electrum: Implement --electrum-skip-merkle to avoid generating SPV …

…proofs entirely, even when it's possible

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## Unreleased
+
+- Electrum: Implement `--electrum-skip-merkle` to avoid generating SPV proofs entirely, even when it's possible.
+
 ## 0.1.3 - 2020-06-02
 
 - Electrum: Use dummy SPV proofs to support pruning with the  `--skipmerklecheck` option.

README.md

@@ -171,6 +171,8 @@ You can use bwt with pruning, but:
 
 2. Electrum needs to be run with `--skipmerklecheck` to tolerate missing SPV proofs for transactions in pruned blocks.
 
+If you're running Electrum with `--skipmerklecheck`, you may also configure bwt with `--electrum-skip-merkle` to save some resource by not generating SPV proofs even when it's possible.
+
 ### Real-time indexing
 
 By default, bwt will query bitcoind for new blocks/transactions every 5 seconds.

src/app.rs

@@ -61,7 +61,11 @@ impl App {
         let sync_tx = debounce_sender(sync_tx, DEBOUNCE_SEC);
 
         #[cfg(feature = "electrum")]
-        let electrum = ElectrumServer::start(config.electrum_rpc_addr(), query.clone());
+        let electrum = ElectrumServer::start(
+            config.electrum_rpc_addr(),
+            config.electrum_skip_merkle,
+            query.clone(),
+        );
 
         #[cfg(feature = "http")]
         let http = HttpServer::start(

src/config.rs

@@ -36,6 +36,7 @@ pub struct Config {
     )]
     pub verbose: usize,
 
+    // XXX this is not settable as an env var due to https://github.com/TeXitoi/structopt/issues/305
     #[structopt(
         short = "t",
         long,
@@ -155,6 +156,15 @@ pub struct Config {
     )]
     pub electrum_rpc_addr: Option<net::SocketAddr>,
 
+    // XXX this is not settable as an env var due to https://github.com/TeXitoi/structopt/issues/305
+    #[cfg(feature = "electrum")]
+    #[structopt(
+        long,
+        help = "Skip generating merkle proofs. Reduces resource usage, requires running Electrum with --skipmerklecheck",
+        display_order(41)
+    )]
+    pub electrum_skip_merkle: bool,
+
     #[cfg(feature = "http")]
     #[structopt(
         short,
@@ -163,7 +173,7 @@ pub struct Config {
         default_value = "127.0.0.1:3060",
         env,
         hide_env_values(true),
-        display_order(41)
+        display_order(45)
     )]
     pub http_server_addr: net::SocketAddr,
 
@@ -173,7 +183,7 @@ pub struct Config {
         help = "Allowed cross-origins for http api server (Access-Control-Allow-Origin)",
         env,
         hide_env_values(true),
-        display_order(42)
+        display_order(46)
     )]
     pub http_cors: Option<String>,
 

src/electrum.rs

@@ -25,6 +25,7 @@ const MAX_HEADERS: u32 = 2016;
 
 struct Connection {
     query: Arc<Query>,
+    skip_merkle: bool,
     stream: TcpStream,
     addr: SocketAddr,
     chan: SyncChannel<Message>,
@@ -35,6 +36,7 @@ struct Connection {
 impl Connection {
     pub fn new(
         query: Arc<Query>,
+        skip_merkle: bool,
         stream: TcpStream,
         addr: SocketAddr,
         subman: Arc<Mutex<SubscriptionManager>>,
@@ -43,6 +45,7 @@ impl Connection {
         let subscriber_id = subman.lock().unwrap().register(chan.sender());
         Connection {
             query,
+            skip_merkle,
             subman,
             subscriber_id,
             stream,
@@ -234,17 +237,22 @@ impl Connection {
     fn blockchain_transaction_get_merkle(&self, params: Value) -> Result<Value> {
         let (txid, height): (Txid, u32) = from_value(params)?;
 
-        let (merkle, pos) = match get_merkle_proof(&self.query, &txid, height) {
-            Ok(proof) => proof,
-            Err(e) => {
-                if let Some(BwtError::PrunedBlocks) = e.downcast_ref::<BwtError>() {
-                    // if we can't generate the spv proof due to pruning, return a dummy proof instead of an
-                    // error, which electrum will accept when run with --skipmerklecheck.
-                    (vec![], 0)
-                } else {
-                    bail!(e)
+        let (merkle, pos) = if !self.skip_merkle {
+            match get_merkle_proof(&self.query, &txid, height) {
+                Ok(proof) => proof,
+                Err(e) => {
+                    if let Some(BwtError::PrunedBlocks) = e.downcast_ref::<BwtError>() {
+                        // if we can't generate the spv proof due to pruning, return a dummy proof instead of an
+                        // error, which electrum will accept when run with --skipmerklecheck.
+                        (vec![], 0)
+                    } else {
+                        bail!(e)
+                    }
                 }
             }
+        } else {
+            // always return dummy SPV proofs when --electrum-skip-merkle is set
+            (vec![], 0)
         };
 
         Ok(json!({
@@ -507,7 +515,7 @@ impl ElectrumServer {
         chan
     }
 
-    pub fn start(addr: SocketAddr, query: Arc<Query>) -> Self {
+    pub fn start(addr: SocketAddr, skip_merkle: bool, query: Arc<Query>) -> Self {
         let notification = Channel::unbounded();
         Self {
             notification: notification.sender(),
@@ -524,7 +532,7 @@ impl ElectrumServer {
                     let subman = subman.clone();
                     children.push(spawn_thread("peer", move || {
                         info!("[{}] connected peer", addr);
-                        let conn = Connection::new(query, stream, addr, subman);
+                        let conn = Connection::new(query, skip_merkle, stream, addr, subman);
                         conn.run();
                         info!("[{}] disconnected peer", addr);
                     }));