soroban-rpc: Allow Budget Instruction Leeway to be Configured by Clients

cmd/soroban-rpc/internal/methods/simulate_transaction.go

@@ -15,7 +15,8 @@ import (
 )
 
 type SimulateTransactionRequest struct {
-	Transaction string `json:"transaction"`
+	Transaction    string                    `json:"transaction"`
+	ResourceConfig *preflight.ResourceConfig `json:"resourceConfig,omitempty"`
 }
 
 type SimulateTransactionCost struct {
@@ -46,7 +47,7 @@ type SimulateTransactionResponse struct {
 }
 
 type PreflightGetter interface {
-	GetPreflight(ctx context.Context, readTx db.LedgerEntryReadTx, bucketListSize uint64, sourceAccount xdr.AccountId, opBody xdr.OperationBody, footprint xdr.LedgerFootprint) (preflight.Preflight, error)
+	GetPreflight(ctx context.Context, readTx db.LedgerEntryReadTx, bucketListSize uint64, sourceAccount xdr.AccountId, opBody xdr.OperationBody, footprint xdr.LedgerFootprint, resourceConfig *preflight.ResourceConfig) (preflight.Preflight, error)
 }
 
 // NewSimulateTransactionHandler returns a json rpc handler to run preflight simulations
@@ -113,7 +114,7 @@ func NewSimulateTransactionHandler(logger *log.Entry, ledgerEntryReader db.Ledge
 			}
 		}
 
-		result, err := getter.GetPreflight(ctx, readTx, bucketListSize, sourceAccount, op.Body, footprint)
+		result, err := getter.GetPreflight(ctx, readTx, bucketListSize, sourceAccount, op.Body, footprint, request.ResourceConfig)
 		if err != nil {
 			return SimulateTransactionResponse{
 				Error:        err.Error(),

cmd/soroban-rpc/internal/preflight/pool.go

@@ -139,7 +139,7 @@ func (m *metricsLedgerEntryWrapper) GetLedgerEntries(keys ...xdr.LedgerKey) ([]d
 	return entries, err
 }
 
-func (pwp *PreflightWorkerPool) GetPreflight(ctx context.Context, readTx db.LedgerEntryReadTx, bucketListSize uint64, sourceAccount xdr.AccountId, opBody xdr.OperationBody, footprint xdr.LedgerFootprint) (Preflight, error) {
+func (pwp *PreflightWorkerPool) GetPreflight(ctx context.Context, readTx db.LedgerEntryReadTx, bucketListSize uint64, sourceAccount xdr.AccountId, opBody xdr.OperationBody, footprint xdr.LedgerFootprint, resourceConfig *ResourceConfig) (Preflight, error) {
 	if pwp.isClosed.Load() {
 		return Preflight{}, errors.New("preflight worker pool is closed")
 	}
@@ -154,6 +154,7 @@ func (pwp *PreflightWorkerPool) GetPreflight(ctx context.Context, readTx db.Ledg
 		LedgerEntryReadTx: &wrappedTx,
 		BucketListSize:    bucketListSize,
 		Footprint:         footprint,
+		ResourceConfig:    resourceConfig,
 		EnableDebug:       pwp.enableDebug,
 	}
 	resultC := make(chan workerResult)

cmd/soroban-rpc/internal/preflight/preflight.go

@@ -35,6 +35,10 @@ type snapshotSourceHandle struct {
 	logger *log.Entry
 }
 
+const (
+	defaultInstructionLeeway uint64 = 1000000
+)
+
 // SnapshotSourceGet takes a LedgerKey XDR in base64 string and returns its matching LedgerEntry XDR in base64 string
 // It's used by the Rust preflight code to obtain ledger entries.
 //
@@ -71,6 +75,10 @@ func FreeGoXDR(xdr C.xdr_t) {
 	C.free(unsafe.Pointer(xdr.xdr))
 }
 
+type ResourceConfig struct {
+	InstructionLeeway uint64 `json:"instructionLeeway"`
+}
+
 type PreflightParameters struct {
 	Logger            *log.Entry
 	SourceAccount     xdr.AccountId
@@ -79,6 +87,7 @@ type PreflightParameters struct {
 	NetworkPassphrase string
 	LedgerEntryReadTx db.LedgerEntryReadTx
 	BucketListSize    uint64
+	ResourceConfig    *ResourceConfig
 	EnableDebug       bool
 }
 
@@ -216,12 +225,20 @@ func getInvokeHostFunctionPreflight(params PreflightParameters) (Preflight, erro
 
 	handle := cgo.NewHandle(snapshotSourceHandle{params.LedgerEntryReadTx, params.Logger})
 	defer handle.Delete()
+	instructionLeeway := defaultInstructionLeeway
+	if params.ResourceConfig != nil {
+		instructionLeeway = params.ResourceConfig.InstructionLeeway
+	}
+	resourceConfig := C.resource_config_t{
+		instruction_leeway: C.uint64_t(instructionLeeway),
+	}
 	res := C.preflight_invoke_hf_op(
 		C.uintptr_t(handle),
 		C.uint64_t(params.BucketListSize),
 		invokeHostFunctionCXDR,
 		sourceAccountCXDR,
 		li,
+		resourceConfig,
 		C.bool(params.EnableDebug),
 	)
 	FreeGoXDR(invokeHostFunctionCXDR)

cmd/soroban-rpc/lib/preflight.h

@@ -25,6 +25,10 @@ typedef struct xdr_vector_t {
     size_t len;
 } xdr_vector_t;
 
+typedef struct resource_config_t {
+    uint64_t instruction_leeway; // Allow this many extra instructions when budgeting
+} resource_config_t;
+
 typedef struct preflight_result_t {
     char          *error; // Error string in case of error, otherwise null
     xdr_vector_t  auth; // array of SorobanAuthorizationEntries
@@ -43,6 +47,7 @@ preflight_result_t *preflight_invoke_hf_op(uintptr_t handle, // Go Handle to for
                                            const xdr_t invoke_hf_op, // InvokeHostFunctionOp XDR
                                            const xdr_t source_account, // AccountId XDR
                                            const ledger_info_t ledger_info,
+                                           const resource_config_t resource_config,
                                            bool enable_debug);
 
 preflight_result_t *preflight_footprint_ttl_op(uintptr_t   handle, // Go Handle to forward to SnapshotSourceGet

cmd/soroban-rpc/lib/preflight/src/fees.rs

@@ -23,21 +23,28 @@ use state_ttl::{get_restored_ledger_sequence, TTLLedgerEntry};
 use std::cmp::max;
 use std::convert::{TryFrom, TryInto};
 
+use crate::CResourceConfig;
+
 #[allow(clippy::too_many_arguments)]
 pub(crate) fn compute_host_function_transaction_data_and_min_fee(
     op: &InvokeHostFunctionOp,
     pre_storage: &LedgerStorage,
     post_storage: &Storage,
     budget: &Budget,
+    resource_config: CResourceConfig,
     events: &[DiagnosticEvent],
     invocation_result: &ScVal,
     bucket_list_size: u64,
     current_ledger_seq: u32,
 ) -> Result<(SorobanTransactionData, i64)> {
     let ledger_changes = get_ledger_changes(budget, post_storage, pre_storage, TtlEntryMap::new())?;
-    let soroban_resources =
-        calculate_host_function_soroban_resources(&ledger_changes, &post_storage.footprint, budget)
-            .context("cannot compute host function resources")?;
+    let soroban_resources = calculate_host_function_soroban_resources(
+        &ledger_changes,
+        &post_storage.footprint,
+        budget,
+        resource_config,
+    )
+    .context("cannot compute host function resources")?;
 
     let contract_events_size =
         calculate_contract_events_size_bytes(events).context("cannot calculate events size")?;
@@ -128,6 +135,7 @@ fn calculate_host_function_soroban_resources(
     ledger_changes: &[LedgerEntryChange],
     footprint: &Footprint,
     budget: &Budget,
+    resource_config: CResourceConfig,
 ) -> Result<SorobanResources> {
     let ledger_footprint = storage_footprint_to_ledger_footprint(footprint)
         .context("cannot convert storage footprint to ledger footprint")?;
@@ -143,7 +151,7 @@ fn calculate_host_function_soroban_resources(
         .get_cpu_insns_consumed()
         .context("cannot get instructions consumed")?;
     let instructions = max(
-        budget_instructions + 1000000,
+        budget_instructions + resource_config.instruction_leeway,
         budget_instructions * 120 / 100,
     );
     Ok(SorobanResources {

cmd/soroban-rpc/lib/preflight/src/lib.rs

@@ -81,6 +81,12 @@ fn get_default_c_xdr_vector() -> CXDRVector {
     }
 }
 
+#[repr(C)]
+#[derive(Copy, Clone)]
+pub struct CResourceConfig {
+    pub instruction_leeway: u64,
+}
+
 #[repr(C)]
 #[derive(Copy, Clone)]
 pub struct CPreflightResult {
@@ -133,6 +139,7 @@ pub extern "C" fn preflight_invoke_hf_op(
     invoke_hf_op: CXDR,      // InvokeHostFunctionOp XDR in base64
     source_account: CXDR,    // AccountId XDR in base64
     ledger_info: CLedgerInfo,
+    resource_config: CResourceConfig,
     enable_debug: bool,
 ) -> *mut CPreflightResult {
     catch_preflight_panic(Box::new(move || {
@@ -142,6 +149,7 @@ pub extern "C" fn preflight_invoke_hf_op(
             invoke_hf_op,
             source_account,
             ledger_info,
+            resource_config,
             enable_debug,
         )
     }))
@@ -153,6 +161,7 @@ fn preflight_invoke_hf_op_or_maybe_panic(
     invoke_hf_op: CXDR,    // InvokeHostFunctionOp XDR in base64
     source_account: CXDR,  // AccountId XDR in base64
     ledger_info: CLedgerInfo,
+    resource_config: CResourceConfig,
     enable_debug: bool,
 ) -> Result<CPreflightResult> {
     let invoke_hf_op =
@@ -166,6 +175,7 @@ fn preflight_invoke_hf_op_or_maybe_panic(
         invoke_hf_op,
         source_account,
         LedgerInfo::from(ledger_info),
+        resource_config,
         enable_debug,
     )?;
     Ok(result.into())

cmd/soroban-rpc/lib/preflight/src/preflight.rs

@@ -16,6 +16,8 @@ use std::convert::{TryFrom, TryInto};
 use std::iter::FromIterator;
 use std::rc::Rc;
 
+use crate::CResourceConfig;
+
 pub(crate) struct RestorePreamble {
     pub(crate) transaction_data: SorobanTransactionData,
     pub(crate) min_fee: i64,
@@ -40,6 +42,7 @@ pub(crate) fn preflight_invoke_hf_op(
     invoke_hf_op: InvokeHostFunctionOp,
     source_account: AccountId,
     ledger_info: LedgerInfo,
+    resource_config: CResourceConfig,
     enable_debug: bool,
 ) -> Result<PreflightResult> {
     let ledger_storage_rc = Rc::new(ledger_storage);
@@ -117,6 +120,7 @@ pub(crate) fn preflight_invoke_hf_op(
         &ledger_storage_rc,
         &storage,
         &budget,
+        resource_config,
         &diagnostic_events,
         &result,
         bucket_list_size,