Modularize beacon node backend (#4718)

#4669


  Modularize the beacon node backend to make it easier to add new database implementations

beacon_node/src/cli.rs

@@ -1591,5 +1591,14 @@ pub fn cli_app() -> Command {
                 .action(ArgAction::Set)
                 .display_order(0)
         )
+        .arg(
+            Arg::new("beacon-node-backend")
+                .long("beacon-node-backend")
+                .value_name("DATABASE")
+                .value_parser(store::config::DatabaseBackend::VARIANTS.to_vec())
+                .help("Set the database backend to be used by the beacon node.")
+                .action(ArgAction::Set)
+                .display_order(0)
+        )
         .group(ArgGroup::new("enable_http").args(["http", "gui", "staking"]).multiple(true))
 }

beacon_node/src/config.rs

@@ -432,6 +432,10 @@ pub fn get_config<E: EthSpec>(
         warn!(log, "The slots-per-restore-point flag is deprecated");
     }
 
+    if let Some(backend) = clap_utils::parse_optional(cli_args, "beacon-node-backend")? {
+        client_config.store.backend = backend;
+    }
+
     if let Some(hierarchy_config) = clap_utils::parse_optional(cli_args, "hierarchy-exponents")? {
         client_config.store.hierarchy_config = hierarchy_config;
     }

beacon_node/src/lib.rs

@@ -2,7 +2,6 @@ mod cli;
 mod config;
 
 pub use beacon_chain;
-use beacon_chain::store::LevelDB;
 use beacon_chain::{
     builder::Witness, eth1_chain::CachingEth1Backend, slot_clock::SystemTimeSlotClock,
 };
@@ -16,11 +15,19 @@ use slasher::{DatabaseBackendOverride, Slasher};
 use slog::{info, warn};
 use std::ops::{Deref, DerefMut};
 use std::sync::Arc;
+use store::database::interface::BeaconNodeBackend;
 use types::{ChainSpec, Epoch, EthSpec, ForkName};
 
 /// A type-alias to the tighten the definition of a production-intended `Client`.
-pub type ProductionClient<E> =
-    Client<Witness<SystemTimeSlotClock, CachingEth1Backend<E>, E, LevelDB<E>, LevelDB<E>>>;
+pub type ProductionClient<E> = Client<
+    Witness<
+        SystemTimeSlotClock,
+        CachingEth1Backend<E>,
+        E,
+        BeaconNodeBackend<E>,
+        BeaconNodeBackend<E>,
+    >,
+>;
 
 /// The beacon node `Client` that will be used in production.
 ///