Documentation ¶
Overview ¶
Package mempool provides a policy-enforced pool of unmined Decred transactions.
A key responsibility of the Decred network is mining transactions – regular transactions and stake transactions – into blocks. In order to facilitate this, the mining process relies on having a readily-available source of transactions to include in a block that is being solved.
At a high level, this package satisfies that requirement by providing an in-memory pool of fully validated transactions that can also optionally be further filtered based upon a configurable policy.
The Policy configuration options has flags that control whether or not "standard" transactions and old votes are accepted into the mempool. In essence, a "standard" transaction is one that satisfies a fairly strict set of requirements that are largely intended to help provide fair use of the system to all users. It is important to note that what is considered to be a "standard" transaction changes over time as policy and consensus rules evolve. For some insight, at the time of this writing, an example of _some_ of the criteria that are required for a transaction to be considered standard are that it is of the most-recently supported version, finalized, does not exceed a specific size, and only consists of specific script forms.
Since this package does not deal with other Decred specifics such as network communication and transaction relay, it returns a list of transactions that were accepted which gives the caller a high level of flexibility in how they want to proceed. Typically, this will involve things such as relaying the transactions to other peers on the network and notifying the mining process that new transactions are available.
## Feature Overview
The following is a quick overview of the major features. It is not intended to be an exhaustive list.
- Maintain a pool of fully validated transactions
- Reject non-fully-spent duplicate transactions
- Reject coinbase transactions
- Reject double spends (both from the chain and other transactions in pool)
- Reject invalid transactions according to the network consensus rules
- Full script execution and validation with signature cache support
- Individual transaction query support
- Stake transaction support (ticket purchases, votes and revocations)
- Option to accept or reject old votes
- Orphan transaction support (transactions that spend from unknown outputs)
- Configurable limits (see transaction acceptance policy)
- Automatic addition of orphan transactions that are no longer orphans as new transactions are added to the pool
- Individual orphan transaction query support
- Configurable transaction acceptance policy
- Option to accept or reject standard transactions
- Option to accept or reject transactions based on priority calculations
- Rate limiting of low-fee and free transactions
- Non-zero fee threshold
- Max signature operations per transaction
- Max orphan transaction size
- Max number of orphan transactions allowed
- Additional metadata tracking for each transaction
- Timestamp when the transaction was added to the pool
- Most recent block height when the transaction was added to the pool
- The fee the transaction pays
- The starting priority for the transaction
- Manual control of transaction removal
- Recursive removal of all dependent transactions
Errors ¶
Errors returned by this package are either the raw errors provided by underlying calls or of type mempool.RuleError. Since there are two classes of rules (mempool acceptance rules and blockchain (consensus) acceptance rules), the mempool.RuleError type contains a single Err field which will, in turn, either be a mempool.TxRuleError or a blockchain.RuleError. The first indicates a violation of mempool acceptance rules while the latter indicates a violation of consensus acceptance rules. This allows the caller to easily differentiate between unexpected errors, such as database errors, versus errors due to rule violations through type assertions. In addition, callers can programmatically determine the specific rule violation by type asserting the Err field to one of the aforementioned types and examining their underlying ErrorKind field.
Index ¶
- Constants
- func UseLogger(logger slog.Logger)
- type Config
- type ErrorKind
- type Policy
- type RuleError
- type Tag
- type TxDesc
- type TxPool
- func (mp *TxPool) Count() int
- func (mp *TxPool) FetchTransaction(txHash *chainhash.Hash) (*dcrutil.Tx, error)
- func (mp *TxPool) HaveAllTransactions(hashes []chainhash.Hash) bool
- func (mp *TxPool) HaveTransaction(hash *chainhash.Hash) bool
- func (mp *TxPool) HaveTransactions(hashes []*chainhash.Hash) []bool
- func (mp *TxPool) IsOrphanInPool(hash *chainhash.Hash) bool
- func (mp *TxPool) IsRegTxTreeKnownDisapproved(hash *chainhash.Hash) bool
- func (mp *TxPool) IsTransactionInPool(hash *chainhash.Hash) bool
- func (mp *TxPool) LastUpdated() time.Time
- func (mp *TxPool) MaybeAcceptDependents(tx *dcrutil.Tx, isTreasuryEnabled, isAutoRevocationsEnabled bool) []*dcrutil.Tx
- func (mp *TxPool) MaybeAcceptTransaction(tx *dcrutil.Tx, isNew, rateLimit bool) ([]*chainhash.Hash, error)
- func (mp *TxPool) MiningView() *mining.TxMiningView
- func (mp *TxPool) ProcessOrphans(acceptedTx *dcrutil.Tx, checkTxFlags blockchain.AgendaFlags) []*dcrutil.Tx
- func (mp *TxPool) ProcessTransaction(tx *dcrutil.Tx, allowOrphan, rateLimit, allowHighFees bool, tag Tag) ([]*dcrutil.Tx, error)
- func (mp *TxPool) PruneExpiredTx()
- func (mp *TxPool) PruneStakeTx(requiredStakeDifficulty, height int64)
- func (mp *TxPool) RemoveDoubleSpends(tx *dcrutil.Tx, isTreasuryEnabled, isAutoRevocationsEnabled bool)
- func (mp *TxPool) RemoveOrphan(tx *dcrutil.Tx, isTreasuryEnabled, isAutoRevocationsEnabled bool)
- func (mp *TxPool) RemoveOrphansByTag(tag Tag, isTreasuryEnabled, isAutoRevocationsEnabled bool) uint64
- func (mp *TxPool) RemoveTransaction(tx *dcrutil.Tx, ...)
- func (mp *TxPool) TSpendHashes() []chainhash.Hash
- func (mp *TxPool) TxDescs() []*TxDesc
- func (mp *TxPool) TxHashes() []*chainhash.Hash
- func (mp *TxPool) VerboseTxDescs() []*VerboseTxDesc
- func (mp *TxPool) VoteHashesForBlock(blockHash *chainhash.Hash) []chainhash.Hash
- func (mp *TxPool) VotesForBlocks(hashes []chainhash.Hash) [][]mining.VoteDesc
- type VerboseTxDesc
Constants ¶
const ( // ErrInvalid indicates a mempool transaction is invalid per consensus. ErrInvalid = ErrorKind("ErrInvalid") // ErrOrphanPolicyViolation indicates that an orphan block violates the // prevailing orphan policy. ErrOrphanPolicyViolation = ErrorKind("ErrOrphanPolicyViolation") // ErrMempoolDoubleSpend indicates a transaction that attempts to to spend // coins already spent by other transactions in the pool. ErrMempoolDoubleSpend = ErrorKind("ErrMempoolDoubleSpend") // ErrAlreadyVoted indicates a ticket already voted. ErrAlreadyVoted = ErrorKind("ErrorAlreadyVoted") // ErrDuplicate indicates a transaction already exists in the mempool. ErrDuplicate = ErrorKind("ErrDuplicate") // ErrCoinbase indicates a transaction is a standalone coinbase transaction. ErrCoinbase = ErrorKind("ErrCoinbase") // ErrExpired indicates a transaction will be expired as of the next block. ErrExpired = ErrorKind("ErrExpired") // ErrNonStandard indicates a non-standard transaction. ErrNonStandard = ErrorKind("ErrNonStandard") // ErrDustOutput indicates a transaction has one or more dust outputs. ErrDustOutput = ErrorKind("ErrDustOutput") // ErrInsufficientFee indicates a transaction cannot does not pay the minimum // fee required by the active policy. ErrInsufficientFee = ErrorKind("ErrInsufficientFee") // ErrTooManyVotes indicates the number of vote double spends exceeds the // maximum allowed. ErrTooManyVotes = ErrorKind("ErrTooManyVotes") // ErrDuplicateRevocation indicates a revocation already exists in the // mempool. ErrDuplicateRevocation = ErrorKind("ErrDuplicateRevocation") // ErrOldVote indicates a ticket votes on a block height lower than // the minimum allowed by the mempool. ErrOldVote = ErrorKind("ErrOldVote") // ErrAlreadyExists indicates a transaction already exists on the // main chain and is not fully spent. ErrAlreadyExists = ErrorKind("ErrAlreadyExists") // ErrSeqLockUnmet indicates a transaction sequence locks are not active. ErrSeqLockUnmet = ErrorKind("ErrSeqLockUnmet") // ErrInsufficientPriority indicates a non-stake transaction has a // priority lower than the minimum allowed. ErrInsufficientPriority = ErrorKind("ErrInsufficientPriority") // ErrFeeTooHigh indicates a transaction pays fees above the maximum // allowed by the active policy. ErrFeeTooHigh = ErrorKind("ErrFeeTooHigh") // ErrOrphan indicates a transaction is an orphan. ErrOrphan = ErrorKind("ErrOrphan") // ErrTooManyTSpends indicates the number of treasury spend hashes exceeds // the maximum allowed. ErrTooManyTSpends = ErrorKind("ErrTooManyTSpends") // ErrTSpendMinedOnAncestor indicates a referenced treasury spend was // already mined on an ancestor block. ErrTSpendMinedOnAncestor = ErrorKind("ErrTSpendMinedOnAncestor") // ErrTSpendInvalidExpiry indicates a treasury spend expiry is invalid. ErrTSpendInvalidExpiry = ErrorKind("ErrTSpendInvalidExpiry") )
const ( // DefaultBlockPrioritySize is the default size in bytes for high- // priority / low-fee transactions. It is used to help determine which // are allowed into the mempool and consequently affects their relay and // inclusion when generating block templates. DefaultBlockPrioritySize = 20000 // MempoolMaxConcurrentTSpends is the maximum number of TSpends that // are allowed in the mempool. The number 7 is also the amount of // physical space available for TSpend votes and thus is a hard limit. MempoolMaxConcurrentTSpends = 7 )
const ( // MaxStandardTxSize is the maximum size allowed for transactions that // are considered standard and will therefore be relayed and considered // for mining. MaxStandardTxSize = 100000 // DefaultMinRelayTxFee is the minimum fee in atoms that is required for // a transaction to be treated as free for relay and mining purposes. // It is also used to help determine if a transaction is considered dust // and as a base for calculating minimum required fees for larger // transactions. This value is in Atoms/1000 bytes. DefaultMinRelayTxFee = dcrutil.Amount(1e5) // BaseStandardVerifyFlags defines the script flags that should be used // when executing transaction scripts to enforce additional checks which // are required for the script to be considered standard regardless of // the state of any agenda votes. The full set of standard verification // flags must include these flags as well as any additional flags that // are conditionally enabled depending on the result of agenda votes. BaseStandardVerifyFlags = txscript.ScriptDiscourageUpgradableNops | txscript.ScriptVerifyCleanStack | txscript.ScriptVerifyCheckLockTimeVerify | txscript.ScriptVerifyCheckSequenceVerify | txscript.ScriptVerifySHA256 )
Variables ¶
This section is empty.
Functions ¶
Types ¶
type Config ¶
type Config struct { // Policy defines the various mempool configuration options related // to policy. Policy Policy // ChainParams identifies which chain parameters the txpool is // associated with. ChainParams *chaincfg.Params // NextStakeDifficulty defines the function to retrieve the stake // difficulty for the block after the current best block. // // This function must be safe for concurrent access. NextStakeDifficulty func() (int64, error) // FetchUtxoView defines the function to use to fetch unspent // transaction output information. FetchUtxoView func(*dcrutil.Tx, bool) (*blockchain.UtxoViewpoint, error) // BlockByHash defines the function use to fetch the block identified // by the given hash. BlockByHash func(*chainhash.Hash) (*dcrutil.Block, error) // BestHash defines the function to use to access the block hash of // the current best chain. BestHash func() *chainhash.Hash // BestHeight defines the function to use to access the block height of // the current best chain. BestHeight func() int64 // HeaderByHash returns the block header identified by the given hash or an // error if it doesn't exist. Note that this will return headers from both // the main chain and any side chains. HeaderByHash func(hash *chainhash.Hash) (wire.BlockHeader, error) // PastMedianTime defines the function to use in order to access the // median time calculated from the point-of-view of the current chain // tip within the best chain. PastMedianTime func() time.Time // CalcSequenceLock defines the function to use in order to generate // the current sequence lock for the given transaction using the passed // utxo view. CalcSequenceLock func(*dcrutil.Tx, *blockchain.UtxoViewpoint) (*blockchain.SequenceLock, error) // SubsidyCache defines a subsidy cache to use. SubsidyCache *standalone.SubsidyCache // SigCache defines a signature cache to use. SigCache *txscript.SigCache // AddrIndex defines the optional address index instance to use for // indexing the unconfirmed transactions in the memory pool. // This can be nil if the address index is not enabled. AddrIndex *indexers.AddrIndex // ExistsAddrIndex defines the optional exists address index instance // to use for indexing the unconfirmed transactions in the memory pool. // This can be nil if the address index is not enabled. ExistsAddrIndex *indexers.ExistsAddrIndex // AddTxToFeeEstimation defines an optional function to be called whenever a // new transaction is added to the mempool, which can be used to track fees // for the purposes of smart fee estimation. AddTxToFeeEstimation func(txHash *chainhash.Hash, fee, size int64, txType stake.TxType) // RemoveTxFromFeeEstimation defines an optional function to be called // whenever a transaction is removed from the mempool in order to track fee // estimation. RemoveTxFromFeeEstimation func(txHash *chainhash.Hash) // OnVoteReceived defines the function used to signal receiving a new // vote in the mempool. OnVoteReceived func(voteTx *dcrutil.Tx) // IsTreasuryAgendaActive returns if the treasury agenda is active or not. IsTreasuryAgendaActive func() (bool, error) // IsAutoRevocationsAgendaActive returns if the automatic ticket revocations // agenda is active or not. IsAutoRevocationsAgendaActive func() (bool, error) // IsSubsidySplitAgendaActive returns if the modified subsidy split agenda // is active or not. IsSubsidySplitAgendaActive func() (bool, error) // OnTSpendReceived defines the function used to signal receiving a new // tspend in the mempool. OnTSpendReceived func(voteTx *dcrutil.Tx) // TSpendMinedOnAncestor returns an error if the provided tspend has // been mined in an ancestor block. TSpendMinedOnAncestor func(tspend chainhash.Hash) error }
Config is a descriptor containing the memory pool configuration.
type ErrorKind ¶
type ErrorKind string
ErrorKind identifies a kind of error. It has full support for errors.Is and errors.As, so the caller can directly check against an error kind when determining the reason for an error.
type Policy ¶
type Policy struct { // DisableRelayPriority defines whether to relay free or low-fee // transactions that do not have enough priority to be relayed. DisableRelayPriority bool // AcceptNonStd defines whether to accept and relay non-standard // transactions to the network. If true, non-standard transactions // will be accepted into the mempool and relayed to the rest of the // network. Otherwise, all non-standard transactions will be rejected. AcceptNonStd bool // FreeTxRelayLimit defines the given amount in thousands of bytes // per minute that transactions with no fee are rate limited to. FreeTxRelayLimit float64 // MaxOrphanTxs is the maximum number of orphan transactions // that can be queued. MaxOrphanTxs int // MaxOrphanTxSize is the maximum size allowed for orphan transactions. // This helps prevent memory exhaustion attacks from sending a lot of // of big orphans. MaxOrphanTxSize int // MaxSigOpsPerTx is the maximum number of signature operations // in a single transaction we will relay or mine. It is a fraction // of the max signature operations for a block. MaxSigOpsPerTx int // MinRelayTxFee defines the minimum transaction fee in DCR/kB to be // considered a non-zero fee. MinRelayTxFee dcrutil.Amount // AllowOldVotes defines whether or not votes on old blocks will be // admitted and relayed. AllowOldVotes bool // MaxVoteAge defines the number of blocks in history from the next block // height of the best chain tip for which votes will be accepted. This only // applies when the AllowOldVotes option is false. MaxVoteAge uint16 // StandardVerifyFlags defines the function to retrieve the flags to // use for verifying scripts for the block after the current best block. // It must set the verification flags properly depending on the result // of any agendas that affect them. // // This function must be safe for concurrent access. StandardVerifyFlags func() (txscript.ScriptFlags, error) // EnableAncestorTracking controls whether the mining view tracks // transaction relationships in the mempool. EnableAncestorTracking bool }
Policy houses the policy (configuration parameters) which is used to control the mempool.
type RuleError ¶
RuleError identifies a rule violation. It is used to indicate that processing of a transaction failed due to one of the many validation rules. It has full support for errors.Is and errors.As, so the caller can ascertain the specific reason for the error by checking the underlying error, which will be either an ErrorKind or blockchain.RuleError.
type Tag ¶
type Tag uint64
Tag represents an identifier to use for tagging orphan transactions. The caller may choose any scheme it desires, however it is common to use peer IDs so that orphans can be identified by which peer first relayed them.
type TxDesc ¶
type TxDesc struct { mining.TxDesc // StartingPriority is the priority of the transaction when it was added // to the pool. StartingPriority float64 }
TxDesc is a descriptor containing a transaction in the mempool along with additional metadata.
type TxPool ¶
type TxPool struct {
// contains filtered or unexported fields
}
TxPool is used as a source of transactions that need to be mined into blocks and relayed to other peers. It is safe for concurrent access from multiple peers.
func New ¶
New returns a new memory pool for validating and storing standalone transactions until they are mined into a block.
func (*TxPool) Count ¶
Count returns the number of transactions in the main pool. It does not include the orphan pool.
This function is safe for concurrent access.
func (*TxPool) FetchTransaction ¶
FetchTransaction returns the requested transaction from the transaction pool. This only fetches from the main and stage transaction pools and does not include orphans.
This function is safe for concurrent access.
func (*TxPool) HaveAllTransactions ¶
HaveAllTransactions returns whether or not all of the passed transaction hashes exist in the mempool.
This function is safe for concurrent access.
func (*TxPool) HaveTransaction ¶
HaveTransaction returns whether or not the passed transaction already exists in the main pool or in the orphan pool.
This function is safe for concurrent access.
func (*TxPool) HaveTransactions ¶
HaveTransactions returns whether or not the passed transactions already exist in the main pool or in the orphan pool.
This function is safe for concurrent access.
func (*TxPool) IsOrphanInPool ¶
IsOrphanInPool returns whether or not the passed transaction already exists in the orphan pool.
This function is safe for concurrent access.
func (*TxPool) IsRegTxTreeKnownDisapproved ¶
IsRegTxTreeKnownDisapproved returns whether or not the regular tree of the block represented by the provided hash is known to be disapproved according to the votes currently in the memory pool.
The function is safe for concurrent access.
func (*TxPool) IsTransactionInPool ¶
IsTransactionInPool returns whether or not the passed transaction already exists in the main pool.
This function is safe for concurrent access.
func (*TxPool) LastUpdated ¶
LastUpdated returns the last time a transaction was added to or removed from the main pool. It does not include the orphan or stage pools.
This function is safe for concurrent access.
func (*TxPool) MaybeAcceptDependents ¶
func (mp *TxPool) MaybeAcceptDependents(tx *dcrutil.Tx, isTreasuryEnabled, isAutoRevocationsEnabled bool) []*dcrutil.Tx
MaybeAcceptDependents determines if there are any staged dependents of the passed transaction and potentially accepts them to the mempool.
It returns a slice of transactions added to the main pool. A nil slice means no transactions were moved from the stage pool to the main pool.
This function is safe for concurrent access.
func (*TxPool) MaybeAcceptTransaction ¶
func (mp *TxPool) MaybeAcceptTransaction(tx *dcrutil.Tx, isNew, rateLimit bool) ([]*chainhash.Hash, error)
MaybeAcceptTransaction is the main workhorse for handling insertion of new free-standing transactions into a memory pool. It includes functionality such as rejecting duplicate transactions, ensuring transactions follow all rules, orphan transaction handling, and insertion into the memory pool.
This function is safe for concurrent access.
func (*TxPool) MiningView ¶
func (mp *TxPool) MiningView() *mining.TxMiningView
MiningView returns a slice of mining descriptors for all the transactions in the pool in addition to a snapshot of the current pool's transaction relationships.
This is part of the mining.TxSource interface implementation and is safe for concurrent access as required by the interface contract.
func (*TxPool) ProcessOrphans ¶
func (mp *TxPool) ProcessOrphans(acceptedTx *dcrutil.Tx, checkTxFlags blockchain.AgendaFlags) []*dcrutil.Tx
ProcessOrphans determines if there are any orphans which depend on the passed transaction hash (it is possible that they are no longer orphans) and potentially accepts them to the memory pool. It repeats the process for the newly accepted transactions (to detect further orphans which may no longer be orphans) until there are no more.
It returns a slice of transactions added to the mempool. A nil slice means no transactions were moved from the orphan pool to the mempool.
This function is safe for concurrent access.
func (*TxPool) ProcessTransaction ¶
func (mp *TxPool) ProcessTransaction(tx *dcrutil.Tx, allowOrphan, rateLimit, allowHighFees bool, tag Tag) ([]*dcrutil.Tx, error)
ProcessTransaction is the main workhorse for handling insertion of new free-standing transactions into the memory pool. It includes functionality such as rejecting duplicate transactions, ensuring transactions follow all rules, orphan transaction handling, and insertion into the memory pool.
It returns a slice of transactions added to the mempool. When the error is nil, the list will include the passed transaction itself along with any additional orphan transactions that were added as a result of the passed one being accepted.
This function is safe for concurrent access.
func (*TxPool) PruneExpiredTx ¶
func (mp *TxPool) PruneExpiredTx()
PruneExpiredTx prunes expired transactions from the mempool that may no longer be able to be included into a block.
This function is safe for concurrent access.
func (*TxPool) PruneStakeTx ¶
PruneStakeTx is the function which is called every time a new block is processed. The idea is any outstanding SStx that hasn't been mined in a certain period of time (CoinbaseMaturity) and the submitted SStx's stake difficulty is below the current required stake difficulty should be pruned from mempool since they will never be mined. The same idea stands for SSGen and SSRtx
func (*TxPool) RemoveDoubleSpends ¶
func (mp *TxPool) RemoveDoubleSpends(tx *dcrutil.Tx, isTreasuryEnabled, isAutoRevocationsEnabled bool)
RemoveDoubleSpends removes all transactions which spend outputs spent by the passed transaction from the memory pool. Removing those transactions then leads to removing all transactions which rely on them, recursively. This is necessary when a block is connected to the main chain because the block may contain transactions which were previously unknown to the memory pool.
This function is safe for concurrent access.
func (*TxPool) RemoveOrphan ¶
RemoveOrphan removes the passed orphan transaction from the orphan pool and previous orphan index.
This function is safe for concurrent access.
func (*TxPool) RemoveOrphansByTag ¶
func (mp *TxPool) RemoveOrphansByTag(tag Tag, isTreasuryEnabled, isAutoRevocationsEnabled bool) uint64
RemoveOrphansByTag removes all orphan transactions tagged with the provided identifier.
This function is safe for concurrent access.
func (*TxPool) RemoveTransaction ¶
func (mp *TxPool) RemoveTransaction(tx *dcrutil.Tx, removeRedeemers, isTreasuryEnabled, isAutoRevocationsEnabled bool)
RemoveTransaction removes the passed transaction from the mempool. When the removeRedeemers flag is set, any transactions that redeem outputs from the removed transaction will also be removed recursively from the mempool, as they would otherwise become orphans.
This function is safe for concurrent access.
func (*TxPool) TSpendHashes ¶
TSpendHashes returns hashes of all existing tracked tspends. This function is safe for concurrent access.
func (*TxPool) TxDescs ¶
TxDescs returns a slice of descriptors for all the transactions in the pool. The descriptors must be treated as read only.
This function is safe for concurrent access.
func (*TxPool) TxHashes ¶
TxHashes returns a slice of hashes for all of the transactions in the memory pool.
This function is safe for concurrent access.
func (*TxPool) VerboseTxDescs ¶
func (mp *TxPool) VerboseTxDescs() []*VerboseTxDesc
VerboseTxDescs returns a slice of verbose descriptors for all the transactions in the pool. The descriptors must be treated as read only.
Callers should prefer working with the more efficient TxDescs unless they specifically need access to the additional details provided.
This function is safe for concurrent access.
func (*TxPool) VoteHashesForBlock ¶
VoteHashesForBlock returns the hashes for all votes on the provided block hash that are currently available in the mempool.
This function is safe for concurrent access.
type VerboseTxDesc ¶
type VerboseTxDesc struct { TxDesc // CurrentPriority is the current priority of the transaction within the // pool. CurrentPriority float64 // Depends enumerates any unconfirmed transactions in the pool used as // inputs for the transaction. Depends []*TxDesc }
VerboseTxDesc is a descriptor containing a transaction in the mempool along with additional more expensive to calculate metadata. Callers should prefer working with the more efficient TxDesc unless they specifically need access to the additional details provided.