More robust FallbackProvider broadcast (#4186, #4297, #4442).

Author: ricmoo

src.ts/_tests/test-providers-fallback.ts

@@ -0,0 +1,95 @@
+import assert from "assert";
+
+import {
+    isError, makeError,
+
+    AbstractProvider, FallbackProvider, Network,
+} from "../index.js";
+
+import type {
+    PerformActionRequest
+} from "../index.js";
+
+
+
+const network = Network.from("mainnet");
+
+function stall(duration: number): Promise<void> {
+    return  new Promise((resolve) => { setTimeout(resolve, duration); });
+}
+
+
+export type Performer = (req: PerformActionRequest) => Promise<any>;
+
+export class MockProvider extends AbstractProvider {
+    readonly _perform: Performer;
+
+    constructor(perform: Performer) {
+        super(network, { cacheTimeout: -1 });
+        this._perform = perform;
+    }
+
+    async _detectNetwork(): Promise<Network> { return network; }
+
+    async perform(req: PerformActionRequest): Promise<any> {
+        return await this._perform(req);
+    }
+}
+
+describe("Test Fallback broadcast", function() {
+
+    const txHash = "0x33017397ef7c7943dee3b422aec52b0a210de58d73d49c1b3ce455970f01c83a";
+
+    async function test(actions: Array<{ timeout: number, error?: Error }>): Promise<any> {
+        // https://sepolia.etherscan.io/tx/0x33017397ef7c7943dee3b422aec52b0a210de58d73d49c1b3ce455970f01c83a
+        const tx = "0x02f87683aa36a7048459682f00845d899ef982520894b5bdaa442bb34f27e793861c456cd5bdc527ac8c89056bc75e2d6310000080c001a07503893743e94445b2361a444343757e6f59d52e19e9b3f65eb138d802eaa972a06e4e9bc10ff55474f9aac0a4c284733b4195cb7b273de5e7465ce75a168e0c38";
+
+        const providers: Array<MockProvider> = actions.map(({ timeout, error }) => {
+            return new MockProvider(async (r) => {
+                if (r.method === "getBlockNumber") { return 1; }
+                if (r.method === "broadcastTransaction") {
+                    await stall(timeout);
+                    if (error) { throw error; }
+                    return txHash;
+                }
+                throw new Error(`unhandled method: ${ r.method }`);
+            });
+        });;
+
+        const provider = new FallbackProvider(providers);
+        return await provider.broadcastTransaction(tx);
+    }
+
+    it("picks late non-failed broadcasts", async function() {
+        const result = await test([
+            { timeout: 200, error: makeError("already seen", "UNKNOWN_ERROR") },
+            { timeout: 4000, error: makeError("already seen", "UNKNOWN_ERROR") },
+            { timeout: 400 },
+        ]);
+        assert(result.hash === txHash, "result.hash === txHash");
+    });
+
+    it("picks late non-failed broadcasts with quorum-met red-herrings", async function() {
+        const result = await test([
+            { timeout: 200, error: makeError("bad nonce", "NONCE_EXPIRED") },
+            { timeout: 400, error: makeError("bad nonce", "NONCE_EXPIRED") },
+            { timeout: 1000 },
+        ]);
+        assert(result.hash === txHash, "result.hash === txHash");
+    });
+
+    it("insufficient funds short-circuit broadcast", async function() {
+        await assert.rejects(async function() {
+            const result = await test([
+                { timeout: 200, error: makeError("is broke", "INSUFFICIENT_FUNDS") },
+                { timeout: 400, error: makeError("is broke", "INSUFFICIENT_FUNDS") },
+                { timeout: 800 },
+                { timeout: 1000 },
+            ]);
+            console.log(result);
+        }, function(error: unknown) {
+            assert(isError(error, "INSUFFICIENT_FUNDS"));
+            return true;
+        });
+    });
+});

src.ts/providers/provider-fallback.ts

@@ -5,7 +5,7 @@
  *  @_section: api/providers/fallback-provider:Fallback Provider [about-fallback-provider]
  */
 import {
-    getBigInt, getNumber, assert, assertArgument
+    assert, assertArgument, getBigInt, getNumber, isError
 } from "../utils/index.js";
 
 import { AbstractProvider } from "./abstract-provider.js";
@@ -707,16 +707,46 @@ export class FallbackProvider extends AbstractProvider {
         // a cost on the user, so spamming is safe-ish. Just send it to
         // every backend.
         if (req.method === "broadcastTransaction") {
-            const results = await Promise.all(this.#configs.map(async ({ provider, weight }) => {
+            // Once any broadcast provides a positive result, use it. No
+            // need to wait for anyone else
+            const results: Array<null | TallyResult> = this.#configs.map((c) => null);
+            const broadcasts = this.#configs.map(async ({ provider, weight }, index) => {
                 try {
                     const result = await provider._perform(req);
-                    return Object.assign(normalizeResult({ result }), { weight });
+                    results[index] = Object.assign(normalizeResult({ result }), { weight });
                 } catch (error: any) {
-                    return Object.assign(normalizeResult({ error }), { weight });
+                    results[index] = Object.assign(normalizeResult({ error }), { weight });
                 }
-            }));
+            });
+
+            // As each promise finishes...
+            while (true) {
+                // Check for a valid broadcast result
+                const done = <Array<any>>results.filter((r) => (r != null));
+                for (const { value } of done) {
+                    if (!(value instanceof Error)) { return value; }
+                }
+
+                // Check for a legit broadcast error (one which we cannot
+                // recover from; some nodes may return the following red
+                // herring events:
+                // - alredy seend (UNKNOWN_ERROR)
+                // - NONCE_EXPIRED
+                // - REPLACEMENT_UNDERPRICED
+                const result = checkQuorum(this.quorum, <Array<any>>results.filter((r) => (r != null)));
+                if (isError(result, "INSUFFICIENT_FUNDS")) {
+                    throw result;
+                }
+
+                // Kick off the next provider (if any)
+                const waiting = broadcasts.filter((b, i) => (results[i] == null));
+                if (waiting.length === 0) { break; }
+                await Promise.race(waiting);
+            }
 
-            const result = getAnyResult(this.quorum, results);
+            // Use standard quorum results; any result was returned above,
+            // so this will find any error that met quorum if any
+            const result = getAnyResult(this.quorum, <Array<any>>results);
             assert(result !== undefined, "problem multi-broadcasting", "SERVER_ERROR", {
                 request: "%sub-requests",
                 info: { request: req, results: results.map(stringify) }