ethereum: disallow http(s) RPC transports

fixes #776

Signed-off-by: Ben Burns <[email protected]>

packages/caliper-ethereum/lib/ethereum.js

@@ -38,13 +38,38 @@ class Ethereum extends BlockchainInterface {
      */
     constructor(workerIndex) {
         super();
-        let configPath = CaliperUtils.resolvePath(ConfigUtil.get(ConfigUtil.keys.NetworkConfig));
         this.bcType = 'ethereum';
-        this.ethereumConfig = require(configPath).ethereum;
+
+        let configPath = CaliperUtils.resolvePath(ConfigUtil.get(ConfigUtil.keys.NetworkConfig));
+        let ethereumConfig = require(configPath).ethereum;
+
+        // throws on configuration error
+        this.checkConfig(ethereumConfig);
+
+        this.ethereumConfig = ethereumConfig;
         this.web3 = new Web3(this.ethereumConfig.url);
         this.web3.transactionConfirmationBlocks = this.ethereumConfig.transactionConfirmationBlocks;
         this.clientIndex = workerIndex;
     }
+
+    checkConfig(ethereumConfig) {
+        if (!ethereumConfig.url) {
+            throw new Error(
+                "No URL given to access the Ethereum SUT. Please check your network configuration. " +
+                "Please see https://hyperledger.github.io/caliper/v0.3/ethereum-config/ for more info."
+            );
+        }
+
+        if (ethereumConfig.url.toLowerCase().indexOf("http") == 0) { 
+            throw new Error(
+                "Ethereum benchmarks must not use http(s) RPC connections, as there is no way to guarantee the " +
+                "order of submitted transactions when using other transports. For more information, please see " +
+                "https://github.com/hyperledger/caliper/issues/776#issuecomment-624771622"
+            );
+        }
+
+        //TODO: add validation logic for the rest of the configuration object
+    }
 
     /**
      * Retrieve the blockchain type the implementation relates to