From 66385ce615451913f066199e3d174c618b3e243d Mon Sep 17 00:00:00 2001
From: Justin Langston <justin@bitpay.com>
Date: Wed, 26 Dec 2018 15:13:04 -0500
Subject: [PATCH] feat(service): support multiple sync nodes

failover p2p service support for clusters of bitcore nodes
---
 packages/bitcore-node/src/models/state.ts | 24 ++++++++++++++++++++
 packages/bitcore-node/src/services/p2p.ts | 27 +++++++++++++++++++----
 2 files changed, 47 insertions(+), 4 deletions(-)

diff --git a/packages/bitcore-node/src/models/state.ts b/packages/bitcore-node/src/models/state.ts
index cc0e44d3f11..a566dcf72f9 100644
--- a/packages/bitcore-node/src/models/state.ts
+++ b/packages/bitcore-node/src/models/state.ts
@@ -1,5 +1,6 @@
 import { BaseModel } from './base';
 import { ObjectID } from 'mongodb';
+import os from 'os';
 
 export type IState = {
   _id?: ObjectID;
@@ -13,6 +14,29 @@ export class State extends BaseModel<IState> {
   allowedPaging = [];
 
   onConnect() {}
+
+  async getSingletonState() {
+    return this.collection.findOneAndUpdate(
+      {},
+      { $setOnInsert: { created: new Date()}},
+      { upsert: true }
+    );
+  }
+
+  async getSyncingNode(params: { chain: string, network: string }): Promise<string> {
+    const { chain, network } = params;
+    const state = await this.getSingletonState();
+    return state.value![`syncingNode:${chain}:${network}`];
+  }
+
+  async selfNominateSyncingNode(params: { chain: string, network: string, lastHeartBeat: any }) {
+    const { chain, network, lastHeartBeat } = params;
+    const singleState = await this.getSingletonState();
+    this.collection.findOneAndUpdate(
+      { _id: singleState.value!._id, $or: [{ [`syncingNode:${chain}:${network}`]: { $exists: false } }, { [`syncingNode:${chain}:${network}`]: lastHeartBeat }]},
+      { $set: { [`syncingNode:${chain}:${network}`]: `${os.hostname}:${process.pid}:${Date.now()}` } }
+    );
+  }
 }
 
 export let StateModel = new State();
diff --git a/packages/bitcore-node/src/services/p2p.ts b/packages/bitcore-node/src/services/p2p.ts
index e4fc7e83257..a8ae021f229 100644
--- a/packages/bitcore-node/src/services/p2p.ts
+++ b/packages/bitcore-node/src/services/p2p.ts
@@ -7,6 +7,7 @@ import { TransactionModel } from '../models/transaction';
 import { Bitcoin } from '../types/namespaces/Bitcoin';
 import { StateModel } from '../models/state';
 import { SpentHeightIndicators } from '../types/Coin';
+import os from 'os';
 const Chain = require('../chain');
 const LRU = require('lru-cache');
 
@@ -22,6 +23,7 @@ export class P2pService {
   private pool: any;
   private invCache: any;
   private initialSyncComplete: boolean;
+  private isSyncingNode: boolean;
   constructor(params) {
     const { chain, network, chainConfig } = params;
     this.chain = chain;
@@ -32,6 +34,7 @@ export class P2pService {
     this.events = new EventEmitter();
     this.syncing = false;
     this.initialSyncComplete = false;
+    this.isSyncingNode = false;
     this.invCache = new LRU({ max: 10000 });
     this.messages = new this.bitcoreP2p.Messages({
       network: this.bitcoreLib.Networks.get(this.network)
@@ -76,7 +79,7 @@ export class P2pService {
         network: this.network,
         hash
       });
-      if (!this.invCache.get(hash)) {
+      if (this.isSyncingNode && !this.invCache.get(hash)) {
         this.processTransaction(message.transaction);
         this.events.emit('transaction', message.transaction);
       }
@@ -93,7 +96,7 @@ export class P2pService {
         hash
       });
 
-      if (!this.invCache.get(hash)) {
+      if (this.isSyncingNode && !this.invCache.get(hash)) {
         this.invCache.set(hash);
         this.events.emit(hash, message.block);
         this.events.emit('block', message.block);
@@ -112,7 +115,7 @@ export class P2pService {
     });
 
     this.pool.on('peerinv', (peer, message) => {
-      if (!this.syncing) {
+      if (this.isSyncingNode && !this.syncing) {
         const filtered = message.inventory.filter(inv => {
           const hash = this.bitcoreLib.encoding
             .BufferReader(inv.hash)
@@ -304,6 +307,22 @@ export class P2pService {
     logger.debug(`Started worker for chain ${this.chain}`);
     this.setupListeners();
     await this.connect();
-    this.sync();
+    setInterval(async () => {
+      const syncingNode = await StateModel.getSyncingNode({chain: this.chain, network: this.network});
+      const [hostname, pid] = syncingNode.split(':');
+      const amSyncingNode = (hostname === os.hostname() && pid === process.pid.toString());
+      if (amSyncingNode) {
+        StateModel.selfNominateSyncingNode({ chain: this.chain, network: this.network, lastHeartBeat: syncingNode });
+        if (!this.isSyncingNode) {
+          logger.info(`This worker is now the syncing node for ${this.chain} ${this.network}`);
+          this.isSyncingNode = true;
+          this.sync();
+        }
+      } else {
+        setTimeout(() => {
+          StateModel.selfNominateSyncingNode({ chain: this.chain, network: this.network, lastHeartBeat: syncingNode });
+        }, 5000)
+      }
+    }, 1000);
   }
 }