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18x 18x 18x 18x 18x 18x 18x 22x 1x 1x 17x 17x 17x 22x 15x 15x 2x 2x 2x 2x 2x 2x 2x 2x 2x 137x 137x 137x 137x 137x 137x 144x 272x 272x 272x 272x 272x 137x 137x 122x 122x 122x 144x 258x 13x 13x 258x 122x 122x 122x 42x 42x 286x 858x 858x 286x 286x 42x | /**
* A **FallbackProvider** provides resilience, security and performance
* in a way that is customizable and configurable.
*
* @_section: api/providers/fallback-provider:Fallback Provider [about-fallback-provider]
*/
import {
assert, assertArgument, getBigInt, getNumber, isError
} from "../utils/index.js";
import { AbstractProvider } from "./abstract-provider.js";
import { Network } from "./network.js"
import type { PerformActionRequest } from "./abstract-provider.js";
import type { Networkish } from "./network.js"
const BN_1 = BigInt("1");
const BN_2 = BigInt("2");
function shuffle<T = any>(array: Array<T>): void {
for (let i = array.length - 1; i > 0; i--) {
const j = Math.floor(Math.random() * (i + 1));
const tmp = array[i];
array[i] = array[j];
array[j] = tmp;
}
}
function stall(duration: number): Promise<void> {
return new Promise((resolve) => { setTimeout(resolve, duration); });
}
function getTime(): number { return (new Date()).getTime(); }
function stringify(value: any): string {
return JSON.stringify(value, (key, value) => {
if (typeof(value) === "bigint") {
return { type: "bigint", value: value.toString() };
}
return value;
});
}
/**
* A configuration entry for how to use a [[Provider]].
*/
export interface FallbackProviderConfig {
/**
* The provider.
*/
provider: AbstractProvider;
/**
* The amount of time to wait before kicking off the next provider.
*
* Any providers that have not responded can still respond and be
* counted, but this ensures new providers start.
*/
stallTimeout?: number;
/**
* The priority. Lower priority providers are dispatched first.
*/
priority?: number;
/**
* The amount of weight a provider is given against the quorum.
*/
weight?: number;
};
const defaultConfig = { stallTimeout: 400, priority: 1, weight: 1 };
// We track a bunch of extra stuff that might help debug problems or
// optimize infrastructure later on.
/**
* The statistics and state maintained for a [[Provider]].
*/
export interface FallbackProviderState extends Required<FallbackProviderConfig> {
/**
* The most recent blockNumber this provider has reported (-2 if none).
*/
blockNumber: number;
/**
* The number of total requests ever sent to this provider.
*/
requests: number;
/**
* The number of responses that errored.
*/
errorResponses: number;
/**
* The number of responses that occured after the result resolved.
*/
lateResponses: number;
/**
* How many times syncing was required to catch up the expected block.
*/
outOfSync: number;
/**
* The number of requests which reported unsupported operation.
*/
unsupportedEvents: number;
/**
* A rolling average (5% current duration) for response time.
*/
rollingDuration: number;
/**
* The ratio of quorum-agreed results to total.
*/
score: number;
}
interface Config extends FallbackProviderState {
_updateNumber: null | Promise<any>;
_network: null | Network;
_totalTime: number;
_lastFatalError: null | Error;
_lastFatalErrorTimestamp: number;
}
const defaultState = {
blockNumber: -2, requests: 0, lateResponses: 0, errorResponses: 0,
outOfSync: -1, unsupportedEvents: 0, rollingDuration: 0, score: 0,
_network: null, _updateNumber: null, _totalTime: 0,
_lastFatalError: null, _lastFatalErrorTimestamp: 0
};
async function waitForSync(config: Config, blockNumber: number): Promise<void> {
while (config.blockNumber < 0 || config.blockNumber < blockNumber) {
if (!config._updateNumber) {
config._updateNumber = (async () => {
try {
const blockNumber = await config.provider.getBlockNumber();
if (blockNumber > config.blockNumber) {
config.blockNumber = blockNumber;
}
} catch (error: any) {
config.blockNumber = -2;
config._lastFatalError = error;
config._lastFatalErrorTimestamp = getTime();
}
config._updateNumber = null;
})();
}
await config._updateNumber;
config.outOfSync++;
if (config._lastFatalError) { break; }
}
}
/**
* Additional options to configure a [[FallbackProvider]].
*/
export type FallbackProviderOptions = {
// How many providers must agree on a value before reporting
// back the response
quorum?: number;
// How many providers must have reported the same event
// 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. (currently unimplemented)
eventWorkers?: number;
cacheTimeout?: number;
pollingInterval?: number;
};
type RunnerResult = { result: any } | { error: Error };
type RunnerState = {
config: Config;
staller: null | Promise<void>;
didBump: boolean;
perform: null | Promise<any>;
result: null | RunnerResult;
}
function _normalize(value: any): string {
if (value == null) { return "null"; }
if (Array.isArray(value)) {
return "[" + (value.map(_normalize)).join(",") + "]";
}
if (typeof(value) === "object" && typeof(value.toJSON) === "function") {
return _normalize(value.toJSON());
}
switch (typeof(value)) {
case "boolean": case "symbol":
return value.toString();
case "bigint": case "number":
return BigInt(value).toString();
case "string":
return JSON.stringify(value);
case "object": {
const keys = Object.keys(value);
keys.sort();
return "{" + keys.map((k) => `${ JSON.stringify(k) }:${ _normalize(value[k]) }`).join(",") + "}";
}
}
console.log("Could not serialize", value);
throw new Error("Hmm...");
}
function normalizeResult(method: string, value: RunnerResult): { tag: string, value: any } {
if ("error" in value) {
const error = value.error;
let tag: string;
if (isError(error, "CALL_EXCEPTION")) {
tag = _normalize(Object.assign({ }, error, {
shortMessage: undefined, reason: undefined, info: undefined
}));
} else {
tag = _normalize(error)
}
return { tag, value: error };
}
const result = value.result;
return { tag: _normalize(result), value: result };
}
type TallyResult = {
tag: string;
value: any;
weight: number;
};
// This strategy picks the highest weight result, as long as the weight is
// equal to or greater than quorum
function checkQuorum(quorum: number, results: Array<TallyResult>): any | Error {
const tally: Map<string, { value: any, weight: number }> = new Map();
for (const { value, tag, weight } of results) {
const t = tally.get(tag) || { value, weight: 0 };
t.weight += weight;
tally.set(tag, t);
}
let best: null | { value: any, weight: number } = null;
for (const r of tally.values()) {
if (r.weight >= quorum && (!best || r.weight > best.weight)) {
best = r;
}
}
if (best) { return best.value; }
return undefined;
}
function getMedian(quorum: number, results: Array<TallyResult>): undefined | bigint | Error {
let resultWeight = 0;
const errorMap: Map<string, { weight: number, value: Error }> = new Map();
let bestError: null | { weight: number, value: Error } = null;
const values: Array<bigint> = [ ];
for (const { value, tag, weight } of results) {
if (value instanceof Error) {
const e = errorMap.get(tag) || { value, weight: 0 };
e.weight += weight;
errorMap.set(tag, e);
if (bestError == null || e.weight > bestError.weight) { bestError = e; }
} else {
values.push(BigInt(value));
resultWeight += weight;
}
}
if (resultWeight < quorum) {
// We have quorum for an error
if (bestError && bestError.weight >= quorum) { return bestError.value; }
// We do not have quorum for a result
return undefined;
}
// Get the sorted values
values.sort((a, b) => ((a < b) ? -1: (b > a) ? 1: 0));
const mid = Math.floor(values.length / 2);
// Odd-length; take the middle value
if (values.length % 2) { return values[mid]; }
// Even length; take the ceiling of the mean of the center two values
return (values[mid - 1] + values[mid] + BN_1) / BN_2;
}
function getAnyResult(quorum: number, results: Array<TallyResult>): undefined | any | Error {
// If any value or error meets quorum, that is our preferred result
const result = checkQuorum(quorum, results);
if (result !== undefined) { return result; }
// Otherwise, do we have any result?
for (const r of results) {
if (r.value) { return r.value; }
}
// Nope!
return undefined;
}
function getFuzzyMode(quorum: number, results: Array<TallyResult>): undefined | number {
if (quorum === 1) { return getNumber(<bigint>getMedian(quorum, results), "%internal"); }
const tally: Map<number, { result: number, weight: number }> = new Map();
const add = (result: number, weight: number) => {
const t = tally.get(result) || { result, weight: 0 };
t.weight += weight;
tally.set(result, t);
};
for (const { weight, value } of results) {
const r = getNumber(value);
add(r - 1, weight);
add(r, weight);
add(r + 1, weight);
}
let bestWeight = 0;
let bestResult: undefined | number = undefined;
for (const { weight, result } of tally.values()) {
// Use this result, if this result meets quorum and has either:
// - a better weight
// - or equal weight, but the result is larger
if (weight >= quorum && (weight > bestWeight || (bestResult != null && weight === bestWeight && result > bestResult))) {
bestWeight = weight;
bestResult = result;
}
}
return bestResult;
}
/**
* A **FallbackProvider** manages several [[Providers]] providing
* resilience by switching between slow or misbehaving nodes, security
* by requiring multiple backends to aggree and performance by allowing
* faster backends to respond earlier.
*
*/
export class FallbackProvider extends AbstractProvider {
/**
* The number of backends that must agree on a value before it is
* accpeted.
*/
readonly quorum: number;
/**
* @_ignore:
*/
readonly eventQuorum: number;
/**
* @_ignore:
*/
readonly eventWorkers: number;
readonly #configs: Array<Config>;
#height: number;
#initialSyncPromise: null | Promise<void>;
/**
* Creates a new **FallbackProvider** with %%providers%% connected to
* %%network%%.
*
* If a [[Provider]] is included in %%providers%%, defaults are used
* for the configuration.
*/
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 );
} else {
return Object.assign({ }, defaultConfig, p, defaultState );
}
});
this.#height = -2;
this.#initialSyncPromise = null;
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;
assertArgument(this.quorum <= this.#configs.reduce((a, c) => (a + c.weight), 0),
"quorum exceed provider weight", "quorum", this.quorum);
}
get providerConfigs(): Array<FallbackProviderState> {
return this.#configs.map((c) => {
const result: any = Object.assign({ }, c);
for (const key in result) {
if (key[0] === "_") { delete result[key]; }
}
return result;
});
}
async _detectNetwork(): Promise<Network> {
return Network.from(getBigInt(await this._perform({ method: "chainId" })));
}
// @TODO: Add support to select providers to be the event subscriber
//_getSubscriber(sub: Subscription): Subscriber {
// throw new Error("@TODO");
//}
/**
* Transforms a %%req%% into the correct method call on %%provider%%.
*/
async _translatePerform(provider: AbstractProvider, req: PerformActionRequest): Promise<any> {
switch (req.method) {
case "broadcastTransaction":
return await provider.broadcastTransaction(req.signedTransaction);
case "call":
return await provider.call(Object.assign({ }, req.transaction, { blockTag: req.blockTag }));
case "chainId":
return (await provider.getNetwork()).chainId;
case "estimateGas":
return await provider.estimateGas(req.transaction);
case "getBalance":
return await provider.getBalance(req.address, req.blockTag);
case "getBlock": {
const block = ("blockHash" in req) ? req.blockHash: req.blockTag;
return await provider.getBlock(block, req.includeTransactions);
}
case "getBlockNumber":
return await provider.getBlockNumber();
case "getCode":
return await provider.getCode(req.address, req.blockTag);
case "getGasPrice":
return (await provider.getFeeData()).gasPrice;
case "getPriorityFee":
return (await provider.getFeeData()).maxPriorityFeePerGas;
case "getLogs":
return await provider.getLogs(req.filter);
case "getStorage":
return await provider.getStorage(req.address, req.position, req.blockTag);
case "getTransaction":
return await provider.getTransaction(req.hash);
case "getTransactionCount":
return await provider.getTransactionCount(req.address, req.blockTag);
case "getTransactionReceipt":
return await provider.getTransactionReceipt(req.hash);
case "getTransactionResult":
return await provider.getTransactionResult(req.hash);
}
}
// Grab the next (random) config that is not already part of
// the running set
#getNextConfig(running: Set<RunnerState>): null | Config {
// @TODO: Maybe do a check here to favour (heavily) providers that
// do not require waitForSync and disfavour providers that
// seem down-ish or are behaving slowly
const configs = Array.from(running).map((r) => r.config)
// Shuffle the states, sorted by priority
const allConfigs = this.#configs.slice();
shuffle(allConfigs);
allConfigs.sort((a, b) => (a.priority - b.priority));
for (const config of allConfigs) {
if (config._lastFatalError) { continue; }
if (configs.indexOf(config) === -1) { return config; }
}
return null;
}
// Adds a new runner (if available) to running.
#addRunner(running: Set<RunnerState>, req: PerformActionRequest): null | RunnerState {
const config = this.#getNextConfig(running);
// No runners available
if (config == null) { return null; }
// Create a new runner
const runner: RunnerState = {
config, result: null, didBump: false,
perform: null, staller: null
};
const now = getTime();
// Start performing this operation
runner.perform = (async () => {
try {
config.requests++;
const result = await this._translatePerform(config.provider, req);
runner.result = { result };
} catch (error: any) {
config.errorResponses++;
runner.result = { error };
}
const dt = (getTime() - now);
config._totalTime += dt;
config.rollingDuration = 0.95 * config.rollingDuration + 0.05 * dt;
runner.perform = null;
})();
// Start a staller; when this times out, it's time to force
// kicking off another runner because we are taking too long
runner.staller = (async () => {
await stall(config.stallTimeout);
runner.staller = null;
})();
running.add(runner);
return runner;
}
// Initializes the blockNumber and network for each runner and
// blocks until initialized
async #initialSync(): Promise<void> {
let initialSync = this.#initialSyncPromise;
if (!initialSync) {
const promises: Array<Promise<any>> = [ ];
this.#configs.forEach((config) => {
promises.push((async () => {
await waitForSync(config, 0);
if (!config._lastFatalError) {
config._network = await config.provider.getNetwork();
}
})());
});
this.#initialSyncPromise = initialSync = (async () => {
// Wait for all providers to have a block number and network
await Promise.all(promises);
// Check all the networks match
let chainId: null | bigint = null;
for (const config of this.#configs) {
if (config._lastFatalError) { continue; }
const network = <Network>(config._network);
if (chainId == null) {
chainId = network.chainId;
} else if (network.chainId !== chainId) {
assert(false, "cannot mix providers on different networks", "UNSUPPORTED_OPERATION", {
operation: "new FallbackProvider"
});
}
}
})();
}
await initialSync
}
async #checkQuorum(running: Set<RunnerState>, req: PerformActionRequest): Promise<any> {
// Get all the result objects
const results: Array<TallyResult> = [ ];
for (const runner of running) {
if (runner.result != null) {
const { tag, value } = normalizeResult(req.method, runner.result);
results.push({ tag, value, weight: runner.config.weight });
}
}
// Are there enough results to event meet quorum?
if (results.reduce((a, r) => (a + r.weight), 0) < this.quorum) {
return undefined;
}
switch (req.method) {
case "getBlockNumber": {
// We need to get the bootstrap block height
if (this.#height === -2) {
this.#height = Math.ceil(getNumber(<bigint>getMedian(this.quorum, this.#configs.filter((c) => (!c._lastFatalError)).map((c) => ({
value: c.blockNumber,
tag: getNumber(c.blockNumber).toString(),
weight: c.weight
})))));
}
// Find the mode across all the providers, allowing for
// a little drift between block heights
const mode = getFuzzyMode(this.quorum, results);
if (mode === undefined) { return undefined; }
if (mode > this.#height) { this.#height = mode; }
return this.#height;
}
case "getGasPrice":
case "getPriorityFee":
case "estimateGas":
return getMedian(this.quorum, results);
case "getBlock":
// Pending blocks are in the mempool and already
// quite untrustworthy; just grab anything
if ("blockTag" in req && req.blockTag === "pending") {
return getAnyResult(this.quorum, results);
}
return checkQuorum(this.quorum, results);
case "call":
case "chainId":
case "getBalance":
case "getTransactionCount":
case "getCode":
case "getStorage":
case "getTransaction":
case "getTransactionReceipt":
case "getLogs":
return checkQuorum(this.quorum, results);
case "broadcastTransaction":
return getAnyResult(this.quorum, results);
}
assert(false, "unsupported method", "UNSUPPORTED_OPERATION", {
operation: `_perform(${ stringify((<any>req).method) })`
});
}
async #waitForQuorum(running: Set<RunnerState>, req: PerformActionRequest): Promise<any> {
if (running.size === 0) { throw new Error("no runners?!"); }
// Any promises that are interesting to watch for; an expired stall
// or a successful perform
const interesting: Array<Promise<void>> = [ ];
let newRunners = 0;
for (const runner of running) {
// No responses, yet; keep an eye on it
if (runner.perform) {
interesting.push(runner.perform);
}
// Still stalling...
if (runner.staller) {
interesting.push(runner.staller);
continue;
}
// This runner has already triggered another runner
if (runner.didBump) { continue; }
// Got a response (result or error) or stalled; kick off another runner
runner.didBump = true;
newRunners++;
}
// Check if we have reached quorum on a result (or error)
const value = await this.#checkQuorum(running, req);
if (value !== undefined) {
if (value instanceof Error) { throw value; }
return value;
}
// Add any new runners, because a staller timed out or a result
// or error response came in.
for (let i = 0; i < newRunners; i++) {
this.#addRunner(running, req);
}
// All providers have returned, and we have no result
assert(interesting.length > 0, "quorum not met", "SERVER_ERROR", {
request: "%sub-requests",
info: { request: req, results: Array.from(running).map((r) => stringify(r.result)) }
});
// Wait for someone to either complete its perform or stall out
await Promise.race(interesting);
// This is recursive, but at worst case the depth is 2x the
// number of providers (each has a perform and a staller)
return await this.#waitForQuorum(running, req);
}
async _perform<T = any>(req: PerformActionRequest): Promise<T> {
// Broadcasting a transaction is rare (ish) and already incurs
// a cost on the user, so spamming is safe-ish. Just send it to
// every backend.
if (req.method === "broadcastTransaction") {
// 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);
results[index] = Object.assign(normalizeResult(req.method, { result }), { weight });
} catch (error: any) {
results[index] = Object.assign(normalizeResult(req.method, { 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);
}
// 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) }
})
if (result instanceof Error) { throw result; }
return result;
}
await this.#initialSync();
// Bootstrap enough runners to meet quorum
const running: Set<RunnerState> = new Set();
let inflightQuorum = 0;
while (true) {
const runner = this.#addRunner(running, req);
if (runner == null) { break; }
inflightQuorum += runner.config.weight;
if (inflightQuorum >= this.quorum) { break; }
}
const result = await this.#waitForQuorum(running, req);
// Track requests sent to a provider that are still
// outstanding after quorum has been otherwise found
for (const runner of running) {
if (runner.perform && runner.result == null) {
runner.config.lateResponses++;
}
}
return result;
}
async destroy(): Promise<void> {
for (const { provider } of this.#configs) {
provider.destroy();
}
super.destroy();
}
}
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