Merge pull request #37 from EYBlockchain/westlad/wait-for-contract

fix: autostart waits for shield contract deployment

README.md

@@ -172,6 +172,8 @@ Send a `post` request to `http://localhost:9000/start` to start the merkle-tree'
 
 You can ask Timber to start automatically by setting the environment variable `AUTOSTART` to anything that is truthy.  This is useful when you are deploying another Timber instance to an already-running ZKP solution. In this case, Timber will take contract (name, address, treeId) from its config file. Depending on your configuration, not all of these may be needed.  Often Timber can infer the contract address from build artefacts.  
 
+If `AUTOSTART` is used, it will attempt to obtain a contract address and will try to do this `AUTOSTART_RETRIES` (default 20) times, every three seconds, before giving up.  This is useful if the contracts are not deployed before Timber is started.
+
 ##### Update the merkle-tree database:
 
 Send a `patch` request to `http://localhost:9000/update`. Given the leaves now stored in the mongodb, this `update` command will calculate all of the intermediate nodes from the leaves to the root, and store all of these nodes in the mongodb.

merkle-tree/src/auto-start.js

@@ -1,6 +1,7 @@
 import axios from 'axios';
 import config from 'config';
 import logger from './logger';
+import uw from './utils-web3';
 /**
 function to automatically start the Timber instance.  This is useful if you are
 starting it up in an already-established blockchain environment.
@@ -14,6 +15,27 @@ const autoStart = async () => {
       contractAddress: config.contracts[contractName].address,
       treeId: config.contracts[contractName].treeId,
     };
+    // if we haven't been given a contractAddress, it's best to make sure that
+    // Timber has the ability to infer one. Otherwise Timber will fall over. If
+    // the build artefacts don't exist yet then we need to wait.
+    // Stop eslint complaining because we DO want delays in this loop
+    let retries = process.env.AUTOSTART_RETRIES || 20;
+    while (!data.contractAddress) {
+      try {
+        // eslint-disable-next-line no-await-in-loop
+        data.contractAddress = await uw.getContractAddress(contractName);
+        // we want to catch if the above function throws OR returns undefined
+        if (data.contractAddress === undefined) throw new Error('undefined contract address');
+        logger.info(`Contract address for contract ${contractName} is ${data.contractAddress}`);
+      } catch (err) {
+        if (retries === 0) throw new Error(err);
+        retries--;
+        logger.warn('Unable to find a contract address. Retrying in 3 seconds.');
+        // eslint-disable-next-line no-await-in-loop
+        await new Promise(resolve => setTimeout(resolve, 3000));
+      }
+    }
+    // Now that we are fairly sure calling start will work, we can go ahead.
     try {
       logger.debug(
         `Calling /start for Timber, with contractName '${contractName}' and url localhost`,

merkle-tree/src/utils-web3.js

@@ -7,6 +7,7 @@
 // First we need to connect to a websocket provider.
 // Important Note: Subscribe method only works with a websocket provider!
 
+import fs from 'fs';
 import Web3 from './web3';
 import logger from './logger';
 
@@ -67,8 +68,8 @@ let events = {};
 function getContractInterface(contractName) {
   logger.debug(`./src/utils-web3 getContractInterface(${contractName})`);
 
-  const path = `../build/contracts/${contractName}.json`;
-  const contractInterface = require(path); // eslint-disable-line global-require, import/no-dynamic-require
+  const path = `./build/contracts/${contractName}.json`;
+  const contractInterface = JSON.parse(fs.readFileSync(path));
   logger.silly(`contractInterface: ${JSON.stringify(contractInterface, null, 2)}`);
   return contractInterface;
 }

merkle-tree/src/web3.js

@@ -26,9 +26,9 @@ export default {
       config.web3.options,
     );
 
-    provider.on('error', console.error);
+    provider.on('error', err => logger.error(err));
     provider.on('connect', () => logger.info('Blockchain Connected ...'));
-    provider.on('end', console.error);
+    provider.on('end', () => logger.error('Blockchain Disconnected'));
 
     this.web3 = new Web3(provider);