Add second batch of pull request rework

- switch to ClientConnInterface
- use command type alias for map of commands
- add error return to command functions and handle in app.go
- inline formatJSON function in getAllAssets.go
- replace most panics with error returns
- remove error wrapping in listen.go and further down the line
- use strconv.ParseUint instead of ParseFloat
- use WithCancelCause in transact.go to grab and propagate error from
  go routine
- unmarshal and return []Asset in atb.GetAllAssets
- switch to rand package
- remove dependency to protobuf reflect package
- switch to sync.OnceValues for caching parser
- fixed typo in events sample connect.go

Signed-off-by: Stanislav Jakuschevskij <stas@two-giants.com>

asset-transfer-events/application-gateway-go/connect.go

@@ -31,7 +31,7 @@ const (
 func newGrpcConnection() *grpc.ClientConn {
 	certificatePEM, err := os.ReadFile(tlsCertPath)
 	if err != nil {
-		panic(fmt.Errorf("failed to read TLS certifcate file: %w", err))
+		panic(fmt.Errorf("failed to read TLS certificate file: %w", err))
 	}
 
 	certificate, err := identity.CertificateFromPEM(certificatePEM)

off_chain_data/application-go/app.go

@@ -1,9 +1,3 @@
-/*
- * Copyright 2024 IBM All Rights Reserved.
- *
- * SPDX-License-Identifier: Apache-2.0
- */
-
 package main
 
 import (
@@ -15,7 +9,9 @@ import (
 	"google.golang.org/grpc"
 )
 
-var allCommands = map[string]func(*grpc.ClientConn){
+type command func(grpc.ClientConnInterface) error
+
+var allCommands = map[string]command{
 	"getAllAssets": getAllAssets,
 	"transact":     transact,
 	"listen":       listen,
@@ -41,7 +37,10 @@ func main() {
 
 	for _, name := range commands {
 		command := allCommands[name]
-		command(client)
+
+		if err := command(client); err != nil {
+			panic(err)
+		}
 	}
 }
 

off_chain_data/application-go/connect.go

@@ -1,9 +1,3 @@
-/*
- * Copyright 2024 IBM All Rights Reserved.
- *
- * SPDX-License-Identifier: Apache-2.0
- */
-
 package main
 
 import (
@@ -69,7 +63,7 @@ func newGrpcConnection() *grpc.ClientConn {
 	return connection
 }
 
-func newConnectOptions(clientConnection *grpc.ClientConn) (identity.Identity, []client.ConnectOption) {
+func newConnectOptions(clientConnection grpc.ClientConnInterface) (identity.Identity, []client.ConnectOption) {
 	return newIdentity(), []client.ConnectOption{
 		client.WithSign(newSign()),
 		client.WithHash(hash.SHA256),

off_chain_data/application-go/contract/contract.go

@@ -1,12 +1,7 @@
-/*
- * Copyright 2024 IBM All Rights Reserved.
- *
- * SPDX-License-Identifier: Apache-2.0
- */
 package contract
 
 import (
-	"fmt"
+	"encoding/json"
 	"strconv"
 
 	"github.com/hyperledger/fabric-gateway/pkg/client"
@@ -30,7 +25,7 @@ func (atb *AssetTransferBasic) CreateAsset(anAsset Asset) error {
 			anAsset.Owner,
 			strconv.FormatUint(anAsset.AppraisedValue, 10),
 		)); err != nil {
-		return fmt.Errorf("in CreateAsset: %w", err)
+		return err
 	}
 	return nil
 }
@@ -44,7 +39,7 @@ func (atb *AssetTransferBasic) TransferAsset(id, newOwner string) (string, error
 		),
 	)
 	if err != nil {
-		return "", fmt.Errorf("in TransferAsset: %w", err)
+		return "", err
 	}
 
 	return string(result), nil
@@ -57,15 +52,25 @@ func (atb *AssetTransferBasic) DeleteAsset(id string) error {
 			id,
 		),
 	); err != nil {
-		return fmt.Errorf("in DeleteAsset: %w", err)
+		return err
 	}
 	return nil
 }
 
-func (atb *AssetTransferBasic) GetAllAssets() ([]byte, error) {
-	result, err := atb.contract.Evaluate("GetAllAssets")
+func (atb *AssetTransferBasic) GetAllAssets() ([]Asset, error) {
+	assetsRaw, err := atb.contract.Evaluate("GetAllAssets")
 	if err != nil {
-		return nil, fmt.Errorf("in GetAllAssets: %w", err)
+		return nil, err
 	}
-	return result, nil
+
+	if len(assetsRaw) == 0 {
+		return []Asset{}, nil
+	}
+
+	var assets []Asset
+	if err := json.Unmarshal(assetsRaw, &assets); err != nil {
+		return nil, err
+	}
+
+	return assets, nil
 }

off_chain_data/application-go/contract/model.go

@@ -1,8 +1,3 @@
-/*
- * Copyright 2024 IBM All Rights Reserved.
- *
- * SPDX-License-Identifier: Apache-2.0
- */
 package contract
 
 type Asset struct {

off_chain_data/application-go/getAllAssets.go

@@ -1,13 +1,6 @@
-/*
- * Copyright 2024 IBM All Rights Reserved.
- *
- * SPDX-License-Identifier: Apache-2.0
- */
-
 package main
 
 import (
-	"bytes"
 	"encoding/json"
 	"fmt"
 	atb "offchaindata/contract"
@@ -16,11 +9,11 @@ import (
 	"google.golang.org/grpc"
 )
 
-func getAllAssets(clientConnection *grpc.ClientConn) {
+func getAllAssets(clientConnection grpc.ClientConnInterface) error {
 	id, options := newConnectOptions(clientConnection)
 	gateway, err := client.Connect(id, options...)
 	if err != nil {
-		panic(err)
+		return err
 	}
 	defer gateway.Close()
 
@@ -28,21 +21,15 @@ func getAllAssets(clientConnection *grpc.ClientConn) {
 	smartContract := atb.NewAssetTransferBasic(contract)
 	assets, err := smartContract.GetAllAssets()
 	if err != nil {
-		panic(err)
+		return err
 	}
 
-	if len(assets) == 0 {
-		fmt.Println("no assets")
-		return
+	assetsJSONformatted, err := json.MarshalIndent(assets, "", "  ")
+	if err != nil {
+		return err
 	}
 
-	fmt.Println(formatJSON(assets))
-}
-
-func formatJSON(data []byte) string {
-	var result bytes.Buffer
-	if err := json.Indent(&result, data, "", "  "); err != nil {
-		panic(fmt.Errorf("failed to parse JSON: %w", err))
-	}
-	return result.String()
+	fmt.Println(assetsJSONformatted)
+
+	return nil
 }

off_chain_data/application-go/listen.go

@@ -14,11 +14,11 @@ import (
 	"google.golang.org/grpc"
 )
 
-func listen(clientConnection *grpc.ClientConn) {
+func listen(clientConnection grpc.ClientConnInterface) error {
 	id, options := newConnectOptions(clientConnection)
 	gateway, err := client.Connect(id, options...)
 	if err != nil {
-		panic(err)
+		return err
 	}
 	defer func() {
 		gateway.Close()
@@ -28,7 +28,7 @@ func listen(clientConnection *grpc.ClientConn) {
 	checkpointFile := envOrDefault("CHECKPOINT_FILE", "checkpoint.json")
 	checkpointer, err := client.NewFileCheckpointer(checkpointFile)
 	if err != nil {
-		panic(err)
+		return err
 	}
 	defer func() {
 		checkpointer.Close()
@@ -57,7 +57,7 @@ func listen(clientConnection *grpc.ClientConn) {
 		client.WithCheckpoint(checkpointer),
 	)
 	if err != nil {
-		panic(err)
+		return err
 	}
 
 	for blockProto := range blocks {
@@ -69,12 +69,12 @@ func listen(clientConnection *grpc.ClientConn) {
 		}
 
 		if err := aBlockProcessor.process(); err != nil {
-			fmt.Println("\033[31m[ERROR]\033[0m", err)
-			return
+			return err
 		}
 	}
 
 	fmt.Println("\nShutting down listener gracefully...")
+	return nil
 }
 
 type blockProcessor struct {
@@ -85,39 +85,37 @@ type blockProcessor struct {
 }
 
 func (b *blockProcessor) process() error {
-	funcName := "Process"
-
 	fmt.Println("\nReceived block", b.parsedBlock.Number())
 
 	validTransactions, err := b.validTransactions()
 	if err != nil {
-		return fmt.Errorf("in %s: %w", funcName, err)
+		return err
 	}
 
 	for _, validTransaction := range validTransactions {
-		aTransaction := transactionProcessor{
+		txProcessor := transactionProcessor{
 			b.parsedBlock.Number(),
 			validTransaction,
-			// TODO use pointer to parent and get blockNumber, store and channelName from parent
+			// TODO use reference to parent and get blockNumber, store and channelName from parent
 			b.writeToStore,
 			b.channelName,
 		}
-		if err := aTransaction.process(); err != nil {
-			return fmt.Errorf("in %s: %w", funcName, err)
+		if err := txProcessor.process(); err != nil {
+			return err
 		}
 
 		channelHeader, err := validTransaction.ChannelHeader()
 		if err != nil {
-			return fmt.Errorf("in %s: %w", funcName, err)
+			return err
 		}
 		transactionID := channelHeader.GetTxId()
 		if err := b.checkpointer.CheckpointTransaction(b.parsedBlock.Number(), transactionID); err != nil {
-			return fmt.Errorf("in %s: %w", funcName, err)
+			return err
 		}
 	}
 
 	if err := b.checkpointer.CheckpointBlock(b.parsedBlock.Number()); err != nil {
-		return fmt.Errorf("in %s: %w", funcName, err)
+		return err
 	}
 
 	return nil
@@ -127,7 +125,7 @@ func (b *blockProcessor) validTransactions() ([]*parser.Transaction, error) {
 	result := []*parser.Transaction{}
 	newTransactions, err := b.getNewTransactions()
 	if err != nil {
-		return nil, fmt.Errorf("in validTransactions: %w", err)
+		return nil, err
 	}
 
 	for _, transaction := range newTransactions {
@@ -139,11 +137,9 @@ func (b *blockProcessor) validTransactions() ([]*parser.Transaction, error) {
 }
 
 func (b *blockProcessor) getNewTransactions() ([]*parser.Transaction, error) {
-	funcName := "getNewTransactions"
-
 	transactions, err := b.parsedBlock.Transactions()
 	if err != nil {
-		return nil, fmt.Errorf("in %s: %w", funcName, err)
+		return nil, err
 	}
 
 	lastTransactionID := b.checkpointer.TransactionID()
@@ -155,24 +151,22 @@ func (b *blockProcessor) getNewTransactions() ([]*parser.Transaction, error) {
 	// Ignore transactions up to the last processed transaction ID
 	lastProcessedIndex, err := b.findLastProcessedIndex()
 	if err != nil {
-		return nil, fmt.Errorf("in %s: %w", funcName, err)
+		return nil, err
 	}
 	return transactions[lastProcessedIndex+1:], nil
 }
 
 func (b *blockProcessor) findLastProcessedIndex() (int, error) {
-	funcName := "findLastProcessedIndex"
-
 	transactions, err := b.parsedBlock.Transactions()
 	if err != nil {
-		return 0, fmt.Errorf("in %s: %w", funcName, err)
+		return 0, err
 	}
 
 	blockTransactionIDs := []string{}
 	for _, transaction := range transactions {
 		channelHeader, err := transaction.ChannelHeader()
 		if err != nil {
-			return 0, fmt.Errorf("in %s: %w", funcName, err)
+			return 0, err
 		}
 		blockTransactionIDs = append(blockTransactionIDs, channelHeader.GetTxId())
 	}
@@ -204,17 +198,15 @@ type transactionProcessor struct {
 }
 
 func (t *transactionProcessor) process() error {
-	funcName := "process"
-
 	channelHeader, err := t.transaction.ChannelHeader()
 	if err != nil {
-		return fmt.Errorf("in %s: %w", funcName, err)
+		return err
 	}
 	transactionID := channelHeader.GetTxId()
 
 	writes, err := t.writes()
 	if err != nil {
-		return fmt.Errorf("in %s: %w", funcName, err)
+		return err
 	}
 
 	if len(writes) == 0 {
@@ -229,25 +221,24 @@ func (t *transactionProcessor) process() error {
 		TransactionID: transactionID,
 		Writes:        writes,
 	}); err != nil {
-		return fmt.Errorf("in %s: %w", funcName, err)
+		return err
 	}
 
 	return nil
 }
 
 func (t *transactionProcessor) writes() ([]write, error) {
-	funcName := "writes"
 	// TODO this entire code should live in the parser and just return the kvWrite which
 	// we then map to write and return
 	channelHeader, err := t.transaction.ChannelHeader()
 	if err != nil {
-		return nil, fmt.Errorf("in %s: %w", funcName, err)
+		return nil, err
 	}
 	t.channelName = channelHeader.GetChannelId()
 
 	nsReadWriteSets, err := t.transaction.NamespaceReadWriteSets()
 	if err != nil {
-		return nil, fmt.Errorf("in %s: %w", funcName, err)
+		return nil, err
 	}
 
 	nonSystemCCReadWriteSets := []*parser.NamespaceReadWriteSet{}
@@ -263,7 +254,7 @@ func (t *transactionProcessor) writes() ([]write, error) {
 
 		kvReadWriteSet, err := readWriteSet.ReadWriteSet()
 		if err != nil {
-			return nil, fmt.Errorf("in %s: %w", funcName, err)
+			return nil, err
 		}
 
 		for _, kvWrite := range kvReadWriteSet.GetWrites() {

off_chain_data/application-go/parser/block.go

@@ -1,19 +1,21 @@
 package parser
 
 import (
-	"fmt"
+	"sync"
 
 	"github.com/hyperledger/fabric-protos-go-apiv2/common"
 	"google.golang.org/protobuf/proto"
 )
 
 type Block struct {
-	block              *common.Block
-	cachedTransactions []*Transaction
+	block        *common.Block
+	transactions func() ([]*Transaction, error)
 }
 
 func ParseBlock(block *common.Block) *Block {
-	return &Block{block, nil}
+	result := &Block{block, nil}
+	result.transactions = sync.OnceValues(result.unmarshalTransactions)
+	return result
 }
 
 func (b *Block) Number() uint64 {
@@ -21,37 +23,34 @@ func (b *Block) Number() uint64 {
 }
 
 func (b *Block) Transactions() ([]*Transaction, error) {
-	if b.cachedTransactions != nil {
-		return b.cachedTransactions, nil
-	}
+	return b.transactions()
+}
 
-	funcName := "Transactions"
-	envelopes, err := b.unmarshalEnvelopesFromBlockData()
+func (b *Block) unmarshalTransactions() ([]*Transaction, error) {
+	envelopes, err := b.unmarshalEnvelopes()
 	if err != nil {
-		return nil, fmt.Errorf("in %s: %w", funcName, err)
+		return nil, err
 	}
 
 	commonPayloads, err := b.unmarshalPayloadsFrom(envelopes)
 	if err != nil {
-		return nil, fmt.Errorf("in %s: %w", funcName, err)
+		return nil, err
 	}
 
 	payloads, err := b.parse(commonPayloads)
 	if err != nil {
-		return nil, fmt.Errorf("in %s: %w", funcName, err)
+		return nil, err
 	}
 
-	b.cachedTransactions = b.createTransactionsFrom(payloads)
-
-	return b.cachedTransactions, nil
+	return b.createTransactionsFrom(payloads), nil
 }
 
-func (b *Block) unmarshalEnvelopesFromBlockData() ([]*common.Envelope, error) {
+func (b *Block) unmarshalEnvelopes() ([]*common.Envelope, error) {
 	result := []*common.Envelope{}
 	for _, blockData := range b.block.GetData().GetData() {
 		envelope := &common.Envelope{}
 		if err := proto.Unmarshal(blockData, envelope); err != nil {
-			return nil, fmt.Errorf("in unmarshalEnvelopesFromBlockData: %w", err)
+			return nil, err
 		}
 		result = append(result, envelope)
 	}
@@ -63,7 +62,7 @@ func (*Block) unmarshalPayloadsFrom(envelopes []*common.Envelope) ([]*common.Pay
 	for _, envelope := range envelopes {
 		commonPayload := &common.Payload{}
 		if err := proto.Unmarshal(envelope.GetPayload(), commonPayload); err != nil {
-			return nil, fmt.Errorf("in unmarshalPayloadsFrom: %w", err)
+			return nil, err
 		}
 		result = append(result, commonPayload)
 	}
@@ -71,8 +70,6 @@ func (*Block) unmarshalPayloadsFrom(envelopes []*common.Envelope) ([]*common.Pay
 }
 
 func (b *Block) parse(commonPayloads []*common.Payload) ([]*payload, error) {
-	funcName := "parse"
-
 	validationCodes := b.block.GetMetadata().GetMetadata()[common.BlockMetadataIndex_TRANSACTIONS_FILTER]
 
 	result := []*payload{}
@@ -82,7 +79,7 @@ func (b *Block) parse(commonPayloads []*common.Payload) ([]*payload, error) {
 		payload := parsePayload(commonPayload, int32(statusCode))
 		is, err := payload.isEndorserTransaction()
 		if err != nil {
-			return nil, fmt.Errorf("in %s: %w", funcName, err)
+			return nil, err
 		}
 		if is {
 			result = append(result, payload)

off_chain_data/application-go/parser/block_test.go

@@ -10,7 +10,6 @@ import (
 	"github.com/hyperledger/fabric-protos-go-apiv2/ledger/rwset/kvrwset"
 	"github.com/hyperledger/fabric-protos-go-apiv2/peer"
 	"google.golang.org/protobuf/proto"
-	"google.golang.org/protobuf/reflect/protoreflect"
 )
 
 func Test_GetReadWriteSetsFromEndorserTransaction(t *testing.T) {
@@ -128,7 +127,7 @@ func nsReadWriteSetFake() (*rwset.NsReadWriteSet, string, atb.Asset) {
 	return result, expectedNamespace, expectedAsset
 }
 
-func protoMarshalOrPanic(v protoreflect.ProtoMessage) []byte {
+func protoMarshalOrPanic(v proto.Message) []byte {
 	result, err := proto.Marshal(v)
 	if err != nil {
 		panic(err)

off_chain_data/application-go/parser/endorserTransaction.go

@@ -1,7 +1,7 @@
 package parser
 
 import (
-	"fmt"
+	"sync"
 
 	"github.com/hyperledger/fabric-protos-go-apiv2/ledger/rwset"
 	"github.com/hyperledger/fabric-protos-go-apiv2/peer"
@@ -9,49 +9,43 @@ import (
 )
 
 type endorserTransaction struct {
-	transaction         *peer.Transaction
-	cachedReadWriteSets []*readWriteSet
+	transaction   *peer.Transaction
+	readWriteSets func() ([]*readWriteSet, error)
 }
 
 func parseEndorserTransaction(transaction *peer.Transaction) *endorserTransaction {
-	return &endorserTransaction{transaction, nil}
+	result := &endorserTransaction{transaction, nil}
+	result.readWriteSets = sync.OnceValues(result.unmarshalReadWriteSets)
+	return result
 }
 
-func (p *endorserTransaction) readWriteSets() ([]*readWriteSet, error) {
-	funcName := "readWriteSets"
-
-	if p.cachedReadWriteSets != nil {
-		return p.cachedReadWriteSets, nil
-	}
-
+func (p *endorserTransaction) unmarshalReadWriteSets() ([]*readWriteSet, error) {
 	chaincodeActionPayloads, err := p.unmarshalChaincodeActionPayloads()
 	if err != nil {
-		return nil, fmt.Errorf("in %s: %w", funcName, err)
+		return nil, err
 	}
 
 	chaincodeEndorsedActions, err := p.extractChaincodeEndorsedActionsFrom(chaincodeActionPayloads)
 	if err != nil {
-		return nil, fmt.Errorf("in %s: %w", funcName, err)
+		return nil, err
 	}
 
 	proposalResponsePayloads, err := p.unmarshalProposalResponsePayloadsFrom(chaincodeEndorsedActions)
 	if err != nil {
-		return nil, fmt.Errorf("in %s: %w", funcName, err)
+		return nil, err
 	}
 
 	chaincodeActions, err := p.unmarshalChaincodeActionsFrom(proposalResponsePayloads)
 	if err != nil {
-		return nil, fmt.Errorf("in %s: %w", funcName, err)
+		return nil, err
 	}
 
 	txReadWriteSets, err := p.unmarshalTxReadWriteSetsFrom(chaincodeActions)
 	if err != nil {
-		return nil, fmt.Errorf("in %s: %w", funcName, err)
+		return nil, err
 	}
 
-	p.cachedReadWriteSets = p.parseReadWriteSets(txReadWriteSets)
-
-	return p.cachedReadWriteSets, nil
+	return p.parseReadWriteSets(txReadWriteSets), nil
 }
 
 func (p *endorserTransaction) unmarshalChaincodeActionPayloads() ([]*peer.ChaincodeActionPayload, error) {
@@ -59,7 +53,7 @@ func (p *endorserTransaction) unmarshalChaincodeActionPayloads() ([]*peer.Chainc
 	for _, transactionAction := range p.transaction.GetActions() {
 		chaincodeActionPayload := &peer.ChaincodeActionPayload{}
 		if err := proto.Unmarshal(transactionAction.GetPayload(), chaincodeActionPayload); err != nil {
-			return nil, fmt.Errorf("in unmarshalChaincodeActionPayloads: %w", err)
+			return nil, err
 		}
 
 		result = append(result, chaincodeActionPayload)
@@ -80,7 +74,7 @@ func (*endorserTransaction) unmarshalProposalResponsePayloadsFrom(chaincodeEndor
 	for _, endorsedAction := range chaincodeEndorsedActions {
 		proposalResponsePayload := &peer.ProposalResponsePayload{}
 		if err := proto.Unmarshal(endorsedAction.GetProposalResponsePayload(), proposalResponsePayload); err != nil {
-			return nil, fmt.Errorf("in unmarshalProposalResponsePayloadsFrom: %w", err)
+			return nil, err
 		}
 		result = append(result, proposalResponsePayload)
 	}
@@ -92,7 +86,7 @@ func (*endorserTransaction) unmarshalChaincodeActionsFrom(proposalResponsePayloa
 	for _, proposalResponsePayload := range proposalResponsePayloads {
 		chaincodeAction := &peer.ChaincodeAction{}
 		if err := proto.Unmarshal(proposalResponsePayload.GetExtension(), chaincodeAction); err != nil {
-			return nil, fmt.Errorf("in unmarshalChaincodeActionsFrom: %w", err)
+			return nil, err
 		}
 		result = append(result, chaincodeAction)
 	}
@@ -104,7 +98,7 @@ func (*endorserTransaction) unmarshalTxReadWriteSetsFrom(chaincodeActions []*pee
 	for _, chaincodeAction := range chaincodeActions {
 		txReadWriteSet := &rwset.TxReadWriteSet{}
 		if err := proto.Unmarshal(chaincodeAction.GetResults(), txReadWriteSet); err != nil {
-			return nil, fmt.Errorf("in unmarshalTxReadWriteSetsFrom: %w", err)
+			return nil, err
 		}
 		result = append(result, txReadWriteSet)
 	}

off_chain_data/application-go/parser/namespaceReadWriteSet.go

@@ -1,7 +1,7 @@
 package parser
 
 import (
-	"fmt"
+	"sync"
 
 	"github.com/hyperledger/fabric-protos-go-apiv2/ledger/rwset"
 	"github.com/hyperledger/fabric-protos-go-apiv2/ledger/rwset/kvrwset"
@@ -9,12 +9,14 @@ import (
 )
 
 type NamespaceReadWriteSet struct {
-	nsReadWriteSet     *rwset.NsReadWriteSet
-	cachedReadWriteSet *kvrwset.KVRWSet
+	nsReadWriteSet *rwset.NsReadWriteSet
+	readWriteSet   func() (*kvrwset.KVRWSet, error)
 }
 
 func parseNamespaceReadWriteSet(nsRwSet *rwset.NsReadWriteSet) *NamespaceReadWriteSet {
-	return &NamespaceReadWriteSet{nsRwSet, nil}
+	result := &NamespaceReadWriteSet{nsRwSet, nil}
+	result.readWriteSet = sync.OnceValues(result.unmarshalReadWriteSet)
+	return result
 }
 
 func (p *NamespaceReadWriteSet) Namespace() string {
@@ -22,14 +24,14 @@ func (p *NamespaceReadWriteSet) Namespace() string {
 }
 
 func (p *NamespaceReadWriteSet) ReadWriteSet() (*kvrwset.KVRWSet, error) {
-	if p.cachedReadWriteSet != nil {
-		return p.cachedReadWriteSet, nil
-	}
-
-	p.cachedReadWriteSet = &kvrwset.KVRWSet{}
-	if err := proto.Unmarshal(p.nsReadWriteSet.GetRwset(), p.cachedReadWriteSet); err != nil {
-		return nil, fmt.Errorf("in ReadWriteSet: %w", err)
-	}
-
-	return p.cachedReadWriteSet, nil
+	return p.readWriteSet()
+}
+
+func (p *NamespaceReadWriteSet) unmarshalReadWriteSet() (*kvrwset.KVRWSet, error) {
+	result := &kvrwset.KVRWSet{}
+	if err := proto.Unmarshal(p.nsReadWriteSet.GetRwset(), result); err != nil {
+		return nil, err
+	}
+
+	return result, nil
 }

off_chain_data/application-go/parser/payload.go

@@ -2,6 +2,7 @@ package parser
 
 import (
 	"fmt"
+	"sync"
 
 	"github.com/hyperledger/fabric-protos-go-apiv2/common"
 	"github.com/hyperledger/fabric-protos-go-apiv2/peer"
@@ -9,46 +10,42 @@ import (
 )
 
 type payload struct {
-	commonPayload       *common.Payload
-	statusCode          int32
-	cachedChannelHeader *common.ChannelHeader
+	commonPayload *common.Payload
+	statusCode    int32
+	channelHeader func() (*common.ChannelHeader, error)
 }
 
 func parsePayload(commonPayload *common.Payload, statusCode int32) *payload {
-	return &payload{commonPayload, statusCode, nil}
+	result := &payload{commonPayload, statusCode, nil}
+	result.channelHeader = sync.OnceValues(result.unmarshalChannelHeader)
+	return result
 }
 
-func (p *payload) channelHeader() (*common.ChannelHeader, error) {
-	if p.cachedChannelHeader != nil {
-		return p.cachedChannelHeader, nil
+func (p *payload) unmarshalChannelHeader() (*common.ChannelHeader, error) {
+	result := &common.ChannelHeader{}
+	if err := proto.Unmarshal(p.commonPayload.GetHeader().GetChannelHeader(), result); err != nil {
+		return nil, err
 	}
 
-	p.cachedChannelHeader = &common.ChannelHeader{}
-	if err := proto.Unmarshal(p.commonPayload.GetHeader().GetChannelHeader(), p.cachedChannelHeader); err != nil {
-		return nil, fmt.Errorf("in channelHeader: %w", err)
-	}
-
-	return p.cachedChannelHeader, nil
+	return result, nil
 }
 
 func (p *payload) endorserTransaction() (*endorserTransaction, error) {
-	funcName := "endorserTransaction"
-
 	is, err := p.isEndorserTransaction()
 	if err != nil {
-		return nil, fmt.Errorf("in %s: %w", funcName, err)
+		return nil, err
 	}
 	if !is {
 		channelHeader, err := p.channelHeader()
 		if err != nil {
-			return nil, fmt.Errorf("in %s: %w", funcName, err)
+			return nil, err
 		}
 		return nil, fmt.Errorf("unexpected payload type: %d", channelHeader.GetType())
 	}
 
 	result := &peer.Transaction{}
 	if err := proto.Unmarshal(p.commonPayload.GetData(), result); err != nil {
-		return nil, fmt.Errorf("in %s: %w", funcName, err)
+		return nil, err
 	}
 
 	return parseEndorserTransaction(result), nil
@@ -57,7 +54,7 @@ func (p *payload) endorserTransaction() (*endorserTransaction, error) {
 func (p *payload) isEndorserTransaction() (bool, error) {
 	channelHeader, err := p.channelHeader()
 	if err != nil {
-		return false, fmt.Errorf("in isEndorserTransaction: %w", err)
+		return false, err
 	}
 
 	return channelHeader.GetType() == int32(common.HeaderType_ENDORSER_TRANSACTION), nil

off_chain_data/application-go/parser/transaction.go

@@ -1,8 +1,6 @@
 package parser
 
 import (
-	"fmt"
-
 	"github.com/hyperledger/fabric-protos-go-apiv2/common"
 )
 
@@ -19,16 +17,14 @@ func (t *Transaction) ChannelHeader() (*common.ChannelHeader, error) {
 }
 
 func (t *Transaction) NamespaceReadWriteSets() ([]*NamespaceReadWriteSet, error) {
-	funcName := "NamespaceReadWriteSets"
-
 	endorserTransaction, err := t.payload.endorserTransaction()
 	if err != nil {
-		return nil, fmt.Errorf("in %s: %w", funcName, err)
+		return nil, err
 	}
 
 	txReadWriteSets, err := endorserTransaction.readWriteSets()
 	if err != nil {
-		return nil, fmt.Errorf("in %s: %w", funcName, err)
+		return nil, err
 	}
 
 	result := []*NamespaceReadWriteSet{}

off_chain_data/application-go/store.go

@@ -4,7 +4,6 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
-	"math"
 	"os"
 	"strconv"
 	"strings"
@@ -41,17 +40,15 @@ type write struct {
 // Apply writes for a given transaction to off-chain data store, ideally in a single operation for fault tolerance.
 // This implementation just writes to a file.
 func applyWritesToOffChainStore(data ledgerUpdate) error {
-	funcName := "applyWritesToOffChainStore"
-
 	if err := simulateFailureIfRequired(); err != nil {
-		return fmt.Errorf("in %s: %w", funcName, err)
+		return err
 	}
 
 	writes := []string{}
 	for _, write := range data.Writes {
 		marshaled, err := json.Marshal(write)
 		if err != nil {
-			return fmt.Errorf("in %s: %w", funcName, err)
+			return err
 		}
 
 		writes = append(writes, string(marshaled))
@@ -59,16 +56,16 @@ func applyWritesToOffChainStore(data ledgerUpdate) error {
 
 	f, err := os.OpenFile(storeFile, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
 	if err != nil {
-		return fmt.Errorf("in %s: %w", funcName, err)
+		return err
 	}
 
 	if _, err := f.Write([]byte(strings.Join(writes, "\n") + "\n")); err != nil {
 		f.Close()
-		return fmt.Errorf("in %s: %w", funcName, err)
+		return err
 	}
 
 	if err := f.Close(); err != nil {
-		return fmt.Errorf("in %s: %w", funcName, err)
+		return err
 	}
 
 	return nil
@@ -87,13 +84,8 @@ func simulateFailureIfRequired() error {
 
 func getSimulatedFailureCount() uint {
 	valueAsString := envOrDefault("SIMULATED_FAILURE_COUNT", "0")
-	valueAsFloat, err := strconv.ParseFloat(valueAsString, 64)
+	result, err := strconv.ParseUint(valueAsString, 10, 0)
 	if err != nil {
-		panic(err)
-	}
-
-	result := math.Floor(valueAsFloat)
-	if valueAsFloat < 0 {
 		panic(fmt.Errorf("invalid SIMULATED_FAILURE_COUNT value: %s", valueAsString))
 	}
 

off_chain_data/application-go/transact.go

@@ -1,9 +1,9 @@
 package main
 
 import (
-	"crypto/rand"
+	"context"
 	"fmt"
-	"math/big"
+	"math/rand/v2"
 	"sync"
 
 	atb "offchaindata/contract"
@@ -15,11 +15,11 @@ import (
 
 var owners = []string{"alice", "bob", "charlie"}
 
-func transact(clientConnection *grpc.ClientConn) {
+func transact(clientConnection grpc.ClientConnInterface) error {
 	id, options := newConnectOptions(clientConnection)
 	gateway, err := client.Connect(id, options...)
 	if err != nil {
-		panic((err))
+		return err
 	}
 	defer func() {
 		gateway.Close()
@@ -30,7 +30,11 @@ func transact(clientConnection *grpc.ClientConn) {
 
 	smartContract := atb.NewAssetTransferBasic(contract)
 	app := newTransactApp(smartContract)
-	app.run()
+	if err := app.run(); err != nil {
+		return err
+	}
+
+	return nil
 }
 
 type transactApp struct {
@@ -42,90 +46,94 @@ func newTransactApp(smartContract *atb.AssetTransferBasic) *transactApp {
 	return &transactApp{smartContract, 10}
 }
 
-func (t *transactApp) run() {
+func (t *transactApp) run() error {
+	ctx, cancel := context.WithCancelCause(context.Background())
+	defer cancel(nil)
+
 	var wg sync.WaitGroup
 
-	for i := 0; i < t.batchSize; i++ {
+	for range t.batchSize {
 		wg.Add(1)
 		go func() {
 			defer wg.Done()
 
-			if err := t.transact(); err != nil {
-				fmt.Println("\033[31m[ERROR]\033[0m", err)
+			select {
+			case <-ctx.Done():
 				return
+			default:
+				if err := t.transact(); err != nil {
+					cancel(err)
+					return
+				}
 			}
 		}()
 	}
 
 	wg.Wait()
+
+	if err := context.Cause(ctx); err != nil {
+		return err
+	}
+
+	return nil
 }
 
 func (t *transactApp) transact() error {
-	funcName := "transact"
-
-	anAsset := newAsset()
-
-	err := t.smartContract.CreateAsset(anAsset)
+	anAsset, err := newAsset()
 	if err != nil {
-		return fmt.Errorf("in %s: %w", funcName, err)
+		return err
+	}
+
+	if err := t.smartContract.CreateAsset(anAsset); err != nil {
+		return err
 	}
 	fmt.Println("Created asset", anAsset.ID)
 
 	// Transfer randomly 1 in 2 assets to a new owner.
-	if randomInt(2) == 0 {
+	if rand.N(2) == 0 {
 		newOwner := differentElement(owners, anAsset.Owner)
 		oldOwner, err := t.smartContract.TransferAsset(anAsset.ID, newOwner)
 		if err != nil {
-			return fmt.Errorf("in %s: %w", funcName, err)
+			return err
 		}
 		fmt.Printf("Transferred asset %s from %s to %s\n", anAsset.ID, oldOwner, newOwner)
 	}
 
 	// Delete randomly 1 in 4 created assets.
-	if randomInt(4) == 0 {
-		err := t.smartContract.DeleteAsset(anAsset.ID)
-		if err != nil {
-			return fmt.Errorf("in %s: %w", funcName, err)
+	if rand.N(4) == 0 {
+		if err := t.smartContract.DeleteAsset(anAsset.ID); err != nil {
+			return err
 		}
 		fmt.Println("Deleted asset", anAsset.ID)
 	}
+
 	return nil
 }
 
-func newAsset() atb.Asset {
+func newAsset() (atb.Asset, error) {
 	id, err := uuid.NewRandom()
 	if err != nil {
-		panic(err)
+		return atb.Asset{}, err
 	}
 
 	return atb.Asset{
 		ID:             id.String(),
 		Color:          randomElement([]string{"red", "green", "blue"}),
-		Size:           uint64(randomInt(10) + 1),
+		Size:           uint64(rand.N(10) + 1),
 		Owner:          randomElement(owners),
-		AppraisedValue: uint64(randomInt(1000) + 1),
-	}
+		AppraisedValue: uint64(rand.N(1000) + 1),
+	}, nil
 }
 
 // Pick a random element from an array.
 func randomElement(values []string) string {
-	result := values[randomInt(len(values))]
+	result := values[rand.N(len(values))]
 	return result
 }
 
-// Generate a random integer in the range 0 to max - 1.
-func randomInt(max int) int {
-	result, err := rand.Int(rand.Reader, big.NewInt(int64(max)))
-	if err != nil {
-		panic(err)
-	}
-
-	return int(result.Int64())
-}
-
 // Pick a random element from an array, excluding the current value.
 func differentElement(values []string, currentValue string) string {
-	candidateValues := []string{}
+	var candidateValues []string
 	for _, v := range values {
 		if v != currentValue {
 			candidateValues = append(candidateValues, v)