[Performance] Investigate and decrease RAM usage - add pebble kvstore

Makefile

@@ -42,6 +42,10 @@ test_all:  ## runs the test suite
 test_badger: ## runs the badger KVStore submodule's test suite
 	go test -v -p 1 -count=1 ./kvstore/badger/... -mod=readonly -race
 
+.PHONY: test_pebble
+test_pebble: ## runs the pebble KVStore submodule's test suite
+	go test -v -p 1 -count=1 ./kvstore/pebble/... -mod=readonly -race
+
 
 #####################
 ###   go helpers  ###
@@ -93,6 +97,10 @@ benchmark_smst_ops:  ## runs the benchmarks test different operations on the SMS
 benchmark_proof_sizes:  ## runs the benchmarks test the proof sizes for different sized tries
 	go test -tags=benchmark -v ./benchmarks -run ProofSizes
 
+.PHONY: benchmark_pebble
+benchmark_pebble:  ## TODO: Add the pebble benchmarks
+	echo "TODO: Implement pebble benchmarks"
+
 ###########################
 ###   Release Helpers   ###
 ###########################
@@ -120,4 +128,4 @@ tag_minor_release: ## Tag a new minor release (e.g. v1.0.0 -> v1.1.0)
 	@echo "New minor release version tagged: $(NEW_TAG)"
 	@echo "Run the following commands to push the new tag:"
 	@echo "  git push origin $(NEW_TAG)"
-	@echo "And draft a new release at https://github.com/pokt-network/smt/releases/new"
+	@echo "And draft a new release at https://github.com/pokt-network/smt/releases/new"

go.work

@@ -1,8 +1,10 @@
 go 1.20
 
 use (
-    // Include the main SMT module
-    .
-    // Include the badger KVStore submodule
-    ./kvstore/badger
+	// Include the main SMT module
+	.
+	// Include the badger KVStore submodule
+	./kvstore/badger
+	// Include the pebble KVStore submodule
+	./kvstore/pebble
 )

go.work.sum

@@ -1,43 +1,111 @@
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kvstore/badger/errors.go

@@ -35,4 +35,7 @@ var (
 	// ErrBadgerGettingStoreLength is returned when the badger store fails to
 	// get the length of the database
 	ErrBadgerGettingStoreLength = errors.New("unable to get database length")
+	// ErrBadgerUnableToCheckExistence is returned when the badger store fails to
+	// check if a key exists
+	ErrBadgerUnableToCheckExistence = errors.New("unable to check key existence")
 )

kvstore/badger/interface.go

@@ -14,14 +14,7 @@ var _ kvstore.MapStore = (BadgerKVStore)(nil)
 // This is a superset of the MapStore interface that offers more
 // features and can be used as a standalone key-value store.
 type BadgerKVStore interface {
-	// --- Store methods ---
-
-	// Get returns the value for a given key
-	Get(key []byte) ([]byte, error)
-	// Set sets/updates the value for a given key
-	Set(key, value []byte) error
-	// Delete removes a key
-	Delete(key []byte) error
+	kvstore.MapStore
 
 	// --- Lifecycle methods ---
 
@@ -41,11 +34,4 @@ type BadgerKVStore interface {
 	GetAll(prefixKey []byte, descending bool) (keys, values [][]byte, err error)
 	// Exists returns true if the key exists
 	Exists(key []byte) (bool, error)
-	// Len returns the number of key-value pairs in the store
-	Len() int
-
-	// --- Data management ---
-
-	// ClearAll deletes all key-value pairs in the store
-	ClearAll() error
 }

kvstore/badger/kvstore.go

@@ -20,6 +20,8 @@ type badgerKVStore struct {
 
 // NewKVStore creates a new BadgerKVStore using badger as the underlying database
 // if no path for a persistence database is provided it will create one in-memory
+// TODO_CONSIDERATION: consider exposing the low-level options (`badgerv4.Options`) via a
+// config file to make it easier to test under different load conditions.
 func NewKVStore(path string) (BadgerKVStore, error) {
 	var db *badgerv4.DB
 	var err error
@@ -31,6 +33,7 @@ func NewKVStore(path string) (BadgerKVStore, error) {
 	if err != nil {
 		return nil, errors.Join(ErrBadgerOpeningStore, err)
 	}
+
 	return &badgerKVStore{db: db}, nil
 }
 
@@ -109,13 +112,26 @@ func (store *badgerKVStore) GetAll(prefix []byte, descending bool) (keys, values
 	return keys, values, nil
 }
 
-// Exists checks whether the key exists in the store
+// Exists checks whether the key exists in the store without retrieving the full value.
+// This avoids unnecessary memory allocations and copying that would occur with a full Get.
 func (store *badgerKVStore) Exists(key []byte) (bool, error) {
-	val, err := store.Get(key)
+	var exists bool
+	err := store.db.View(func(tx *badgerv4.Txn) error {
+		item, err := tx.Get(key)
+		if err != nil {
+			return err
+		}
+		// Check if the value is nil
+		err = item.Value(func(val []byte) error {
+			exists = len(val) > 0
+			return nil
+		})
+		return err
+	})
 	if err != nil {
-		return false, err
+		return false, errors.Join(ErrBadgerUnableToCheckExistence, err)
 	}
-	return val != nil, nil
+	return exists, nil
 }
 
 // ClearAll deletes all key-value pairs in the store
@@ -159,9 +175,9 @@ func (store *badgerKVStore) Stop() error {
 }
 
 // Len gives the number of keys in the store
-func (store *badgerKVStore) Len() int {
-	count := 0
-	if err := store.db.View(func(tx *badgerv4.Txn) error {
+func (store *badgerKVStore) Len() (int, error) {
+	var count int
+	err := store.db.View(func(tx *badgerv4.Txn) error {
 		opt := badgerv4.DefaultIteratorOptions
 		opt.Prefix = []byte{}
 		opt.Reverse = false
@@ -171,14 +187,22 @@ func (store *badgerKVStore) Len() int {
 			count++
 		}
 		return nil
-	}); err != nil {
-		panic(errors.Join(ErrBadgerGettingStoreLength, err))
+	})
+	if err != nil {
+		return 0, errors.Join(ErrBadgerGettingStoreLength, err)
 	}
-	return count
+	return count, nil
 }
 
-// PrefixEndBytes returns the end byteslice for a noninclusive range
-// that would include all byte slices for which the input is the prefix
+// prefixEndBytes returns the end byteslice for a noninclusive range
+// that would include all byte slices for which the input is the prefix.
+// It's used in reverse iteration to set the upper bound of the key range.
+//
+// Example:
+// If prefix is []byte("user:1"), prefixEndBytes returns []byte("user:2").
+// This ensures that in reverse iteration:
+// - Keys like "user:1", "user:1:profile", "user:10" are included.
+// - But "user:2", "user:2:profile" are not included.
 func prefixEndBytes(prefix []byte) []byte {
 	if len(prefix) == 0 {
 		return nil
@@ -194,7 +218,16 @@ func prefixEndBytes(prefix []byte) []byte {
 
 // badgerOptions returns the badger options for the store being created
 func badgerOptions(path string) badgerv4.Options {
+	// DEV_NOTE: Parameters should be adjusted carefully, depending on the type of load. We need to experiment more to find the best
+	// values, and even then they might need further adjustments as the type of load/environment (e.g. memory dedicated
+	// to the process) changes.
+	//
+	// Good links to read about options:
+	// - https://github.com/dgraph-io/badger/issues/1304#issuecomment-630078745
+	// - https://github.com/dgraph-io/badger/blob/master/options.go#L37
+	// - https://github.com/open-policy-agent/opa/issues/4014#issuecomment-1003700744
 	opts := badgerv4.DefaultOptions(path)
 	opts.Logger = nil // disable badger's logger since it's very noisy
+
 	return opts
 }

kvstore/badger/kvstore_test.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/stretchr/testify/require"
 
+	badgerv4 "github.com/dgraph-io/badger/v4"
 	"github.com/pokt-network/smt/kvstore/badger"
 )
 
@@ -280,7 +281,7 @@ func TestBadger_KVStore_Exists(t *testing.T) {
 
 	// Key does not exist
 	exists, err = store.Exists([]byte("oof"))
-	require.ErrorIs(t, err, badger.ErrBadgerUnableToGetValue)
+	require.ErrorIs(t, err, badgerv4.ErrKeyNotFound)
 	require.False(t, exists)
 
 	err = store.Stop()
@@ -389,7 +390,9 @@ func TestBadger_KVStore_Len(t *testing.T) {
 
 	for _, tc := range tests {
 		require.NoError(t, store.Set(tc.key, tc.value))
-		require.Equal(t, tc.size, store.Len())
+		len, err := store.Len()
+		require.NoError(t, err)
+		require.Equal(t, tc.size, len)
 	}
 }
 

kvstore/interfaces.go

@@ -13,7 +13,7 @@ type MapStore interface {
 	// Delete removes a key
 	Delete(key []byte) error
 	// Len returns the number of key-value pairs in the store
-	Len() int
+	Len() (int, error)
 
 	// --- Debug ---
 

kvstore/pebble/errors.go

@@ -0,0 +1,36 @@
+package pebble
+
+import "errors"
+
+// Error definitions
+var (
+	// ErrPebbleOpeningStore is returned when there's an error opening the Pebble database.
+	ErrPebbleOpeningStore = errors.New("error opening the store")
+
+	// ErrPebbleUnableToSetValue is returned when a value cannot be set in the store.
+	ErrPebbleUnableToSetValue = errors.New("unable to set value")
+
+	// ErrPebbleUnableToGetValue is returned when a value cannot be retrieved from the store.
+	ErrPebbleUnableToGetValue = errors.New("unable to get value")
+
+	// ErrPebbleUnableToDeleteValue is returned when a value cannot be deleted from the store.
+	ErrPebbleUnableToDeleteValue = errors.New("unable to delete value")
+
+	// ErrPebbleIteratingStore is returned when there's an error iterating over the database.
+	ErrPebbleIteratingStore = errors.New("unable to iterate over database")
+
+	// ErrPebbleClearingStore is returned when there's an error clearing all data from the store.
+	ErrPebbleClearingStore = errors.New("unable to clear store")
+
+	// ErrPebbleUnableToBackup is returned when there's an error backing up the database.
+	ErrPebbleUnableToBackup = errors.New("unable to backup database")
+
+	// ErrPebbleUnableToRestore is returned when there's an error restoring the database from a backup.
+	ErrPebbleUnableToRestore = errors.New("unable to restore database")
+
+	// ErrPebbleClosingStore is returned when there's an error closing the database connection.
+	ErrPebbleClosingStore = errors.New("unable to close database")
+
+	// ErrPebbleGettingStoreLength is returned when there's an error getting the number of key-value pairs in the database.
+	ErrPebbleGettingStoreLength = errors.New("unable to get database length")
+)