refactor(leader_schedule): SlotLeaderProvider from PointerClosure to direct SlotLeaders struct

src/cmd/cmd.zig

@@ -767,7 +767,7 @@ fn validator() !void {
     }
     // This provider will fail at epoch boundary unless another thread updated the leader schedule cache
     // i.e. called leader_schedule_cache.getSlotLeaderMaybeCompute(slot, bank_fields);
-    const leader_provider = leader_schedule_cache.slotLeaderProvider();
+    const leader_provider = leader_schedule_cache.slotLeaders();
 
     // blockstore
     var blockstore_db = try sig.ledger.BlockstoreDB.open(
@@ -885,7 +885,7 @@ fn shredCollector() !void {
     }
     // This provider will fail at epoch boundary unless another thread updated the leader schedule cache
     // i.e. called leader_schedule_cache.getSlotLeaderMaybeCompute(slot, bank_fields);
-    const leader_provider = leader_schedule_cache.slotLeaderProvider();
+    const leader_provider = leader_schedule_cache.slotLeaders();
 
     // blockstore
     var blockstore_db = try sig.ledger.BlockstoreDB.open(

src/core/leader_schedule.zig

@@ -14,18 +14,40 @@ const RwMux = sig.sync.RwMux;
 pub const NUM_CONSECUTIVE_LEADER_SLOTS: u64 = 4;
 pub const MAX_CACHED_LEADER_SCHEDULES: usize = 10;
 
-pub const SlotLeaderProvider = sig.utils.closure.PointerClosure(Slot, ?Pubkey);
+/// interface to express a dependency on slot leaders
+pub const SlotLeaders = struct {
+    state: *anyopaque,
+    getFn: *const fn (*anyopaque, Slot) ?Pubkey,
+
+    pub fn init(
+        state: anytype,
+        getSlotLeader: fn (@TypeOf(state), Slot) ?Pubkey,
+    ) SlotLeaders {
+        return .{
+            .state = state,
+            .getFn = struct {
+                fn genericFn(generic_state: *anyopaque, slot: Slot) ?Pubkey {
+                    return getSlotLeader(@alignCast(@ptrCast(generic_state)), slot);
+                }
+            }.genericFn,
+        };
+    }
+
+    pub fn get(self: SlotLeaders, slot: Slot) ?Pubkey {
+        return self.getFn(self.state, slot);
+    }
+};
 
 /// LeaderScheduleCache is a cache of leader schedules for each epoch.
 /// Leader schedules are expensive to compute, so this cache is used to avoid
 /// recomputing leader schedules for the same epoch.
 /// LeaderScheduleCache also keeps a copy of the epoch_schedule so that it can
 /// compute epoch and slot index from a slot.
 /// NOTE: This struct is not really a 'cache', we should consider renaming it
-/// to a SlotLeaderProvider and maybe even moving it outside of the core module.
+/// to a SlotLeaders and maybe even moving it outside of the core module.
 /// This more accurately describes the purpose of this struct as caching is a means
 /// to an end, not the end itself. It may then follow that we could remove the
-/// above pointer closure in favor of passing the SlotLeaderProvider directly.
+/// above pointer closure in favor of passing the SlotLeaders directly.
 pub const LeaderScheduleCache = struct {
     epoch_schedule: EpochSchedule,
     leader_schedules: RwMux(std.AutoArrayHashMap(Epoch, LeaderSchedule)),
@@ -41,8 +63,8 @@ pub const LeaderScheduleCache = struct {
         };
     }
 
-    pub fn slotLeaderProvider(self: *Self) SlotLeaderProvider {
-        return SlotLeaderProvider.init(self, LeaderScheduleCache.slotLeader);
+    pub fn slotLeaders(self: *Self) SlotLeaders {
+        return SlotLeaders.init(self, LeaderScheduleCache.slotLeader);
     }
 
     pub fn put(self: *Self, epoch: Epoch, leader_schedule: LeaderSchedule) !void {

src/ledger/shred_inserter/shred_inserter.zig

@@ -23,7 +23,7 @@ const CodeShred = ledger.shred.CodeShred;
 const DataShred = ledger.shred.DataShred;
 const ReedSolomonCache = lib.recovery.ReedSolomonCache;
 const ShredId = ledger.shred.ShredId;
-const SlotLeaderProvider = sig.core.leader_schedule.SlotLeaderProvider;
+const SlotLeaders = sig.core.leader_schedule.SlotLeaders;
 const SortedSet = sig.utils.collections.SortedSet;
 const SortedMap = sig.utils.collections.SortedMap;
 const Timer = sig.time.Timer;
@@ -145,7 +145,7 @@ pub const ShredInserter = struct {
         self: *Self,
         shreds: []const Shred,
         is_repaired: []const bool,
-        leader_schedule: ?SlotLeaderProvider,
+        maybe_slot_leaders: ?SlotLeaders,
         is_trusted: bool,
         retransmit_sender: ?PointerClosure([]const []const u8, void),
     ) !InsertShredsResult {
@@ -195,7 +195,7 @@ pub const ShredInserter = struct {
                         merkle_root_validator,
                         write_batch,
                         is_trusted,
-                        leader_schedule,
+                        maybe_slot_leaders,
                         shred_source,
                     )) |completed_data_sets| {
                         if (is_repair) {
@@ -239,7 +239,7 @@ pub const ShredInserter = struct {
         var shred_recovery_timer = try Timer.start();
         var valid_recovered_shreds = ArrayList([]const u8).init(allocator);
         defer valid_recovered_shreds.deinit();
-        if (leader_schedule) |slot_leader_provider| {
+        if (maybe_slot_leaders) |slot_leaders| {
             var reed_solomon_cache = try ReedSolomonCache.init(allocator);
             defer reed_solomon_cache.deinit();
             const recovered_shreds = try self.tryShredRecovery(
@@ -259,7 +259,7 @@ pub const ShredInserter = struct {
                 if (shred == .data) {
                     self.metrics.num_recovered.inc();
                 }
-                const leader = slot_leader_provider.call(shred.commonHeader().slot);
+                const leader = slot_leaders.get(shred.commonHeader().slot);
                 if (leader == null) {
                     continue;
                 }
@@ -280,7 +280,7 @@ pub const ShredInserter = struct {
                     merkle_root_validator,
                     write_batch,
                     is_trusted,
-                    leader_schedule,
+                    maybe_slot_leaders,
                     .recovered,
                 )) |completed_data_sets| {
                     defer completed_data_sets.deinit();
@@ -590,7 +590,7 @@ pub const ShredInserter = struct {
         merkle_root_validator: MerkleRootValidator,
         write_batch: *WriteBatch,
         is_trusted: bool,
-        leader_schedule: ?SlotLeaderProvider,
+        leader_schedule: ?SlotLeaders,
         shred_source: ShredSource,
     ) !ArrayList(CompletedDataSetInfo) {
         const slot = shred.common.slot;
@@ -708,7 +708,7 @@ pub const ShredInserter = struct {
         slot_meta: *const SlotMeta,
         shred_store: ShredWorkingStore,
         max_root: Slot,
-        leader_schedule: ?SlotLeaderProvider,
+        leader_schedule: ?SlotLeaders,
         shred_source: ShredSource,
         duplicate_shreds: *ArrayList(PossibleDuplicateShred),
     ) !bool {
@@ -975,8 +975,8 @@ fn verifyShredSlots(slot: Slot, parent: Slot, root: Slot) bool {
     return root <= parent and parent < slot;
 }
 
-fn slotLeader(provider: ?SlotLeaderProvider, slot: Slot) ?Pubkey {
-    return if (provider) |p| if (p.call(slot)) |l| l else null else null;
+fn slotLeader(provider: ?SlotLeaders, slot: Slot) ?Pubkey {
+    return if (provider) |p| if (p.get(slot)) |l| l else null else null;
 }
 
 /// update_slot_meta
@@ -1486,7 +1486,7 @@ test "recovery" {
     const data_shreds = shreds[0..34];
     const code_shreds = shreds[34..68];
 
-    var leader_schedule = OneSlotLeaderProvider{
+    var leader_schedule = OneSlotLeaders{
         .leader = try Pubkey.fromString("2iWGQbhdWWAA15KTBJuqvAxCdKmEvY26BoFRBU4419Sn"),
     };
 
@@ -1512,15 +1512,15 @@ test "recovery" {
     // TODO: verify index integrity
 }
 
-const OneSlotLeaderProvider = struct {
+const OneSlotLeaders = struct {
     leader: Pubkey,
 
-    fn getLeader(self: *OneSlotLeaderProvider, _: Slot) ?Pubkey {
+    fn getLeader(self: *OneSlotLeaders, _: Slot) ?Pubkey {
         return self.leader;
     }
 
-    fn provider(self: *OneSlotLeaderProvider) SlotLeaderProvider {
-        return SlotLeaderProvider.init(self, OneSlotLeaderProvider.getLeader);
+    fn provider(self: *OneSlotLeaders) SlotLeaders {
+        return SlotLeaders.init(self, OneSlotLeaders.getLeader);
     }
 };
 

src/shred_network/service.zig

@@ -19,7 +19,7 @@ const RwMux = sig.sync.RwMux;
 const Registry = sig.prometheus.Registry;
 const ServiceManager = sig.utils.service_manager.ServiceManager;
 const Slot = sig.core.Slot;
-const SlotLeaderProvider = sig.core.leader_schedule.SlotLeaderProvider;
+const SlotLeaders = sig.core.leader_schedule.SlotLeaders;
 const LeaderScheduleCache = sig.core.leader_schedule.LeaderScheduleCache;
 
 const BasicShredTracker = shred_network.shred_tracker.BasicShredTracker;
@@ -52,7 +52,7 @@ pub const ShredCollectorDependencies = struct {
     /// Shared state that is read from gossip
     my_shred_version: *const Atomic(u16),
     my_contact_info: ThreadSafeContactInfo,
-    leader_schedule: SlotLeaderProvider,
+    leader_schedule: SlotLeaders,
     shred_inserter: sig.ledger.ShredInserter,
     n_retransmit_threads: ?usize,
     overwrite_turbine_stake_for_testing: bool,

src/shred_network/shred_processor.zig

@@ -33,7 +33,7 @@ pub fn runShredProcessor(
     verified_shred_receiver: *Channel(Packet),
     tracker: *BasicShredTracker,
     shred_inserter_: ShredInserter,
-    leader_schedule: sig.core.leader_schedule.SlotLeaderProvider,
+    leader_schedule: sig.core.leader_schedule.SlotLeaders,
 ) !void {
     const logger = logger_.withScope(LOG_SCOPE);
     var shred_inserter = shred_inserter_;

src/shred_network/shred_verifier.zig

@@ -10,7 +10,7 @@ const Counter = sig.prometheus.Counter;
 const Histogram = sig.prometheus.Histogram;
 const Packet = sig.net.Packet;
 const Registry = sig.prometheus.Registry;
-const SlotLeaderProvider = sig.core.leader_schedule.SlotLeaderProvider;
+const SlotLeaders = sig.core.leader_schedule.SlotLeaders;
 const VariantCounter = sig.prometheus.VariantCounter;
 
 const VerifiedMerkleRoots = sig.common.lru.LruCache(.non_locking, sig.core.Hash, void);
@@ -25,7 +25,7 @@ pub fn runShredVerifier(
     verified_shred_sender: *Channel(Packet),
     /// me --> retransmit service
     maybe_retransmit_shred_sender: ?*Channel(Packet),
-    leader_schedule: SlotLeaderProvider,
+    leader_schedule: SlotLeaders,
 ) !void {
     const metrics = try registry.initStruct(Metrics);
     var verified_merkle_roots = try VerifiedMerkleRoots.init(std.heap.c_allocator, 1024);
@@ -53,7 +53,7 @@ pub fn runShredVerifier(
 /// Analogous to [verify_shred_cpu](https://github.com/anza-xyz/agave/blob/83e7d84bcc4cf438905d07279bc07e012a49afd9/ledger/src/sigverify_shreds.rs#L35)
 fn verifyShred(
     packet: *const Packet,
-    leader_schedule: SlotLeaderProvider,
+    leader_schedule: SlotLeaders,
     verified_merkle_roots: *VerifiedMerkleRoots,
     metrics: Metrics,
 ) ShredVerificationFailure!void {
@@ -66,7 +66,7 @@ fn verifyShred(
         return;
     }
     metrics.cache_miss_count.inc();
-    const leader = leader_schedule.call(slot) orelse return error.leader_unknown;
+    const leader = leader_schedule.get(slot) orelse return error.leader_unknown;
     const valid = signature.verify(leader, &signed_data.data) catch
         return error.failed_verification;
     if (!valid) return error.failed_verification;