1 files changed, 41 insertions, 0 deletions
diff --git a/packages/website/ts/subproviders/redundant_rpc_subprovider.ts b/packages/website/ts/subproviders/redundant_rpc_subprovider.ts
new file mode 100644
index 000000000..a6c53ebd1
--- /dev/null
+++ b/packages/website/ts/subproviders/redundant_rpc_subprovider.ts
@@ -0,0 +1,41 @@
+import * as _ from 'lodash';
+import {JSONRPCPayload} from 'ts/types';
+import promisify = require('es6-promisify');
+import Subprovider = require('web3-provider-engine/subproviders/subprovider');
+import RpcSubprovider = require('web3-provider-engine/subproviders/rpc');
+
+export class RedundantRPCSubprovider extends Subprovider {
+    private rpcs: RpcSubprovider[];
+    constructor(endpoints: string[]) {
+        super();
+        this.rpcs = _.map(endpoints, endpoint => {
+            return new RpcSubprovider({
+                rpcUrl: endpoint,
+            });
+        });
+    }
+    public async handleRequest(payload: JSONRPCPayload, next: () => void,
+                               end: (err?: Error, data?: any) =>  void): Promise<void> {
+        const rpcsCopy = this.rpcs.slice();
+        try {
+            const data = await this.firstSuccessAsync(rpcsCopy, payload, next);
+            end(null, data);
+        } catch (err) {
+            end(err);
+        }
+
+    }
+    private async firstSuccessAsync(rpcs: RpcSubprovider[], payload: JSONRPCPayload, next: () => void): Promise<any> {
+        let lastErr;
+        for (const rpc of rpcs) {
+            try {
+                const data = await promisify(rpc.handleRequest.bind(rpc))(payload, next);
+                return data;
+            } catch (err) {
+                lastErr = err;
+                continue;
+            }
+        }
+        throw Error(lastErr);
+    }
+}