feat: impl bitcoin-core's gettxspendingprevout and getmempooldescendants RPCs (#759 part 1)

docker-compose.signer.yml

@@ -39,7 +39,7 @@ services:
 
   bitcoind:
     container_name: sbtc-bitcoind
-    image: lncm/bitcoind:v25.1
+    image: lncm/bitcoind:v27.0
     volumes:
       - ./signer/tests/service-configs/bitcoin.conf:/data/.bitcoin/bitcoin.conf:ro
     restart: on-failure

docker/docker-compose.ci.yml

@@ -1,7 +1,7 @@
 services:
 
   bitcoind:
-    image: lncm/bitcoind:v25.0
+    image: lncm/bitcoind:v27.0
     volumes:
       - ../signer/tests/service-configs/bitcoin.conf:/data/.bitcoin/bitcoin.conf:ro
     restart: on-failure

docker/docker-compose.test.yml

@@ -2,7 +2,7 @@ services:
 
   bitcoind:
     container_name: bitcoind
-    image: lncm/bitcoind:v25.0
+    image: lncm/bitcoind:v27.0
     volumes:
       - ../signer/tests/service-configs/bitcoin.conf:/data/.bitcoin/bitcoin.conf:ro
     restart: on-failure

signer/src/bitcoin/client.rs

@@ -72,4 +72,17 @@ impl BitcoinInteract for ApiFallbackClient<BitcoinCoreClient> {
         self.exec(|client, _| client.broadcast_transaction(tx))
             .await
     }
+
+    async fn find_mempool_transactions_spending_output(
+        &self,
+        outpoint: &bitcoin::OutPoint,
+    ) -> Result<Vec<Txid>, Error> {
+        self.exec(|client, _| client.find_mempool_transactions_spending_output(outpoint))
+            .await
+    }
+
+    async fn find_mempool_descendants(&self, txid: &Txid) -> Result<Vec<Txid>, Error> {
+        self.exec(|client, _| client.find_mempool_descendants(txid))
+            .await
+    }
 }

signer/src/bitcoin/mod.rs

@@ -49,4 +49,37 @@ pub trait BitcoinInteract: Sync + Send {
         &self,
         tx: &bitcoin::Transaction,
     ) -> impl Future<Output = Result<(), Error>> + Send;
+
+    /// Find transactions in the mempool which spend the given output. `txid`
+    /// must be a known confirmed transaction.
+    ///
+    /// This method returns an (unordered) list of transaction IDs which are in
+    /// the mempool and spend the given (confirmed) output.
+    ///
+    /// If there are no transactions in the mempool which spend the given
+    /// output, an empty list is returned.
+    fn find_mempool_transactions_spending_output(
+        &self,
+        outpoint: &bitcoin::OutPoint,
+    ) -> impl Future<Output = Result<Vec<Txid>, Error>> + Send;
+
+    /// Finds all transactions in the mempool which are descendants of the given
+    /// mempool transaction. `txid` must be a transaction in the mempool.
+    ///
+    /// This method returns an (unordered) list of transaction IDs which are
+    /// both direct and indirect descendants of the given transaction, meaning
+    /// that they either directly spend an output of the given transaction or
+    /// spend an output of a transaction which is itself a descendant of the
+    /// given transaction.
+    ///
+    /// If there are no descendants of the given transaction in the mempool, an
+    /// empty list is returned.
+    ///
+    /// Use [`Self::find_mempool_transactions_spending_output`] to find
+    /// transactions in the mempool which spend an output of a confirmed
+    /// transaction if needed prior to calling this method.
+    fn find_mempool_descendants(
+        &self,
+        txid: &Txid,
+    ) -> impl Future<Output = Result<Vec<Txid>, Error>> + Send;
 }

signer/src/bitcoin/rpc.rs

@@ -6,6 +6,7 @@ use bitcoin::Amount;
 use bitcoin::Block;
 use bitcoin::BlockHash;
 use bitcoin::Denomination;
+use bitcoin::OutPoint;
 use bitcoin::ScriptBuf;
 use bitcoin::Transaction;
 use bitcoin::Txid;
@@ -124,6 +125,47 @@ pub struct BitcoinTxInfo {
     pub block_time: u64,
 }
 
+/// A struct containing the response from bitcoin-core for a
+/// `gettxspendingprevout` RPC call. The actual response is an array; this
+/// struct represents a single element of that array.
+///
+/// # Notes
+///
+/// * This endpoint requires bitcoin-core v27.0 or later.
+/// * Documentation for this endpoint can be found at
+///   https://bitcoincore.org/en/doc/27.0.0/rpc/blockchain/gettxspendingprevout/
+/// * This struct omits some fields returned from bitcoin-core: `txid` and
+///   `vout`, which are just the txid and vout of the outpoint which was passed
+///   as RPC arguments. We don't need them because we're not providing multiple
+///   outpoints to check, so we don't need to map the results back to specific
+///   outpoints.
+#[derive(Clone, PartialEq, Eq, Debug, serde::Deserialize, serde::Serialize)]
+pub struct TxSpendingPrevOut {
+    /// The txid of the transaction which spent the output.
+    #[serde(rename = "spendingtxid")]
+    pub spending_txid: Option<Txid>,
+}
+
+/// A struct representing an output of a transaction. This is necessary as
+/// the [`bitcoin::OutPoint`] type does not serialize to the format that the
+/// bitcoin-core RPC expects.
+#[derive(Clone, PartialEq, Eq, Debug, serde::Deserialize, serde::Serialize)]
+pub struct RpcOutPoint {
+    /// The txid of the transaction including the output.
+    pub txid: Txid,
+    /// The index of the output in the transaction.
+    pub vout: u32,
+}
+
+impl From<&OutPoint> for RpcOutPoint {
+    fn from(outpoint: &OutPoint) -> Self {
+        Self {
+            txid: outpoint.txid,
+            vout: outpoint.vout,
+        }
+    }
+}
+
 /// A description of an input into a transaction.
 #[derive(Clone, PartialEq, Eq, Debug, serde::Deserialize, serde::Serialize)]
 pub struct BitcoinTxVin {
@@ -299,6 +341,69 @@ impl BitcoinCoreClient {
         }
     }
 
+    /// Scan the Bitcoin node's mempool to find transactions spending the
+    /// provided output. This method uses the `gettxspendingprevout` RPC
+    /// endpoint.
+    ///
+    /// # Notes
+    ///
+    /// This method requires bitcoin-core v27 or later.
+    pub fn get_tx_spending_prevout(&self, outpoint: &OutPoint) -> Result<Vec<Txid>, Error> {
+        let rpc_outpoint = RpcOutPoint::from(outpoint);
+        let args = [serde_json::to_value(vec![rpc_outpoint]).map_err(Error::JsonSerialize)?];
+
+        let response = self
+            .inner
+            .call::<Vec<TxSpendingPrevOut>>("gettxspendingprevout", &args);
+
+        let results = match response {
+            Ok(response) => Ok(response),
+            Err(err) => Err(Error::BitcoinCoreGetTxSpendingPrevout(err, *outpoint)),
+        }?;
+
+        // We will get results for each outpoint we pass in, and if there is no
+        // transaction spending the outpoint then the `spending_txid` field will
+        // be `None`. We filter out the `None`s and collect the `Some`s into a
+        // vector of `Txid`s.
+        let txids = results
+            .into_iter()
+            .filter_map(|result| result.spending_txid)
+            .collect::<Vec<_>>();
+
+        Ok(txids)
+    }
+
+    /// Scan the Bitcoin node's mempool to find transactions that are
+    /// descendants of the provided transaction. This method uses the
+    /// `getmempooldescendants` RPC endpoint.
+    ///
+    /// If the transaction is not in the mempool then an empty vector is
+    /// returned.
+    ///
+    /// If there is a chain of transactions in the mempool which implicitly
+    /// depend on the provided transaction, then the entire chain of
+    /// transactions is returned, not just the immediate descendants.
+    ///
+    /// The ordering of the transactions in the returned vector is not
+    /// guaranteed to be in any particular order.
+    ///
+    /// # Notes
+    ///
+    /// - This method requires bitcoin-core v27 or later.
+    /// - The RPC endpoint does not in itself return raw transaction data, so
+    ///   [`Self::get_tx`] must be used to fetch each transaction separately.
+    pub fn get_mempool_descendants(&self, txid: &Txid) -> Result<Vec<Txid>, Error> {
+        let args = [serde_json::to_value(txid).map_err(Error::JsonSerialize)?];
+
+        let result = self.inner.call::<Vec<Txid>>("getmempooldescendants", &args);
+
+        match result {
+            Ok(txids) => Ok(txids),
+            Err(BtcRpcError::JsonRpc(JsonRpcError::Rpc(RpcError { code: -5, .. }))) => Ok(vec![]),
+            Err(err) => Err(Error::BitcoinCoreGetMempoolDescendants(err, *txid)),
+        }
+    }
+
     /// Estimates the approximate fee in sats per vbyte needed for a
     /// transaction to be confirmed within `num_blocks`.
     ///
@@ -369,4 +474,15 @@ impl BitcoinInteract for BitcoinCoreClient {
         self.estimate_fee_rate(1)
             .map(|estimate| estimate.sats_per_vbyte)
     }
+
+    async fn find_mempool_transactions_spending_output(
+        &self,
+        outpoint: &OutPoint,
+    ) -> Result<Vec<Txid>, Error> {
+        self.get_tx_spending_prevout(outpoint)
+    }
+
+    async fn find_mempool_descendants(&self, txid: &Txid) -> Result<Vec<Txid>, Error> {
+        self.get_mempool_descendants(txid)
+    }
 }

signer/src/error.rs

@@ -25,6 +25,14 @@ pub enum Error {
     #[error("sweep transaction not found: {0}")]
     MissingSweepTransaction(bitcoin::Txid),
 
+    /// Received an error in response to getmempooldescendants RPC call
+    #[error("bitcoin-core getmempooldescendants error for txid {1}: {0}")]
+    BitcoinCoreGetMempoolDescendants(bitcoincore_rpc::Error, bitcoin::Txid),
+
+    /// Received an error in response to gettxspendingprevout RPC call
+    #[error("bitcoin-core gettxspendingprevout error for outpoint: {0}")]
+    BitcoinCoreGetTxSpendingPrevout(#[source] bitcoincore_rpc::Error, bitcoin::OutPoint),
+
     /// The nakamoto start height could not be determined.
     #[error("nakamoto start height could not be determined")]
     MissingNakamotoStartHeight,

signer/src/testing/block_observer.rs

@@ -228,6 +228,17 @@ impl BitcoinInteract for TestHarness {
     async fn broadcast_transaction(&self, _tx: &bitcoin::Transaction) -> Result<(), Error> {
         unimplemented!()
     }
+
+    async fn find_mempool_transactions_spending_output(
+        &self,
+        _outpoint: &bitcoin::OutPoint,
+    ) -> Result<Vec<Txid>, Error> {
+        unimplemented!()
+    }
+
+    async fn find_mempool_descendants(&self, _txid: &Txid) -> Result<Vec<Txid>, Error> {
+        unimplemented!()
+    }
 }
 
 impl StacksInteract for TestHarness {

signer/src/testing/context.rs

@@ -319,6 +319,17 @@ impl BitcoinInteract for WrappedMock<MockBitcoinInteract> {
     async fn broadcast_transaction(&self, tx: &bitcoin::Transaction) -> Result<(), Error> {
         self.inner.lock().await.broadcast_transaction(tx).await
     }
+
+    async fn find_mempool_transactions_spending_output(
+        &self,
+        _outpoint: &bitcoin::OutPoint,
+    ) -> Result<Vec<Txid>, Error> {
+        unimplemented!()
+    }
+
+    async fn find_mempool_descendants(&self, _txid: &Txid) -> Result<Vec<Txid>, Error> {
+        unimplemented!()
+    }
 }
 
 impl StacksInteract for WrappedMock<MockStacksInteract> {