node: allow registration of custom reactors while creating node (#3771)

* change invocation of NewNode across

* custom reactor name are prefixed with CUSTOM_

* upgate changelog pending

* improve comments

* node: refactor NewNode to use functional options

node/node.go

@@ -47,6 +47,10 @@ import (
 	"github.com/tendermint/tendermint/version"
 )
 
+// CustomReactorNamePrefix is a prefix for all custom reactors to prevent
+// clashes with built-in reactors.
+const CustomReactorNamePrefix = "CUSTOM_"
+
 //------------------------------------------------------------------------------
 
 // DBContext specifies config information for loading a new DB.
@@ -136,6 +140,18 @@ func DefaultMetricsProvider(config *cfg.InstrumentationConfig) MetricsProvider {
 	}
 }
 
+// Option sets a parameter for the node.
+type Option func(*Node)
+
+// CustomReactors allows you to add custom reactors to the node's Switch.
+func CustomReactors(reactors map[string]p2p.Reactor) Option {
+	return func(n *Node) {
+		for name, reactor := range reactors {
+			n.sw.AddReactor(CustomReactorNamePrefix+name, reactor)
+		}
+	}
+}
+
 //------------------------------------------------------------------------------
 
 // Node is the highest level interface to a full Tendermint node.
@@ -433,6 +449,7 @@ func createSwitch(config *cfg.Config,
 	sw.AddReactor("BLOCKCHAIN", bcReactor)
 	sw.AddReactor("CONSENSUS", consensusReactor)
 	sw.AddReactor("EVIDENCE", evidenceReactor)
+
 	sw.SetNodeInfo(nodeInfo)
 	sw.SetNodeKey(nodeKey)
 
@@ -495,7 +512,8 @@ func NewNode(config *cfg.Config,
 	genesisDocProvider GenesisDocProvider,
 	dbProvider DBProvider,
 	metricsProvider MetricsProvider,
-	logger log.Logger) (*Node, error) {
+	logger log.Logger,
+	options ...Option) (*Node, error) {
 
 	blockStore, stateDB, err := initDBs(config, dbProvider)
 	if err != nil {
@@ -661,6 +679,11 @@ func NewNode(config *cfg.Config,
 		eventBus:         eventBus,
 	}
 	node.BaseService = *cmn.NewBaseService(logger, "Node", node)
+
+	for _, option := range options {
+		option(node)
+	}
+
 	return node, nil
 }