Enum zebra_node_services::mempool::Request

pub enum Request {
    TransactionIds,
    TransactionsById(HashSet<UnminedTxId>),
    TransactionsByMinedId(HashSet<Hash>),
    AwaitOutput(OutPoint),
    FullTransactions,
    RejectedTransactionIds(HashSet<UnminedTxId>),
    Queue(Vec<Gossip>),
    CheckForVerifiedTransactions,
}

A mempool service request.

Requests can query the current set of mempool transactions, queue transactions to be downloaded and verified, or run the mempool to check for newly verified transactions.

Requests can’t modify the mempool directly, because all mempool transactions must be verified.

Variants

TransactionIds

Query all UnminedTxIds in the mempool.

TransactionsById(HashSet<UnminedTxId>)

Query matching UnminedTx in the mempool, using a unique set of UnminedTxIds.

TransactionsByMinedId(HashSet<Hash>)

Query matching UnminedTx in the mempool, using a unique set of transaction::Hashes. Pre-V5 transactions are matched directly; V5 transaction are matched just by the Hash, disregarding the AuthDigest.

AwaitOutput(OutPoint)

Request a transparent::Output identified by the given OutPoint, waiting until it becomes available if it is unknown.

This request is purely informational, and there are no guarantees about whether the UTXO remains unspent or is on the best chain, or any chain. Its purpose is to allow orphaned mempool transaction verification.

Correctness

Output requests should be wrapped in a timeout, so that out-of-order and invalid requests do not hang indefinitely.

Outdated requests are pruned on a regular basis.

FullTransactions

Get all the VerifiedUnminedTx in the mempool.

Equivalent to TransactionsById(TransactionIds), but each transaction also includes the miner_fee and legacy_sigop_count fields.

RejectedTransactionIds(HashSet<UnminedTxId>)

Query matching cached rejected transaction IDs in the mempool, using a unique set of UnminedTxIds.

Queue(Vec<Gossip>)

Queue a list of gossiped transactions or transaction IDs, or crawled transaction IDs.

The transaction downloader checks for duplicates across IDs and transactions.

CheckForVerifiedTransactions

Check for newly verified transactions.

The transaction downloader does not push transactions into the mempool. So a task should send this request regularly (every 5-10 seconds).

These checks also happen for other request variants, but we can’t rely on peers to send queries regularly, and crawler queue requests depend on peer responses. Also, crawler requests aren’t frequent enough for transaction propagation.

Correctness

This request is required to avoid hangs in the mempool.

The queue checker task can’t call poll_ready directly on the mempool service, because the service is wrapped in a Buffer. Calling Buffer::poll_ready reserves a buffer slot, which can cause hangs when too many slots are reserved but unused: https://docs.rs/tower/0.4.10/tower/buffer/struct.Buffer.html#a-note-on-choosing-a-bound

Trait Implementations

impl Debug for Request

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq for Request

fn eq(&self, other: &Request) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Eq for Request

impl StructuralPartialEq for Request