From 4e5ac3c716515f82d306587ee5ff13f7268ca6f6 Mon Sep 17 00:00:00 2001
From: Alejo Acosta <alejoacos@gmail.com>
Date: Tue, 17 Oct 2023 00:13:11 -0300
Subject: [PATCH] add support for node info persistence on file

---
 .gitignore       |  3 ++-
 p2p/node/api.go  |  3 ++-
 p2p/node/cid.go  | 38 ++++++++++++++++++++++++++++++++++++++
 p2p/node/node.go | 25 +++++++++++++++++++------
 4 files changed, 61 insertions(+), 8 deletions(-)

diff --git a/.gitignore b/.gitignore
index a5013fb8c8..afafe5f6e5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,4 +5,5 @@
 #   git config --global core.excludesfile ~/.gitignore_global
 
 *.key
-nodelogs
\ No newline at end of file
+nodelogs
+node.info
\ No newline at end of file
diff --git a/p2p/node/api.go b/p2p/node/api.go
index e1e5ee5795..778acfd52d 100644
--- a/p2p/node/api.go
+++ b/p2p/node/api.go
@@ -104,8 +104,9 @@ func (p *P2PNode) ListenForEvents() {
 		case evt := <-subAddrUpdated.Out():
 			if e, ok := evt.(event.EvtLocalAddressesUpdated); ok {
 				for _, addr := range e.Current {
-					fullAddr := fmt.Sprintf("%+v/p2p/%s", addr, p.ID().Pretty())
+					fullAddr := fmt.Sprintf("%+v/p2p/%s", addr.Address.String(), p.ID().Pretty())
 					log.Debugf("Advertised Address changed: %s", fullAddr)
+					saveNodeInfo("Advertised address: " + fullAddr)
 				}
 			}
 		case evt := <-subPeerConnected.Out():
diff --git a/p2p/node/cid.go b/p2p/node/cid.go
index 0915041745..38940e4228 100644
--- a/p2p/node/cid.go
+++ b/p2p/node/cid.go
@@ -1,6 +1,7 @@
 package node
 
 import (
+	"bufio"
 	"crypto/rand"
 	"os"
 
@@ -9,6 +10,11 @@ import (
 	"github.com/libp2p/go-libp2p/core/crypto"
 )
 
+const (
+	// file to store node's CID and listening address
+	nodeInfoFile = "node.info"
+)
+
 // Returns the private key stored in the file to be used to generate
 // the node's identity (CID)
 func getPrivKey(privKeyFile string) (crypto.PrivKey, error) {
@@ -52,3 +58,35 @@ func getPrivKey(privKeyFile string) (crypto.PrivKey, error) {
 	return privateKey, nil
 
 }
+
+// Utility function that synchronously writes the provided "info" string to the node.info file.
+// If the file doesn't exist, it creates it. Otherwise, it appends the new "info" as a new line.
+func saveNodeInfo(info string) {
+	go func() {
+		// Open file with O_APPEND flag to append data to the file or create the file if it doesn't exist.
+		f, err := os.OpenFile(nodeInfoFile, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
+		if err != nil {
+			log.Errorf("error opening node info file: %s", err)
+			return
+		}
+		defer f.Close()
+
+		// Use bufio for efficient writing
+		writer := bufio.NewWriter(f)
+		defer writer.Flush()
+
+		// Append new line and write to file
+		writer.WriteString(info + "\n")
+	}()
+}
+
+// utility function used to delete any existing node info file
+func deleteNodeInfoFile() error {
+	if _, err := os.Stat(nodeInfoFile); !os.IsNotExist(err) {
+		err := os.Remove(nodeInfoFile)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
diff --git a/p2p/node/node.go b/p2p/node/node.go
index 90d9f098bd..a41c9da039 100644
--- a/p2p/node/node.go
+++ b/p2p/node/node.go
@@ -10,7 +10,6 @@ import (
 	routedhost "github.com/libp2p/go-libp2p/p2p/host/routed"
 
 	"github.com/libp2p/go-libp2p"
-	dht "github.com/libp2p/go-libp2p-kad-dht"
 	kadht "github.com/libp2p/go-libp2p-kad-dht"
 	"github.com/libp2p/go-libp2p/core/host"
 
@@ -51,12 +50,11 @@ func NewNode(ctx context.Context) (*P2PNode, error) {
 
 	// list of options to instantiate the libp2p node
 	nodeOptions := []libp2p.Option{}
-
+	// use a private key for persistent identity
 	nodeOptions = append(nodeOptions, libp2p.Identity(privateKey))
-
+	// pass the ip address and port to listen on
 	sourceMultiAddr, _ := multiaddr.NewMultiaddr(fmt.Sprintf("/ip4/%s/tcp/%s", ipAddr, port))
 	nodeOptions = append(nodeOptions, libp2p.ListenAddrs(sourceMultiAddr))
-
 	// check if there is a host IP we can use to replace Docker's internal IP
 	hostIP, err := readHostIPFromFile(hostIPFile)
 	if err != nil || hostIP == "" {
@@ -87,7 +85,7 @@ func NewNode(ctx context.Context) (*P2PNode, error) {
 		return nil, err
 	}
 
-	// wrap the node with the routed host
+	// wrap the node with the routed host to improve network performance
 	rnode := routedhost.Wrap(node, p2pNode.dht)
 	p2pNode.Host = rnode
 	log.Debugf("Routed node created")
@@ -101,11 +99,26 @@ func NewNode(ctx context.Context) (*P2PNode, error) {
 		return nil, err
 	}
 
+	err = deleteNodeInfoFile()
+	if err != nil {
+		log.Errorf("error deleting node info file: %s", err)
+		return nil, err
+	}
+
+	// log the p2p node's ID
+	log.Infof("node created: %s", p2pNode.ID().Pretty())
+	saveNodeInfo("Node ID: " + p2pNode.ID().Pretty())
+
+	// log the p2p node's listening addresses
+	for _, addr := range p2pNode.Addrs() {
+		log.Infof("listening on: %s", addr.String())
+	}
+
 	return p2pNode, nil
 }
 
 // Initializes the DHT for the libp2p node in server mode.
-func (p *P2PNode) initializeDHT(opts ...dht.Option) error {
+func (p *P2PNode) initializeDHT(opts ...kadht.Option) error {
 	serverModeOpt := kadht.Mode(kadht.ModeServer)
 	opts = append(opts, serverModeOpt)
 	p.dht = &discovery.KadDHT{}