Add SnapshotUsage to SnapshotConfig (#27508)

core/src/accounts_hash_verifier.rs

@@ -276,7 +276,9 @@ impl AccountsHashVerifier {
     ) {
         if accounts_package.snapshot_type.is_none()
             || pending_snapshot_package.is_none()
-            || snapshot_config.is_none()
+            || !snapshot_config
+                .map(|snapshot_config| snapshot_config.should_generate_snapshots())
+                .unwrap_or(false)
         {
             return;
         };

ledger-tool/src/main.rs

@@ -946,12 +946,10 @@ fn load_bank_forks(
         }
 
         Some(SnapshotConfig {
-            full_snapshot_archive_interval_slots: Slot::MAX,
-            incremental_snapshot_archive_interval_slots: Slot::MAX,
             full_snapshot_archives_dir,
             incremental_snapshot_archives_dir,
             bank_snapshots_dir,
-            ..SnapshotConfig::default()
+            ..SnapshotConfig::new_load_only()
         })
     };
 

local-cluster/src/local_cluster.rs

@@ -745,7 +745,7 @@ impl LocalCluster {
             incremental_snapshot_archive_interval_slots: Slot::MAX,
             full_snapshot_archives_dir: DUMMY_SNAPSHOT_CONFIG_PATH_MARKER.into(),
             bank_snapshots_dir: DUMMY_SNAPSHOT_CONFIG_PATH_MARKER.into(),
-            ..SnapshotConfig::default()
+            ..SnapshotConfig::new_load_only()
         }
     }
 }

local-cluster/tests/common.rs

@@ -457,6 +457,7 @@ impl SnapshotValidatorConfig {
     ) -> SnapshotValidatorConfig {
         assert!(accounts_hash_interval_slots > 0);
         assert!(full_snapshot_archive_interval_slots > 0);
+        assert!(full_snapshot_archive_interval_slots != Slot::MAX);
         assert!(full_snapshot_archive_interval_slots % accounts_hash_interval_slots == 0);
         if incremental_snapshot_archive_interval_slots != Slot::MAX {
             assert!(incremental_snapshot_archive_interval_slots > 0);

runtime/src/snapshot_config.rs

@@ -7,6 +7,9 @@ use {
 /// Snapshot configuration and runtime information
 #[derive(Clone, Debug)]
 pub struct SnapshotConfig {
+    /// Specifies the ways thats snapshots are allowed to be used
+    pub usage: SnapshotUsage,
+
     /// Generate a new full snapshot archive every this many slots
     pub full_snapshot_archive_interval_slots: Slot,
 
@@ -45,6 +48,7 @@ pub struct SnapshotConfig {
 impl Default for SnapshotConfig {
     fn default() -> Self {
         Self {
+            usage: SnapshotUsage::LoadAndGenerate,
             full_snapshot_archive_interval_slots:
                 snapshot_utils::DEFAULT_FULL_SNAPSHOT_ARCHIVE_INTERVAL_SLOTS,
             incremental_snapshot_archive_interval_slots:
@@ -63,3 +67,30 @@ impl Default for SnapshotConfig {
         }
     }
 }
+
+impl SnapshotConfig {
+    /// A new snapshot config used for only loading at startup
+    #[must_use]
+    pub fn new_load_only() -> Self {
+        Self {
+            usage: SnapshotUsage::LoadOnly,
+            ..Self::default()
+        }
+    }
+
+    /// Should snapshots be generated?
+    #[must_use]
+    pub fn should_generate_snapshots(&self) -> bool {
+        self.usage == SnapshotUsage::LoadAndGenerate
+    }
+}
+
+/// Specify the ways that snapshots are allowed to be used
+#[derive(Debug, Clone, Eq, PartialEq)]
+pub enum SnapshotUsage {
+    /// Snapshots are only used at startup, to load the accounts and bank
+    LoadOnly,
+    /// Snapshots are used everywhere; both at startup (i.e. load) and steady-state (i.e.
+    /// generate).  This enables taking snapshots.
+    LoadAndGenerate,
+}

validator/src/main.rs

@@ -50,7 +50,7 @@ use {
         },
         hardened_unpack::MAX_GENESIS_ARCHIVE_UNPACKED_SIZE,
         runtime_config::RuntimeConfig,
-        snapshot_config::SnapshotConfig,
+        snapshot_config::{SnapshotConfig, SnapshotUsage},
         snapshot_utils::{
             self, ArchiveFormat, SnapshotVersion, DEFAULT_ARCHIVE_COMPRESSION,
             DEFAULT_FULL_SNAPSHOT_ARCHIVE_INTERVAL_SLOTS,
@@ -2929,6 +2929,11 @@ pub fn main() {
         };
 
     validator_config.snapshot_config = Some(SnapshotConfig {
+        usage: if full_snapshot_archive_interval_slots == Slot::MAX {
+            SnapshotUsage::LoadOnly
+        } else {
+            SnapshotUsage::LoadAndGenerate
+        },
         full_snapshot_archive_interval_slots,
         incremental_snapshot_archive_interval_slots,
         bank_snapshots_dir,