Re-order Zebra startup, so slow services are launched last (#3091)

* Start network before verifiers

This makes the Groth16 download task start as late as possible.

* Explain why the Groth16 download must happen first

* Speed up Zebra shutdown: skip waiting for the tokio runtime

zebra-consensus/src/chain.rs

@@ -197,7 +197,8 @@ where
     S: Service<zs::Request, Response = zs::Response, Error = BoxError> + Send + Clone + 'static,
     S::Future: Send + 'static,
 {
-    // pre-download Groth16 parameters async
+    // Pre-download Groth16 parameters in a separate thread.
+    // This thread must be launched first, so the download doesn't happen on the startup thread.
 
     let groth16_download_handle = spawn_blocking(|| {
         tracing::info!("checking if Zcash Sapling and Sprout parameters have been downloaded");

zebrad/src/commands/start.rs

@@ -56,6 +56,7 @@ use tower::{builder::ServiceBuilder, util::BoxService};
 
 use crate::{
     components::{
+        inbound::InboundSetupData,
         mempool::{self, Mempool},
         sync,
         tokio::{RuntimeRun, TokioComponent},
@@ -83,15 +84,6 @@ impl StartCmd {
             zebra_state::init(config.state.clone(), config.network.network);
         let state = ServiceBuilder::new().buffer(20).service(state_service);
 
-        info!("initializing verifiers");
-        let (chain_verifier, tx_verifier, mut groth16_download_handle) =
-            zebra_consensus::chain::init(
-                config.consensus.clone(),
-                config.network.network,
-                state.clone(),
-            )
-            .await;
-
         info!("initializing network");
         // The service that our node uses to respond to requests by peers. The
         // load_shed middleware ensures that we reduce the size of the peer set
@@ -100,24 +92,33 @@ impl StartCmd {
         let inbound = ServiceBuilder::new()
             .load_shed()
             .buffer(20)
-            .service(Inbound::new(
-                setup_rx,
-                state.clone(),
-                chain_verifier.clone(),
-            ));
+            .service(Inbound::new(setup_rx));
 
         let (peer_set, address_book) =
             zebra_network::init(config.network.clone(), inbound, latest_chain_tip.clone()).await;
 
+        info!("initializing verifiers");
+        let (chain_verifier, tx_verifier, mut groth16_download_handle) =
+            zebra_consensus::chain::init(
+                config.consensus.clone(),
+                config.network.network,
+                state.clone(),
+            )
+            .await;
+
         info!("initializing syncer");
-        let (syncer, sync_status) =
-            ChainSync::new(&config, peer_set.clone(), state.clone(), chain_verifier);
+        let (syncer, sync_status) = ChainSync::new(
+            &config,
+            peer_set.clone(),
+            state.clone(),
+            chain_verifier.clone(),
+        );
 
         info!("initializing mempool");
         let (mempool, mempool_transaction_receiver) = Mempool::new(
             &config.mempool,
             peer_set.clone(),
-            state,
+            state.clone(),
             tx_verifier,
             sync_status.clone(),
             latest_chain_tip,
@@ -126,8 +127,15 @@ impl StartCmd {
         let mempool = BoxService::new(mempool);
         let mempool = ServiceBuilder::new().buffer(20).service(mempool);
 
+        let setup_data = InboundSetupData {
+            address_book,
+            block_download_peer_set: peer_set.clone(),
+            block_verifier: chain_verifier,
+            mempool: mempool.clone(),
+            state,
+        };
         setup_tx
-            .send((peer_set.clone(), address_book, mempool.clone()))
+            .send(setup_data)
             .map_err(|_| eyre!("could not send setup data to inbound service"))?;
 
         let syncer_error_future = syncer.sync();

zebrad/src/components.rs

@@ -5,7 +5,7 @@
 //! component and dependency injection models are designed to work together, but
 //! don't fit the async context well.
 
-mod inbound;
+pub mod inbound;
 #[allow(missing_docs)]
 pub mod mempool;
 pub mod metrics;