Added customizable quorum to FallbackProvider (#4160).

Author: ricmoo

src.ts/providers/default-provider.ts

@@ -11,6 +11,7 @@ import { QuickNodeProvider } from "./provider-quicknode.js";
 
 import { FallbackProvider } from "./provider-fallback.js";
 import { JsonRpcProvider } from "./provider-jsonrpc.js";
+import { Network } from "./network.js";
 import { WebSocketProvider } from "./provider-websocket.js";
 
 import type { AbstractProvider } from "./abstract-provider.js";
@@ -22,6 +23,8 @@ function isWebSocketLike(value: any): value is WebSocketLike {
         typeof(value.close) === "function");
 }
 
+const Testnets = "goerli kovan sepolia classicKotti optimism-goerli arbitrum-goerli matic-mumbai bnbt".split(" ");
+
 export function getDefaultProvider(network: string | Networkish | WebSocketLike, options?: any): AbstractProvider {
     if (options == null) { options = { }; }
 
@@ -33,6 +36,13 @@ export function getDefaultProvider(network: string | Networkish | WebSocketLike,
         return new WebSocketProvider(network);
     }
 
+    // Get the network name, if possible
+    let name: null | string = null;
+    try {
+        name = Network.from(network).name;
+    } catch (error) { }
+
+
     const providers: Array<AbstractProvider> = [ ];
 
     if (options.alchemy !== "-") {
@@ -96,7 +106,19 @@ export function getDefaultProvider(network: string | Networkish | WebSocketLike,
         operation: "getDefaultProvider"
     });
 
+    // No need for a FallbackProvider
     if (providers.length === 1) { return providers[0]; }
 
-    return new FallbackProvider(providers);
+    // We use the floor because public third-party providers can be unreliable,
+    // so a low number of providers with a large quorum will fail too often
+    let quorum = Math.floor(providers.length / 2);
+
+    // Testnets don't need as strong a security gaurantee and speed is
+    // more useful during testing
+    if (name && Testnets.indexOf(name) !== -1) { quorum = 1; }
+
+    // Provided override qorum takes priority
+    if (options && options.quorum) { quorum = options.quorum; }
+
+    return new FallbackProvider(providers, undefined, { quorum });
 }

src.ts/providers/provider-fallback.ts

@@ -165,16 +165,20 @@ async function waitForSync(config: Config, blockNumber: number): Promise<void> {
 export type FallbackProviderOptions = {
     // How many providers must agree on a value before reporting
     // back the response
-    quorum: number;
+    quorum?: number;
 
     // How many providers must have reported the same event
-    // for it to be emitted
-    eventQuorum: number;
+    // for it to be emitted (currently unimplmented)
+    eventQuorum?: number;
 
     // How many providers to dispatch each event to simultaneously.
     // Set this to 0 to use getLog polling, which implies eventQuorum
-    // is equal to quorum.
-    eventWorkers: number;
+    // is equal to quorum. (currently unimplemented)
+    eventWorkers?: number;
+
+    cacheTimeout?: number;
+
+    pollingInterval?: number;
 };
 
 type RunnerResult = { result: any } | { error: Error };
@@ -380,8 +384,9 @@ export class FallbackProvider extends AbstractProvider {
      *  If a [[Provider]] is included in %%providers%%, defaults are used
      *  for the configuration.
      */
-    constructor(providers: Array<AbstractProvider | FallbackProviderConfig>, network?: Networkish) {
-        super(network);
+    constructor(providers: Array<AbstractProvider | FallbackProviderConfig>, network?: Networkish, options?: FallbackProviderOptions) {
+        super(network, options);
+
         this.#configs = providers.map((p) => {
             if (p instanceof AbstractProvider) {
                 return Object.assign({ provider: p }, defaultConfig, defaultState );
@@ -393,7 +398,15 @@ export class FallbackProvider extends AbstractProvider {
         this.#height = -2;
         this.#initialSyncPromise = null;
 
-        this.quorum = 2; //Math.ceil(providers.length /  2);
+        if (options && options.quorum != null) {
+            this.quorum = options.quorum;
+        } else {
+            this.quorum = Math.ceil(this.#configs.reduce((accum, config) => {
+                accum += config.weight;
+                return accum;
+            }, 0) / 2);
+        }
+
         this.eventQuorum = 1;
         this.eventWorkers = 1;