[NOD-381] Send transaction notifications to MQTT (#483)

* [NOD-381] Publish transaction messages to MQTT

* [NOD-381] Remove redundant variable

* [NOD-381] Send payload as string

* [NOD-381] Add Error handling

* [NOD-381] Respond with TransactionResponse

* [NOD-381] Use transactionResponse for notifications

* [NOD-381] Move code to appropriate places

* [NOD-381] Pass raw block instead of txId

* [NOD-381] Add comments to public functions

* [NOD-381] Remove print statement

* [NOD-381] Pass transaction instead of block; Use pointers so default will be nil;

* [NOD-381] Use pointers so value could be nil

* [NOD-381] Change variable name

* [NOD-381] Set QoS to 2

* [NOD-381] Move isConnected to MQTT, so client won't have to worry about it; General code refactors;

apiserver/apimodels/response_types.go

@@ -4,8 +4,8 @@ package apimodels
 type TransactionResponse struct {
 	TransactionHash         string                       `json:"transactionHash"`
 	TransactionID           string                       `json:"transactionId"`
-	AcceptingBlockHash      string                       `json:"acceptingBlockHash,omitempty"`
-	AcceptingBlockBlueScore uint64                       `json:"acceptingBlockBlueScore,omitempty"`
+	AcceptingBlockHash      *string                      `json:"acceptingBlockHash,omitempty"`
+	AcceptingBlockBlueScore *uint64                      `json:"acceptingBlockBlueScore,omitempty"`
 	SubnetworkID            string                       `json:"subnetworkId"`
 	LockTime                uint64                       `json:"lockTime"`
 	Gas                     uint64                       `json:"gas,omitempty"`

apiserver/controllers/common.go

@@ -9,18 +9,20 @@ import (
 
 func convertTxDBModelToTxResponse(tx *dbmodels.Transaction) *apimodels.TransactionResponse {
 	txRes := &apimodels.TransactionResponse{
-		TransactionHash:         tx.TransactionHash,
-		TransactionID:           tx.TransactionID,
-		AcceptingBlockHash:      tx.AcceptingBlock.BlockHash,
-		AcceptingBlockBlueScore: tx.AcceptingBlock.BlueScore,
-		SubnetworkID:            tx.Subnetwork.SubnetworkID,
-		LockTime:                tx.LockTime,
-		Gas:                     tx.Gas,
-		PayloadHash:             tx.PayloadHash,
-		Payload:                 hex.EncodeToString(tx.Payload),
-		Inputs:                  make([]*apimodels.TransactionInputResponse, len(tx.TransactionInputs)),
-		Outputs:                 make([]*apimodels.TransactionOutputResponse, len(tx.TransactionOutputs)),
-		Mass:                    tx.Mass,
+		TransactionHash: tx.TransactionHash,
+		TransactionID:   tx.TransactionID,
+		SubnetworkID:    tx.Subnetwork.SubnetworkID,
+		LockTime:        tx.LockTime,
+		Gas:             tx.Gas,
+		PayloadHash:     tx.PayloadHash,
+		Payload:         hex.EncodeToString(tx.Payload),
+		Inputs:          make([]*apimodels.TransactionInputResponse, len(tx.TransactionInputs)),
+		Outputs:         make([]*apimodels.TransactionOutputResponse, len(tx.TransactionOutputs)),
+		Mass:            tx.Mass,
+	}
+	if tx.AcceptingBlock != nil {
+		txRes.AcceptingBlockHash = &tx.AcceptingBlock.BlockHash
+		txRes.AcceptingBlockBlueScore = &tx.AcceptingBlock.BlueScore
 	}
 	for i, txOut := range tx.TransactionOutputs {
 		txRes.Outputs[i] = &apimodels.TransactionOutputResponse{

apiserver/controllers/transaction.go

@@ -89,12 +89,7 @@ func GetTransactionsByAddressHandler(address string, skip uint64, limit uint64)
 	}
 
 	txs := []*dbmodels.Transaction{}
-	query := db.
-		Joins("LEFT JOIN `transaction_outputs` ON `transaction_outputs`.`transaction_id` = `transactions`.`id`").
-		Joins("LEFT JOIN `addresses` AS `out_addresses` ON `out_addresses`.`id` = `transaction_outputs`.`address_id`").
-		Joins("LEFT JOIN `transaction_inputs` ON `transaction_inputs`.`transaction_id` = `transactions`.`id`").
-		Joins("LEFT JOIN `transaction_outputs` AS `inputs_outs` ON `inputs_outs`.`id` = `transaction_inputs`.`previous_transaction_output_id`").
-		Joins("LEFT JOIN `addresses` AS `in_addresses` ON `in_addresses`.`id` = `inputs_outs`.`address_id`").
+	query := joinTxInputsTxOutputsAndAddresses(db).
 		Where("`out_addresses`.`address` = ?", address).
 		Or("`in_addresses`.`address` = ?", address).
 		Limit(limit).
@@ -224,6 +219,15 @@ func GetUTXOsByAddressHandler(address string) (interface{}, error) {
 	return UTXOsResponses, nil
 }
 
+func joinTxInputsTxOutputsAndAddresses(query *gorm.DB) *gorm.DB {
+	return query.
+		Joins("LEFT JOIN `transaction_outputs` ON `transaction_outputs`.`transaction_id` = `transactions`.`id`").
+		Joins("LEFT JOIN `addresses` AS `out_addresses` ON `out_addresses`.`id` = `transaction_outputs`.`address_id`").
+		Joins("LEFT JOIN `transaction_inputs` ON `transaction_inputs`.`transaction_id` = `transactions`.`id`").
+		Joins("LEFT JOIN `transaction_outputs` AS `inputs_outs` ON `inputs_outs`.`id` = `transaction_inputs`.`previous_transaction_output_id`").
+		Joins("LEFT JOIN `addresses` AS `in_addresses` ON `in_addresses`.`id` = `inputs_outs`.`address_id`")
+}
+
 func addTxPreloadedFields(query *gorm.DB) *gorm.DB {
 	return query.Preload("AcceptingBlock").
 		Preload("Subnetwork").
@@ -274,3 +278,22 @@ func PostTransaction(requestBody []byte) error {
 
 	return nil
 }
+
+// GetTransactionsByIdsHandler finds transactions by the given transactionIds.
+func GetTransactionsByIdsHandler(db *gorm.DB, transactionIds []string) ([]*apimodels.TransactionResponse, error) {
+	var txs []*dbmodels.Transaction
+	query := joinTxInputsTxOutputsAndAddresses(db).
+		Where("`transactions`.`transaction_id` IN (?)", transactionIds)
+
+	dbResult := addTxPreloadedFields(query).Find(&txs)
+	dbErrors := dbResult.GetErrors()
+	if httpserverutils.HasDBError(dbErrors) {
+		return nil, httpserverutils.NewErrorFromDBErrors("Some errors were encountered when loading transactions from the database:", dbErrors)
+	}
+
+	txResponses := make([]*apimodels.TransactionResponse, len(txs))
+	for i, tx := range txs {
+		txResponses[i] = convertTxDBModelToTxResponse(tx)
+	}
+	return txResponses, nil
+}

apiserver/mqtt/mqtt.go

@@ -17,6 +17,10 @@ func GetClient() (mqtt.Client, error) {
 	return client, nil
 }
 
+func isConnected() bool {
+	return client != nil
+}
+
 // Connect initiates a connection to the MQTT server, if defined
 func Connect() error {
 	cfg := config.ActiveConfig()

apiserver/mqtt/transactions.go

@@ -0,0 +1,77 @@
+package mqtt
+
+import (
+	"encoding/json"
+	"fmt"
+	"github.com/daglabs/btcd/apiserver/apimodels"
+	"github.com/daglabs/btcd/apiserver/controllers"
+	"github.com/daglabs/btcd/btcjson"
+	"github.com/jinzhu/gorm"
+)
+
+// PublishTransactionsNotifications publishes notification for each transaction of the given block
+func PublishTransactionsNotifications(db *gorm.DB, rawTransactions []btcjson.TxRawResult) error {
+	if !isConnected() {
+		return nil
+	}
+
+	transactionIds := make([]string, len(rawTransactions))
+	for i, tx := range rawTransactions {
+		transactionIds[i] = tx.TxID
+	}
+
+	transactions, err := controllers.GetTransactionsByIdsHandler(db, transactionIds)
+	if err != nil {
+		return err
+	}
+
+	for _, transaction := range transactions {
+		err = publishTransactionNotifications(transaction)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func publishTransactionNotifications(transaction *apimodels.TransactionResponse) error {
+	addresses := uniqueAddressesForTransaction(transaction)
+	for _, address := range addresses {
+		err := publishTransactionNotificationForAddress(transaction, address)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func uniqueAddressesForTransaction(transaction *apimodels.TransactionResponse) []string {
+	addressesMap := make(map[string]struct{})
+	addresses := []string{}
+	for _, output := range transaction.Outputs {
+		if _, exists := addressesMap[output.Address]; !exists {
+			addresses = append(addresses, output.Address)
+			addressesMap[output.Address] = struct{}{}
+		}
+	}
+	return addresses
+}
+
+func publishTransactionNotificationForAddress(transaction *apimodels.TransactionResponse, address string) error {
+	payload, err := json.Marshal(transaction)
+	if err != nil {
+		return err
+	}
+
+	token := client.Publish(transactionsTopic(address), 2, false, payload)
+	token.Wait()
+	if token.Error() != nil {
+		return token.Error()
+	}
+
+	return nil
+}
+
+func transactionsTopic(address string) string {
+	return fmt.Sprintf("transactions/%s", address)
+}

apiserver/sync.go

@@ -3,6 +3,7 @@ package main
 import (
 	"bytes"
 	"encoding/hex"
+	"github.com/daglabs/btcd/apiserver/mqtt"
 	"strconv"
 	"strings"
 	"time"
@@ -298,6 +299,11 @@ func addBlock(client *jsonrpc.Client, rawBlock string, verboseBlock btcjson.GetB
 		return httpserverutils.NewErrorFromDBErrors("failed to update block: ", dbErrors)
 	}
 
+	err = mqtt.PublishTransactionsNotifications(dbTx, verboseBlock.RawTx)
+	if err != nil {
+		return err
+	}
+
 	dbTx.Commit()
 
 	// If the block was previously missing, remove it from