Simplify main loop using Option<RPC>

src/app.rs

@@ -1,20 +1,29 @@
-use std::sync::Arc;
+use bitcoin::util::hash::Sha256dHash;
+use std::sync::{Arc, Mutex};
 
-use {daemon, index, store};
+use {daemon, index, signal::Waiter, store};
+
+use errors::*;
 
 pub struct App {
     store: store::DBStore,
     index: index::Index,
     daemon: daemon::Daemon,
+    tip: Mutex<Sha256dHash>,
 }
 
 impl App {
-    pub fn new(store: store::DBStore, index: index::Index, daemon: daemon::Daemon) -> Arc<App> {
-        Arc::new(App {
+    pub fn new(
+        store: store::DBStore,
+        index: index::Index,
+        daemon: daemon::Daemon,
+    ) -> Result<Arc<App>> {
+        Ok(Arc::new(App {
             store,
             index,
-            daemon,
-        })
+            daemon: daemon.reconnect()?,
+            tip: Mutex::new(Sha256dHash::default()),
+        }))
     }
 
     pub fn write_store(&self) -> &store::WriteStore {
@@ -29,4 +38,13 @@ impl App {
     pub fn daemon(&self) -> &daemon::Daemon {
         &self.daemon
     }
+
+    pub fn update(&self, signal: &Waiter) -> Result<bool> {
+        let mut tip = self.tip.lock().expect("failed to lock tip");
+        let new_block = *tip != self.daemon().getbestblockhash()?;
+        if new_block {
+            *tip = self.index().update(self.write_store(), &signal)?;
+        }
+        Ok(new_block)
+    }
 }

src/bin/electrs.rs

@@ -25,23 +25,22 @@ fn run_server(config: &Config) -> Result<()> {
     )?;
     // Perform initial indexing from local blk*.dat block files.
     let store = bulk::index(&daemon, &metrics, DBStore::open(&config.db_path))?;
-    let daemon = daemon.reconnect()?;
     let index = Index::load(&store, &daemon, &metrics)?;
-    let app = App::new(store, index, daemon);
-    let mut tip = app.index().update(app.write_store(), &signal)?;
-
+    let app = App::new(store, index, daemon)?;
     let query = Query::new(app.clone(), &metrics);
-    query.update_mempool()?;
 
-    let rpc = RPC::start(config.rpc_addr, query.clone(), &metrics);
-    while let None = signal.wait(Duration::from_secs(5)) {
-        if tip != app.daemon().getbestblockhash()? {
-            tip = app.index().update(app.write_store(), &signal)?;
-        }
+    let mut server = None;
+    loop {
+        app.update(&signal)?;
         query.update_mempool()?;
-        rpc.notify(); // update subscribed clients
+        server
+            .get_or_insert_with(|| RPC::start(config.rpc_addr, query.clone(), &metrics))
+            .notify(); // update subscribed clients
+        if signal.wait(Duration::from_secs(5)).is_some() {
+            break;
+        }
     }
-    rpc.exit();
+    server.map(|s| s.exit());
     Ok(())
 }