mempool

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 Go to latest Published: Oct 16, 2019 License: ISC Imports: 16 Imported by: 0

README

mempool

Build Status ISC License GoDoc

Package mempool provides a policy-enforced pool of unmined bitcoin transactions.

A key responsbility of the bitcoin network is mining user-generated 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.

One of the policy configuration options controls whether or not "standard" transactions are accepted. 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 a "standard" transaction changes over time. 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 bitcoin 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.

This package has intentionally been designed so it can be used as a standalone package for any projects needing the ability create an in-memory pool of bitcoin transactions that are not only valid by consensus rules, but also adhere to a configurable policy.

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
  • 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

Installation and Updating

$ go get -u github.com/daglabs/btcd/mempool

License

Package mempool is licensed under the copyfree ISC License.

Documentation

Overview

Package mempool provides a policy-enforced pool of unmined bitcoin transactions.

A key responsbility of the bitcoin network is mining user-generated 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.

One of the policy configuration options controls whether or not "standard" transactions are accepted. 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 a "standard" transaction changes over time. 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 bitcoin 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
  • 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 ErrorCode field.

Index

Constants

View Source 
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 satoshi 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 Satoshi/1000 bytes.
	DefaultMinRelayTxFee = util.Amount(1000)
)

Variables

This section is empty.

Functions

func ErrToRejectErr 

func ErrToRejectErr(err error) (wire.RejectCode, string)

ErrToRejectErr examines the underlying type of the error and returns a reject code and string appropriate to be sent in a wire.MsgReject message.

Types

type Config 

type Config struct {
	// Policy defines the various mempool configuration options related
	// to policy.
	Policy Policy

	// DAGParams identifies which DAG parameters the txpool is
	// associated with.
	DAGParams *dagconfig.Params

	// DAGChainHeight defines the function to use to access the block height of
	// the current best chain.
	DAGChainHeight func() uint64

	// MedianTimePast defines the function to use in order to access the
	// median time past calculated from the point-of-view of the current
	// chain tip within the best chain.
	MedianTimePast func() time.Time

	// CalcSequenceLockNoLock defines the function to use in order to generate
	// the current sequence lock for the given transaction using the passed
	// utxo set.
	CalcSequenceLockNoLock func(*util.Tx, blockdag.UTXOSet) (*blockdag.SequenceLock, error)

	// IsDeploymentActive returns true if the target deploymentID is
	// active, and false otherwise. The mempool uses this function to gauge
	// if transactions using new to be soft-forked rules should be allowed
	// into the mempool or not.
	IsDeploymentActive func(deploymentID uint32) (bool, error)

	// 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

	// DAG is the BlockDAG we want to use (mainly for UTXO checks)
	DAG *blockdag.BlockDAG
}

Config is a descriptor containing the memory pool configuration.

type NewBlockMsg 

type NewBlockMsg struct {
	AcceptedTxs []*TxDesc
	Tx          *util.Tx
}

NewBlockMsg is the type that is used in NewBlockMsg to transfer data about transaction removed and added to the mempool

type Policy 

type Policy struct {
	// MaxTxVersion is the transaction version that the mempool should
	// accept.  All transactions above this version are rejected as
	// non-standard.
	MaxTxVersion int32

	// AcceptNonStd defines whether to accept non-standard transactions. If
	// true, non-standard transactions will be accepted into the mempool.
	// Otherwise, all non-standard transactions will be rejected.
	AcceptNonStd bool

	// 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

	// MinRelayTxFee defines the minimum transaction fee in BTC/kB to be
	// considered a non-zero fee.
	MinRelayTxFee util.Amount
}

Policy houses the policy (configuration parameters) which is used to control the mempool.

type RuleError 

type RuleError struct {
	Err error
}

RuleError identifies a rule violation. It is used to indicate that processing of a transaction failed due to one of the many validation rules. The caller can use type assertions to determine if a failure was specifically due to a rule violation and use the Err field to access the underlying error, which will be either a TxRuleError or a blockchain.RuleError.

func (RuleError) Error 

func (e RuleError) Error() string

Error satisfies the error interface and prints human-readable errors.

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
	// contains filtered or unexported fields
}

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 

func New(cfg *Config) *TxPool

New returns a new memory pool for validating and storing standalone transactions until they are mined into a block.

func (*TxPool) CheckSpend 

func (mp *TxPool) CheckSpend(op wire.Outpoint) *util.Tx

CheckSpend checks whether the passed outpoint is already spent by a transaction in the mempool. If that's the case the spending transaction will be returned, if not nil will be returned.

func (*TxPool) Count 

func (mp *TxPool) Count() int

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) DepCount 

func (mp *TxPool) DepCount() int

DepCount returns the number of dependent transactions in the main pool. It does not include the orphan pool.

This function is safe for concurrent access.

func (*TxPool) FetchTransaction 

func (mp *TxPool) FetchTransaction(txID *daghash.TxID) (*util.Tx, error)

FetchTransaction returns the requested transaction from the transaction pool. This only fetches from the main transaction pool and does not include orphans.

This function is safe for concurrent access.

func (*TxPool) HandleNewBlock 

func (mp *TxPool) HandleNewBlock(block *util.Block, txChan chan NewBlockMsg) error

HandleNewBlock removes all the transactions in the new block from the mempool and the orphan pool, and it also removes from the mempool transactions that double spend a transaction that is already in the DAG

func (*TxPool) HaveTransaction 

func (mp *TxPool) HaveTransaction(hash *daghash.TxID) bool

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) IsInDependPool 

func (mp *TxPool) IsInDependPool(hash *daghash.TxID) bool

IsInDependPool returns whether or not the passed transaction already exists in the main pool.

This function is safe for concurrent access.

func (*TxPool) IsOrphanInPool 

func (mp *TxPool) IsOrphanInPool(hash *daghash.TxID) bool

IsOrphanInPool returns whether or not the passed transaction already exists in the orphan pool.

This function is safe for concurrent access.

func (*TxPool) IsTransactionInPool 

func (mp *TxPool) IsTransactionInPool(hash *daghash.TxID) bool

IsTransactionInPool returns whether or not the passed transaction already exists in the main pool.

This function is safe for concurrent access.

func (*TxPool) LastUpdated 

func (mp *TxPool) LastUpdated() time.Time

LastUpdated returns the last time a transaction was added to or removed from the main pool. It does not include the orphan pool.

This function is safe for concurrent access.

func (*TxPool) MaybeAcceptTransaction 

func (mp *TxPool) MaybeAcceptTransaction(tx *util.Tx, isNew bool) ([]*daghash.TxID, *TxDesc, 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, detecting orphan transactions, and insertion into the memory pool.

If the transaction is an orphan (missing parent transactions), the transaction is NOT added to the orphan pool, but each unknown referenced parent is returned. Use ProcessTransaction instead if new orphans should be added to the orphan pool.

This function is safe for concurrent access.

func (*TxPool) MiningDescs 

func (mp *TxPool) MiningDescs() []*mining.TxDesc

MiningDescs returns a slice of mining descriptors for all the transactions in the pool.

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 *util.Tx) []*TxDesc

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 *util.Tx, allowOrphan bool, tag Tag) ([]*TxDesc, 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 transaactions that were added as a result of the passed one being accepted.

This function is safe for concurrent access.

func (*TxPool) RawMempoolVerbose 

func (mp *TxPool) RawMempoolVerbose() map[string]*btcjson.GetRawMempoolVerboseResult

RawMempoolVerbose returns all of the entries in the mempool as a fully populated btcjson result.

This function is safe for concurrent access.

func (*TxPool) RemoveDoubleSpends 

func (mp *TxPool) RemoveDoubleSpends(tx *util.Tx)

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 

func (mp *TxPool) RemoveOrphan(tx *util.Tx)

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) 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 *util.Tx, removeDependants bool, restoreInputs bool) error

RemoveTransaction removes the passed transaction from the mempool. When the removeDependants flag is set, any transactions that depend on the removed transaction (that is to say, redeem outputs from it) will also be removed recursively from the mempool, as they would otherwise become orphans.

This function is safe for concurrent access.

func (*TxPool) RemoveTransactions 

func (mp *TxPool) RemoveTransactions(txs []*util.Tx) error

RemoveTransactions removes the passed transactions from the mempool.

This function is safe for concurrent access.

func (*TxPool) TxDescs 

func (mp *TxPool) TxDescs() []*TxDesc

TxDescs returns a slice of descriptors for all the transactions in the pool. The descriptors are to be treated as read only.

This function is safe for concurrent access.

func (*TxPool) TxIDs 

func (mp *TxPool) TxIDs() []*daghash.TxID

TxIDs returns a slice of IDs for all of the transactions in the memory pool.

This function is safe for concurrent access.

type TxRuleError 

type TxRuleError struct {
	RejectCode  wire.RejectCode // The code to send with reject messages
	Description string          // Human readable description of the issue
}

TxRuleError identifies a rule violation. It is used to indicate that processing of a transaction failed due to one of the many validation rules. The caller can use type assertions to determine if a failure was specifically due to a rule violation and access the ErrorCode field to ascertain the specific reason for the rule violation.

func (TxRuleError) Error 

func (e TxRuleError) Error() string

Error satisfies the error interface and prints human-readable errors.

Source Files

View all Source files

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