Configurable epochs-per-state-diff

beacon_node/src/cli.rs

@@ -566,6 +566,16 @@ pub fn cli_app<'a, 'b>() -> App<'a, 'b> {
                 .default_value("4")
                 .takes_value(true)
         )
+        .arg(
+            Arg::with_name("epochs-per-state-diff")
+                .long("epochs-per-state-diff")
+                .value_name("EPOCHS")
+                .help("Number of epochs between state diffs stored in the database. Lower values \
+                       result in more writes and more data stored, while higher values result in \
+                       more block replaying and longer load times in case of cache miss.")
+                .default_value("4")
+                .takes_value(true)
+        )
         /*
          * Misc.
          */

beacon_node/src/config.rs

@@ -403,6 +403,12 @@ pub fn get_config<E: EthSpec>(
         client_config.store_migrator.epochs_per_run = epochs_per_migration;
     }
 
+    if let Some(epochs_per_state_diff) =
+        clap_utils::parse_optional(cli_args, "epochs-per-state-diff")?
+    {
+        client_config.store.epochs_per_state_diff = epochs_per_state_diff;
+    }
+
     /*
      * Zero-ports
      *

lighthouse/tests/beacon_node.rs

@@ -1371,6 +1371,24 @@ fn db_migration_period_override() {
         .run_with_zero_port()
         .with_config(|config| assert_eq!(config.store_migrator.epochs_per_run, 128));
 }
+#[test]
+fn epochs_per_state_diff_default() {
+    CommandLineTest::new()
+        .run_with_zero_port()
+        .with_config(|config| {
+            assert_eq!(
+                config.store.epochs_per_state_diff,
+                beacon_node::beacon_chain::store::config::DEFAULT_EPOCHS_PER_STATE_DIFF
+            )
+        });
+}
+#[test]
+fn epochs_per_state_diff_override() {
+    CommandLineTest::new()
+        .flag("epochs-per-state-diff", Some("1"))
+        .run_with_zero_port()
+        .with_config(|config| assert_eq!(config.store.epochs_per_state_diff, 1));
+}
 
 // Tests for Slasher flags.
 #[test]