persistence for the blockchain + everything through the chain instead of broadcasting

app/index.js

@@ -38,7 +38,6 @@ const QueryEngine = require('@comunica/query-sparql').QueryEngine;
 
 const N3              = require('n3');
 const jsonld          = require('jsonld');
-const DataFactory     = require('n3').DataFactory;
 var   mqtt            = require('mqtt');
 var   aedes           = require('aedes')(); /* aedes is a stream-based MQTT broker */
 var   MQTTserver      = require('net').createServer(aedes.handle);
@@ -54,11 +53,10 @@ const app = express();
 const bc = new Blockchain();
 const wallet = new Wallet();
 const tp = new TransactionPool();
-const p2pServer = new P2pServer(bc, tp);
+const p2pServer = new P2pServer(bc, tp,'./persist_block_chain.json');
 const miner = new Miner(bc, tp, wallet, p2pServer);
 
 const parser        = new N3.Parser(); //({format: 'application/n-quads'});
-const store         = new N3.Store();
 const myEngine = new QueryEngine();
 
 app.use(bodyParser.json());
@@ -167,31 +165,15 @@ app.get('/IoTdeviceRegistration', (req, res)=> {
     } 
 //let SenShaMartOnt = SSNmetadata;
 //SenShaMartOnt.push(SenSHaMArtExt); */
-console.log(SenShaMartDesc)
-jsonld.toRDF(SenShaMartDesc, {format: 'application/n-quads'}, 
-  (err, nquads) => {
-    console.log(nquads)
-    var metaDataTransaction = wallet.createMetadata( 
-      nquads, tp);
-
-   parser.parse(
-    nquads,
-       (error, quadN, prefixes) => {
-      if (quadN){
-      store.addQuad(DataFactory.quad(
-        DataFactory.namedNode(quadN.subject.id), 
-        DataFactory.namedNode(quadN.predicate.id), 
-        DataFactory.namedNode(quadN.object.id)));
-      }  
-      else {
-        console.log("# That's all, folks!", prefixes);
-      } 
-       });
- //console.log(metaDataTransaction.SSNmetadata)
- p2pServer.broadcastMetadata(metaDataTransaction);
-});
-});
- res.json("MetadataTransactionCreated");
+  console.log(SenShaMartDesc)
+  jsonld.toRDF(SenShaMartDesc, {format: 'application/n-quads'}, 
+    (err, nquads) => {
+      console.log(nquads)
+      var metaDataTransaction = wallet.createMetadata( 
+        nquads, tp);
+    });
+  });
+  res.json("MetadataTransactionCreated");
 });
 
 //////////////////////////////////////////////////
@@ -200,7 +182,7 @@ app.post('/mine', (req, res) => {
   const block = bc.addBlock(req.body.data);
   console.log(`New block added: ${block.toString()}`);
 
-  p2pServer.syncChains();
+  p2pServer.newBlock(block);
 
   res.redirect('/blocks');
 });
@@ -208,7 +190,7 @@ app.post('/mine', (req, res) => {
 app.post('/PaymentTransaction', (req, res) => {
   const { recipient, amount } = req.body;
   const transaction = wallet.createTransaction(recipient, amount, bc, tp);
-  p2pServer.broadcastTransaction(transaction);
+  //p2pServer.broadcastTransaction(transaction);
   res.redirect('/transactions');
 }); 
 
@@ -249,13 +231,14 @@ app.post("/UploadMetafile", upload.single('file'), (req, res) => {
 
 /////////////////////
 //Start of comunica sparql query code
-  app.post('/sparql', (req, res) => {
+app.post('/sparql', (req, res) => {
+  console.log(req.body);
   const {Select,subject,predicate,object,Limit}= req.body;
     const start = async function (a,b){  
       const bindingsStream = await myEngine.queryBindings(`SELECT ${Select} WHERE 
             {${subject} ${predicate} ${object}} LIMIT 
             ${Limit}`, { sources: [{ type: 'rdfjsSource', 
-            value: store}]
+            value: p2pServer.store}]
             });
       bindingsStream.on('data', (binding) => {
         console.log(binding.toString());

app/miner.js

@@ -25,9 +25,8 @@ class Miner {
     console.log(validTransactions);
    // const validMetadataS    = this.transactionPool.metadataS;
     const block = this.blockchain.addBlock([validTransactions, validMetadataS]);
-    this.p2pServer.syncChains();
+    this.p2pServer.newBlock(block);
     this.transactionPool.clear();
-    this.p2pServer.broadcastClearTransactions();
  
     return block;
   }

app/p2p-server.js

@@ -1,4 +1,9 @@
 const Websocket = require('ws');
+const N3 = require('n3');
+const parser = new N3.Parser(); //({format: 'application/n-quads'});
+const DataFactory = require('n3').DataFactory;
+const fs = require('fs');
+const process = require('process');
 
 const P2P_PORT = process.env.P2P_PORT || 5000;
 const peers = process.env.PEERS ? process.env.PEERS.split(',') : [];
@@ -10,10 +15,21 @@ const MESSAGE_TYPES = {
 };
 
 class P2pServer {
-  constructor(blockchain, transactionPool) {
+  constructor(blockchain, transactionPool,chainStorageLocation) {
     this.blockchain = blockchain;
     this.transactionPool = transactionPool;
     this.sockets = [];
+    this.store = new N3.Store();
+    this.chainStorageLocation = chainStorageLocation;
+
+    //possible race if deleted after check, but we live with it I guess
+    if (fs.existsSync(this.chainStorageLocation)) {
+      const rawPersistedChain = fs.readFileSync(this.chainStorageLocation, 'utf8');
+      const chain = JSON.parse(rawPersistedChain);
+      this.newChain(chain, false);
+    } else {
+      console.log("Didn't find a persisted chain, starting from genesis");
+    }
   }
 
   listen() {
@@ -47,7 +63,7 @@ class P2pServer {
       const data = JSON.parse(message);
       switch(data.type) {
         case MESSAGE_TYPES.chain:
-          this.blockchain.replaceChain(data.chain);
+          newChain(data.chain);
           break;
         case MESSAGE_TYPES.transaction:
           this.transactionPool.updateOrAddTransaction(data.transaction);
@@ -62,6 +78,67 @@ class P2pServer {
     });
   }
 
+  newBlock(block) {
+    this.onNewBlock(block.data);
+    this.syncChains();
+    this.persistChain(this.blockchain.chain);
+  }
+
+  newChain(chain,persist) {
+    if (!this.blockchain.replaceChain(chain)) {
+      //failed to replace
+      return;
+    }
+    if (typeof persist === "undefined" || persist) {
+      this.persistChain(chain);
+    }
+    //dirty clear
+    this.store = new N3.Store();
+    for (var block in this.blockchain.chain) {
+      this.onNewBlock(block);
+    }
+  }
+
+  persistChain(chain) {
+    try {
+      fs.writeFileSync(
+        this.chainStorageLocation,
+        JSON.stringify(chain));
+    } catch (err) {
+      console.error("Couldn't persist chain, aborting");
+      process.exit(-1);
+    }
+  }
+
+  onNewBlock(block) {
+    //block data is of form [transactions,metadatas]
+    if (block.length != 2) {
+      //assert?
+      return;
+    }
+    const metadatas = block[1];
+
+    for (var metadata in metadatas) {
+      if (!(SSNmetadata in metadata)) {
+        //assert?
+        return;
+      }
+
+      var ssn = metadata.SSNmetadata;
+
+      parser.parse(
+        ssn,
+        (error, quadN, prefixes) => {
+          if (quadN) {
+            store.addQuad(DataFactory.quad(
+              DataFactory.namedNode(quadN.subject.id),
+              DataFactory.namedNode(quadN.predicate.id),
+              DataFactory.namedNode(quadN.object.id)));
+          }
+        });
+    }
+  }
+
   sendChain(socket) {
     socket.send(JSON.stringify({
       type: MESSAGE_TYPES.chain,
@@ -69,36 +146,36 @@ class P2pServer {
     }));
   }
 
-  sendTransaction(socket, transaction) {
-    socket.send(JSON.stringify({
-      type: MESSAGE_TYPES.transaction,
-      transaction
-    }));
-  }
+  //sendTransaction(socket, transaction) {
+  //  socket.send(JSON.stringify({
+  //    type: MESSAGE_TYPES.transaction,
+  //    transaction
+  //  }));
+  //}
   
-  sendMetadata(socket, metadata) {
-    socket.send(JSON.stringify({ 
-      type: MESSAGE_TYPES.metadata,
-      metadata
-    }));
-  }
+  //sendMetadata(socket, metadata) {
+  //  socket.send(JSON.stringify({ 
+  //    type: MESSAGE_TYPES.metadata,
+  //    metadata
+  //  }));
+  //}
   syncChains() {
     this.sockets.forEach(socket => this.sendChain(socket));
   }
 
-  broadcastTransaction(transaction) {
-    this.sockets.forEach(socket => this.sendTransaction(socket, transaction));
-  }
+  //broadcastTransaction(transaction) {
+  //  this.sockets.forEach(socket => this.sendTransaction(socket, transaction));
+  //}
 
-  broadcastMetadata(metadata) {
-    this.sockets.forEach(socket => this.sendMetadata(socket, metadata));
-  }
+  //broadcastMetadata(metadata) {
+  //  this.sockets.forEach(socket => this.sendMetadata(socket, metadata));
+  //}
 
-  broadcastClearTransactions() {
-    this.sockets.forEach(socket => socket.send(JSON.stringify({
-      type: MESSAGE_TYPES.clear_transactions
-    })));
-  }
+  //broadcastClearTransactions() {
+  //  this.sockets.forEach(socket => socket.send(JSON.stringify({
+  //    type: MESSAGE_TYPES.clear_transactions
+  //  })));
+  //}
 }
 
 module.exports = P2pServer;

blockchain/block.js

@@ -24,7 +24,12 @@ class Block {
   static genesis() {
     return new this('Genesis time', '-----', 'f1r57-h45h', [], 0, DIFFICULTY);
   }
+  //we want this to eventually be continously running where there are things in the pool,
+  //however as node is single threaded, this almost has to be a fiber, and yield after every
+  //other iteration to allow for meaningful forward progress
 
+  //we can either add all new transactions into the block as we see them, or stay with the starting list, idk which
+  //to be done later
   static mineBlock(lastBlock, data) {
     let hash, timestamp;
     const lastHash = lastBlock.hash;

blockchain/index.js

@@ -28,17 +28,19 @@ class Blockchain {
     return true;
   }
 
+  //return false on failure, true on success
   replaceChain(newChain) {
     if (newChain.length <= this.chain.length) {
       console.log('Received chain is not longer than the current chain.');
-      return;
+      return false;
     } else if (!this.isValidChain(newChain)) {
       console.log('The received chain is not valid.');
-      return;
+      return false;
     }
 
     console.log('Replacing blockchain with the new chain.');
     this.chain = newChain;
+    return true;
   }
 }