fix(client): persist reth blocks during ZFS snapshot prep so the head isn't lost

pkg/client/besu.go

@@ -103,3 +103,8 @@ func (s *besuSpec) RPCRollbackSpec() *RPCRollbackSpec {
 func (s *besuSpec) DefaultConfigFiles() map[string]string {
 	return nil
 }
+
+// SnapshotPrepareArgs returns nil; Besu needs no snapshot-only args.
+func (s *besuSpec) SnapshotPrepareArgs() []string {
+	return nil
+}

pkg/client/client.go

@@ -88,6 +88,9 @@ type Spec interface {
 	// Keys are target paths inside the container, values are file contents.
 	// Returns nil if no config files are needed.
 	DefaultConfigFiles() map[string]string
+
+	// SnapshotPrepareArgs returns args for the ZFS snapshot-prep container only (not per-test measurement); nil if none.
+	SnapshotPrepareArgs() []string
 }
 
 // Registry manages client specifications.

pkg/client/erigon.go

@@ -109,3 +109,8 @@ func (s *erigonSpec) RPCRollbackSpec() *RPCRollbackSpec {
 func (s *erigonSpec) DefaultConfigFiles() map[string]string {
 	return nil
 }
+
+// SnapshotPrepareArgs returns nil; Erigon needs no snapshot-only args.
+func (s *erigonSpec) SnapshotPrepareArgs() []string {
+	return nil
+}

pkg/client/ethrex.go

@@ -89,3 +89,8 @@ func (s *ethrexSpec) RPCRollbackSpec() *RPCRollbackSpec {
 func (s *ethrexSpec) DefaultConfigFiles() map[string]string {
 	return nil
 }
+
+// SnapshotPrepareArgs returns nil; Ethrex needs no snapshot-only args.
+func (s *ethrexSpec) SnapshotPrepareArgs() []string {
+	return nil
+}

pkg/client/geth.go

@@ -108,3 +108,8 @@ IdleTimeout = 120000000000 # 120s
 `,
 	}
 }
+
+// SnapshotPrepareArgs returns nil; Geth needs no snapshot-only args.
+func (s *gethSpec) SnapshotPrepareArgs() []string {
+	return nil
+}

pkg/client/nethermind.go

@@ -101,3 +101,8 @@ func (s *nethermindSpec) RPCRollbackSpec() *RPCRollbackSpec {
 func (s *nethermindSpec) DefaultConfigFiles() map[string]string {
 	return nil
 }
+
+// SnapshotPrepareArgs returns nil; Nethermind needs no snapshot-only args.
+func (s *nethermindSpec) SnapshotPrepareArgs() []string {
+	return nil
+}

pkg/client/nimbus.go

@@ -88,3 +88,8 @@ func (s *nimbusSpec) RPCRollbackSpec() *RPCRollbackSpec {
 func (s *nimbusSpec) DefaultConfigFiles() map[string]string {
 	return nil
 }
+
+// SnapshotPrepareArgs returns nil; Nimbus needs no snapshot-only args.
+func (s *nimbusSpec) SnapshotPrepareArgs() []string {
+	return nil
+}

pkg/client/reth.go

@@ -90,3 +90,11 @@ func (s *rethSpec) RPCRollbackSpec() *RPCRollbackSpec {
 func (s *rethSpec) DefaultConfigFiles() map[string]string {
 	return nil
 }
+
+// SnapshotPrepareArgs makes reth persist every block during snapshot prep so the pre-run head reaches disk (else the snapshot lags a block and tests hang SYNCING).
+func (s *rethSpec) SnapshotPrepareArgs() []string {
+	return []string{
+		"--engine.persistence-threshold=0",
+		"--engine.memory-block-buffer-target=0",
+	}
+}

pkg/runner/lifecycle.go

@@ -699,8 +699,25 @@ func (r *runner) runContainerLifecycle(
 	params.DataDirCfg = datadirCfg
 	params.UseDataDir = useDataDir
 
+	// Apply client-specific snapshot-prepare args to the initial (pre-run/snapshot) container only, scoped to ZFS container-recreate; per-test containers clone params.ContainerSpec and keep the base command.
+	createSpec := containerSpec
+
+	if prepareArgs := spec.SnapshotPrepareArgs(); len(prepareArgs) > 0 &&
+		r.cfg.FullConfig != nil &&
+		r.cfg.FullConfig.GetRollbackStrategy(instance) ==
+			config.RollbackStrategyContainerRecreate &&
+		datadirCfg != nil && datadirCfg.Method == "zfs" {
+		prepareSpec := *containerSpec
+		prepareSpec.Command = append(append([]string{}, cmd...), prepareArgs...)
+		createSpec = &prepareSpec
+
+		log.WithField("args", prepareArgs).Info(
+			"Applying snapshot-prepare args to initial (pre-run) container",
+		)
+	}
+
 	// Create container.
-	containerID, err := r.containerMgr.CreateContainer(ctx, containerSpec)
+	containerID, err := r.containerMgr.CreateContainer(ctx, createSpec)
 	if err != nil {
 		return fmt.Errorf("creating container: %w", err)
 	}