_txid
}
};
/** \class CompareTxMemPoolEntryByFee
*
* Sort an entry by max(feerate of entry's tx, feerate with all descendants).
*/
class CompareTxMemPoolEntryByFee
{
public:
bool operator()(const CTxMemPoolEntry& a, const CTxMemPoolEntry& b)
{
if (a.GetFeeRate() == b.GetFeeRate())
bool fUseADescendants = UseDescendantFeeRate(a);
bool fUseBDescendants = UseDescendantFeeRate(b);
double aFees = fUseADescendants ? a.GetFeesWithDescendants() : a.GetFee();
double aSize = fUseADescendants ? a.GetSizeWithDescendants() : a.GetTxSize();
double bFees = fUseBDescendants ? b.GetFeesWithDescendants() : b.GetFee();
double bSize = fUseBDescendants ? b.GetSizeWithDescendants() : b.GetTxSize();
// Avoid division by rewriting (a/b > c/d) as (a*d > c*b).
double f1 = aFees * bSize;
double f2 = aSize * bFees;
if (f1 == f2) {
return a.GetTime() < b.GetTime();
return a.GetFeeRate() > b.GetFeeRate();
}
return f1 > f2;
}
// Calculate which feerate to use for an entry (avoiding division).
bool UseDescendantFeeRate(const CTxMemPoolEntry &a)
{
double f1 = (double)a.GetFee() * a.GetSizeWithDescendants();
double f2 = (double)a.GetFeesWithDescendants() * a.GetTxSize();
return f2 > f1;
}
};
class CompareTxMemPoolEntryByEntryTime
{
public:
bool operator()(const CTxMemPoolEntry& a, const CTxMemPoolEntry& b)
{
return a.GetTime() < b.GetTime();
}
};
@@ -114,6 +208,71 @@ public:
* are added to the pool: if a new transaction double-spends
* an input of a transaction in the pool, it is dropped,
* as are non-standard transactions.
*
* CTxMemPool::mapTx, and CTxMemPoolEntry bookkeeping:
*
* mapTx is a boost::multi_index that sorts the mempool on 2 criteria:
* - transaction hash
* - feerate [we use max(feerate of tx, feerate of tx with all descendants)]
*
* Note: the term "descendant" refers to in-mempool transactions that depend on
* this one, while "ancestor" refers to in-mempool transactions that a given
* transaction depends on.
*
* In order for the feerate sort to remain correct, we must update transactions
* in the mempool when new descendants arrive. To facilitate this, we track
* the set of in-mempool direct parents and direct children in mapLinks. Within
* each CTxMemPoolEntry, we track the size and fees of all descendants.
*
* Usually when a new transaction is added to the mempool, it has no in-mempool
* children (because any such children would be an orphan). So in
* addUnchecked(), we:
* - update a new entry's setMemPoolParents to include all in-mempool parents
* - update the new entry's direct parents to include the new tx as a child
* - update all ancestors of the transaction to include the new tx's size/fee
*
* When a transaction is removed from the mempool, we must:
* - update all in-mempool parents to not track the tx in setMemPoolChildren
* - update all ancestors to not include the tx's size/fees in descendant state
* - update all in-mempool children to not include it as a parent
*
* These happen in UpdateForRemoveFromMempool(). (Note that when removing a
* transaction along with its descendants, we must calculate that set of
* transactions to be removed before doing the removal, or else the mempool can
* be in an inconsistent state where it's impossible to walk the ancestors of
* a transaction.)
*
* In the event of a reorg, the assumption that a newly added tx has no
* in-mempool children is false. In particular, the mempool is in an
* inconsistent state while new transactions are being added, because there may
* be descendant transactions of a tx coming from a disconnected block that are
* unreachable from just looking at transactions in the mempool (the linking
* transactions may also be in the disconnected block, waiting to be added).
* Because of this, there's not much benefit in trying to search for in-mempool
* children in addUnchecked(). Instead, in the special case of transactions
* being added from a disconnected block, we require the caller to clean up the
* state, to account for in-mempool, out-of-block descendants for all the
* in-block transactions by calling UpdateTransactionsFromBlock(). Note that
* until this is called, the mempool state is not consistent, and in particular
* mapLinks may not be correct (and therefore functions like
* CalculateMemPoolAncestors() and CalculateDescendants() that rely
* on them to walk the mempool are not generally safe to use).
*
* Computational limits:
*
* Updating all in-mempool ancestors of a newly added transaction can be slow,
* if no bound exists on how many in-mempool ancestors there may be.
* CalculateMemPoolAncestors() takes configurable limits that are designed to
* prevent these calculations from being too CPU intensive.
*
* Adding transactions from a disconnected block can be very time consuming,
* because we don't have a way to limit the number of in-mempool descendants.
* To bound CPU processing, we limit the amount of work we're willing to do
* to properly update the descendant information for a tx being added from
* a disconnected block. If we would exceed the limit, then we instead mark
* the entry as "dirty", and set the feerate for sorting purposes to be equal
* the feerate of the transaction without any descendants.
*
*/
class CTxMemPool
{
@@ -141,6 +300,31 @@ public:
mutable CCriticalSection cs;
indexed_transaction_set mapTx;
typedef indexed_transaction_set::nth_index<0>::type::iterator txiter;
struct CompareIteratorByHash {
bool operator()(const txiter &a, const txiter &b) const {
return a->GetTx().GetHash() < b->GetTx().GetHash();
}
};
typedef std::set<txiter, CompareIteratorByHash> setEntries;
private:
typedef std::map<txiter, setEntries, CompareIteratorByHash> cacheMap;
struct TxLinks {
setEntries parents;
setEntries children;
};
typedef std::map<txiter, TxLinks, CompareIteratorByHash> txlinksMap;
txlinksMap mapLinks;
const setEntries & GetMemPoolParents(txiter entry) const;
const setEntries & GetMemPoolChildren(txiter entry) const;
void UpdateParent(txiter entry, txiter parent, bool add);
void UpdateChild(txiter entry, txiter child, bool add);
public:
std::map<COutPoint, CInPoint> mapNextTx;
std::map<uint256, std::pair<double, CAmount> > mapDeltas;
@@ -156,7 +340,13 @@ public:
void check(const CCoinsViewCache *pcoins) const;
void setSanityCheck(bool _fSanityCheck) { fSanityCheck = _fSanityCheck; }
// addUnchecked must updated state for all ancestors of a given transaction,
// to track size/count of descendant transactions. First version of
// addUnchecked can be used to have it call CalculateMemPoolAncestors(), and
// then invoke the second version.
bool addUnchecked(const uint256& hash, const CTxMemPoolEntry &entry, bool fCurrentEstimate = true);
bool addUnchecked(const uint256& hash, const CTxMemPoolEntry &entry, setEntries &setAncestors, bool fCurrentEstimate = true);
void remove(const CTransaction &tx, std::list<CTransaction>& removed, bool fRecursive = false);
void removeCoinbaseSpends(const CCoinsViewCache *pcoins, unsigned int nMemPoolHeight);
void removeConflicts(const CTransaction &tx, std::list<CTransaction>& removed);
@@ -178,6 +368,33 @@ public:
void ApplyDeltas(const uint256 hash, double &dPriorityDelta, CAmount &nFeeDelta);
void ClearPrioritisation(const uint256 hash);
public:
/** Remove a set of transactions from the mempool.
* If a transaction is in this set, then all in-mempool descendants must
* also be in the set.*/
void RemoveStaged(setEntries &stage);
/** When adding transactions from a disconnected block back to the mempool,
* new mempool entries may have children in the mempool (which is generally
* not the case when otherwise adding transactions).
* UpdateTransactionsFromBlock() will find child transactions and update the
* descendant state for each transaction in hashesToUpdate (excluding any
* child transactions present in hashesToUpdate, which are already accounted
* for). Note: hashesToUpdate should be the set of transactions from the
* disconnected block that have been accepted back into the mempool.
*/
void UpdateTransactionsFromBlock(const std::vector<uint256> &hashesToUpdate);
/** Try to calculate all in-mempool ancestors of entry.
* (these are all calculated including the tx itself)
* limitAncestorCount = max number of ancestors
* limitAncestorSize = max size of ancestors
* limitDescendantCount = max number of descendants any ancestor can have
* limitDescendantSize = max size of descendants any ancestor can have
* errString = populated with error reason if any limits are hit
*/
bool CalculateMemPoolAncestors(const CTxMemPoolEntry &entry, setEntries &setAncestors, uint64_t limitAncestorCount, uint64_t limitAncestorSize, uint64_t limitDescendantCount, uint64_t limitDescendantSize, std::string &errString);
unsigned long size()
{
LOCK(cs);
@@ -209,6 +426,48 @@ public:
bool ReadFeeEstimates(CAutoFile& filein);
size_t DynamicMemoryUsage() const;
private:
/** UpdateForDescendants is used by UpdateTransactionsFromBlock to update
* the descendants for a single transaction that has been added to the
* mempool but may have child transactions in the mempool, eg during a
* chain reorg. setExclude is the set of descendant transactions in the
* mempool that must not be accounted for (because any descendants in
* setExclude were added to the mempool after the transaction being
* updated and hence their state is already reflected in the parent
* state).
*
* If updating an entry requires looking at more than maxDescendantsToVisit
* transactions, outside of the ones in setExclude, then give up.
*
* cachedDescendants will be updated with the descendants of the transaction
* being updated, so that future invocations don't need to walk the
* same transaction again, if encountered in another transaction chain.
*/
bool UpdateForDescendants(txiter updateIt,
int maxDescendantsToVisit,
cacheMap &cachedDescendants,
const std::set<uint256> &setExclude);
/** Update ancestors of hash to add/remove it as a descendant transaction. */
void UpdateAncestorsOf(bool add, txiter hash, setEntries &setAncestors);
/** For each transaction being removed, update ancestors and any direct children. */
void UpdateForRemoveFromMempool(const setEntries &entriesToRemove);
/** Sever link between specified transaction and direct children. */
void UpdateChildrenForRemoval(txiter entry);
/** Populate setDescendants with all in-mempool descendants of hash.
* Assumes that setDescendants includes all in-mempool descendants of anything
* already in it. */
void CalculateDescendants(txiter it, setEntries &setDescendants);
/** Before calling removeUnchecked for a given transaction,
* UpdateForRemoveFromMempool must be called on the entire (dependent) set
* of transactions being removed at the same time. We use each
* CTxMemPoolEntry's setMemPoolParents in order to walk ancestors of a
* given transaction that is removed, so we can't remove intermediate
* transactions in a chain before we've updated all the state for the
* removal.
*/
void removeUnchecked(txiter entry);
};
/**