479 lines
17 KiB
TypeScript
479 lines
17 KiB
TypeScript
"use strict";
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import { Network } from "@ethersproject/networks";
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import { BlockWithTransactions, Provider } from "@ethersproject/abstract-provider";
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import { shuffled } from "@ethersproject/random";
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import { deepCopy, defineReadOnly, shallowCopy } from "@ethersproject/properties";
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import { BigNumber } from "@ethersproject/bignumber";
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import { Logger } from "@ethersproject/logger";
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import { version } from "./_version";
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const logger = new Logger(version);
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import { BaseProvider } from "./base-provider";
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function now() { return (new Date()).getTime(); }
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// Returns to network as long as all agree, or null if any is null.
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// Throws an error if any two networks do not match.
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function checkNetworks(networks: Array<Network>): Network {
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let result = null;
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for (let i = 0; i < networks.length; i++) {
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const network = networks[i];
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// Null! We do not know our network; bail.
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if (network == null) { return null; }
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if (result) {
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// Make sure the network matches the previous networks
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if (!(result.name === network.name && result.chainId === network.chainId &&
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((result.ensAddress === network.ensAddress) || (result.ensAddress == null && network.ensAddress == null)))) {
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logger.throwArgumentError("provider mismatch", "networks", networks);
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}
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} else {
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result = network;
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}
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}
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return result;
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}
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function median(values: Array<number>): number {
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values = values.slice().sort();
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const middle = Math.floor(values.length / 2);
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// Odd length; take the middle
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if (values.length % 2) {
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return values[middle];
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}
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// Even length; take the average of the two middle
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const a = values[middle - 1], b = values[middle];
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return (a + b) / 2;
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}
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function serialize(value: any): string {
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if (value === null) {
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return null;
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} else if (typeof(value) === "number" || typeof(value) === "boolean") {
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return JSON.stringify(value);
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} else if (typeof(value) === "string") {
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return value;
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} else if (BigNumber.isBigNumber(value)) {
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return value.toString();
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} else if (Array.isArray(value)) {
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return JSON.stringify(value.map((i) => serialize(i)));
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} else if (typeof(value) === "object") {
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const keys = Object.keys(value);
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keys.sort();
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return "{" + keys.map((key) => {
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let v = value[key];
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if (typeof(v) === "function") {
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v = "[function]";
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} else {
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v = serialize(v);
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}
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return JSON.stringify(key) + ":" + v;
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}).join(",") + "}";
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}
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throw new Error("unknown value type: " + typeof(value));
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}
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// Next request ID to use for emitting debug info
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let nextRid = 1;
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export interface FallbackProviderConfig {
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// The Provider
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provider: Provider;
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// The priority to favour this Provider; higher values are used first
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priority?: number;
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// Timeout before also triggering the next provider; this does not stop
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// this provider and if its result comes back before a quorum is reached
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// it will be used it will be used.
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// - lower values will cause more network traffic but may result in a
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// faster retult.
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stallTimeout?: number;
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// How much this provider contributes to the quorum; sometimes a specific
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// provider may be more reliable or trustworthy than others, but usually
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// this should be left as the default
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weight?: number;
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};
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// Returns a promise that delays for duration
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function stall(duration: number): Promise<void> {
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return new Promise((resolve) => {
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const timer = setTimeout(resolve, duration);
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if (timer.unref) { timer.unref(); }
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});
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}
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interface RunningConfig extends FallbackProviderConfig {
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start?: number;
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done?: boolean;
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runner?: Promise<any>;
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staller?: Promise<void>;
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result?: any;
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error?: Error;
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};
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function exposeDebugConfig(config: RunningConfig, now?: number): any {
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const result: any = {
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provider: config.provider,
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weight: config.weight
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};
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if (config.start) { result.start = config.start; }
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if (now) { result.duration = (now - config.start); }
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if (config.done) {
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if (config.error) {
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result.error = config.error;
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} else {
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result.result = config.result || null;
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}
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}
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return result;
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}
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function normalizedTally(normalize: (value: any) => string, quorum: number): (configs: Array<RunningConfig>) => any {
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return function(configs: Array<RunningConfig>): any {
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// Count the votes for each result
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const tally: { [ key: string]: { count: number, result: any } } = { };
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configs.forEach((c) => {
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const value = normalize(c.result);
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if (!tally[value]) { tally[value] = { count: 0, result: c.result }; }
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tally[value].count++;
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});
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// Check for a quorum on any given result
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const keys = Object.keys(tally);
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for (let i = 0; i < keys.length; i++) {
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const check = tally[keys[i]];
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if (check.count >= quorum) {
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return check.result;
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}
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}
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// No quroum
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return undefined;
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}
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}
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function getProcessFunc(provider: FallbackProvider, method: string, params: { [ key: string ]: any }): (configs: Array<RunningConfig>) => any {
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let normalize = serialize;
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switch (method) {
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case "getBlockNumber":
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// Return the median value, unless there is (median + 1) is also
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// present, in which case that is probably true and the median
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// is going to be stale soon. In the event of a malicious node,
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// the lie will be true soon enough.
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return function(configs: Array<RunningConfig>): number {
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const values = configs.map((c) => c.result);
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// Get the median block number
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let blockNumber = Math.ceil(median(configs.map((c) => c.result)));
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// If the next block height is present, its prolly safe to use
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if (values.indexOf(blockNumber + 1) >= 0) { blockNumber++; }
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// Don't ever roll back the blockNumber
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if (blockNumber >= provider._highestBlockNumber) {
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provider._highestBlockNumber = blockNumber;
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}
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return provider._highestBlockNumber;
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};
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case "getGasPrice":
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// Return the middle (round index up) value, similar to median
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// but do not average even entries and choose the higher.
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// Malicious actors must compromise 50% of the nodes to lie.
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return function(configs: Array<RunningConfig>): BigNumber {
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const values = configs.map((c) => c.result);
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values.sort();
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return values[Math.floor(values.length / 2)];
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}
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case "getEtherPrice":
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// Returns the median price. Malicious actors must compromise at
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// least 50% of the nodes to lie (in a meaningful way).
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return function(configs: Array<RunningConfig>): number {
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return median(configs.map((c) => c.result));
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}
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// No additional normalizing required; serialize is enough
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case "getBalance":
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case "getTransactionCount":
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case "getCode":
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case "getStorageAt":
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case "call":
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case "estimateGas":
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case "getLogs":
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break;
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// We drop the confirmations from transactions as it is approximate
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case "getTransaction":
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case "getTransactionReceipt":
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normalize = function(tx: any): string {
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tx = shallowCopy(tx);
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tx.confirmations = -1;
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return serialize(tx);
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}
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break;
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// We drop the confirmations from transactions as it is approximate
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case "getBlock":
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// We drop the confirmations from transactions as it is approximate
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if (params.includeTransactions) {
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normalize = function(block: BlockWithTransactions): string {
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block = shallowCopy(block);
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block.transactions = block.transactions.map((tx) => {
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tx = shallowCopy(tx);
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tx.confirmations = -1;
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return tx;
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});
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return serialize(block);
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};
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}
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break;
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default:
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throw new Error("unknown method: " + method);
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}
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// Return the result if and only if the expected quorum is
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// satisfied and agreed upon for the final result.
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return normalizedTally(normalize, provider.quorum);
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}
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function getRunner(provider: Provider, method: string, params: { [ key: string]: any }): Promise<any> {
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switch (method) {
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case "getBlockNumber":
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case "getGasPrice":
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return provider[method]();
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case "getEtherPrice":
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if ((<any>provider).getEtherPrice) {
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return (<any>provider).getEtherPrice();
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}
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break;
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case "getBalance":
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case "getTransactionCount":
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case "getCode":
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return provider[method](params.address, params.blockTag || "latest");
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case "getStorageAt":
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return provider.getStorageAt(params.address, params.position, params.blockTag || "latest");
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case "getBlock":
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return provider[(params.includeTransactions ? "getBlockWithTransactions": "getBlock")](params.blockTag || params.blockHash);
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case "call":
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case "estimateGas":
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return provider[method](params.transaction);
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case "getTransaction":
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case "getTransactionReceipt":
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return provider[method](params.transactionHash);
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case "getLogs":
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return provider.getLogs(params.filter);
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}
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return logger.throwError("unknown method error", Logger.errors.UNKNOWN_ERROR, {
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method: method,
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params: params
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});
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}
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export class FallbackProvider extends BaseProvider {
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readonly providerConfigs: Array<FallbackProviderConfig>;
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readonly quorum: number;
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// Due to teh highly asyncronous nature of the blockchain, we need
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// to make sure we never unroll the blockNumber due to our random
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// sample of backends
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_highestBlockNumber: number;
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constructor(providers: Array<Provider | FallbackProviderConfig>, quorum?: number) {
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logger.checkNew(new.target, FallbackProvider);
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if (providers.length === 0) {
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logger.throwArgumentError("missing providers", "providers", providers);
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}
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const providerConfigs: Array<FallbackProviderConfig> = providers.map((configOrProvider, index) => {
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if (Provider.isProvider(configOrProvider)) {
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return Object.freeze({ provider: configOrProvider, weight: 1, stallTimeout: 750, priority: 1 });
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}
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const config: FallbackProviderConfig = shallowCopy(configOrProvider);
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if (config.priority == null) { config.priority = 1; }
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if (config.stallTimeout == null) { config.stallTimeout = 750; }
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if (config.weight == null) { config.weight = 1; }
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const weight = config.weight;
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if (weight % 1 || weight > 512 || weight < 1) {
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logger.throwArgumentError("invalid weight; must be integer in [1, 512]", `providers[${ index }].weight`, weight);
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}
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return Object.freeze(config);
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});
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const total = providerConfigs.reduce((accum, c) => (accum + c.weight), 0);
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if (quorum == null) {
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quorum = total / 2;
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} else if (quorum > total) {
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logger.throwArgumentError("quorum will always fail; larger than total weight", "quorum", quorum);
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}
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// All networks are ready, we can know the network for certain
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const network = checkNetworks(providerConfigs.map((c) => (<any>(c.provider)).network));
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if (network) {
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super(network);
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} else {
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// The network won't be known until all child providers know
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const ready = Promise.all(providerConfigs.map((c) => c.provider.getNetwork())).then((networks) => {
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return checkNetworks(networks);
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});
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super(ready);
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}
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// Preserve a copy, so we do not get mutated
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defineReadOnly(this, "providerConfigs", Object.freeze(providerConfigs));
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defineReadOnly(this, "quorum", quorum);
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this._highestBlockNumber = -1;
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}
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async perform(method: string, params: { [name: string]: any }): Promise<any> {
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// Sending transactions is special; always broadcast it to all backends
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if (method === "sendTransaction") {
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return Promise.all(this.providerConfigs.map((c) => {
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return c.provider.sendTransaction(params.signedTransaction).then((result) => {
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return result.hash;
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}, (error) => {
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return error;
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});
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})).then((results) => {
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// Any success is good enough (other errors are likely "already seen" errors
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for (let i = 0; i < results.length; i++) {
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const result = results[i];
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if (typeof(result) === "string") { return result; }
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}
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// They were all an error; pick the first error
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return Promise.reject(results[0].error);
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});
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}
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const processFunc = getProcessFunc(this, method, params);
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// Shuffle the providers and then sort them by their priority; we
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// shallowCopy them since we will store the result in them too
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const configs: Array<RunningConfig> = shuffled(this.providerConfigs.map((c) => shallowCopy(c)));
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configs.sort((a, b) => (a.priority - b.priority));
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let i = 0;
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while (true) {
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const t0 = now();
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// Get a list of running
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//const running = configs.filter((c) => (c.runner && !c.done));
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// Compute the inflight weight (exclude anything past)
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let inflightWeight = configs.filter((c) => (c.runner && ((t0 - c.start) < c.stallTimeout)))
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.reduce((accum, c) => (accum + c.weight), 0);
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// Start running enough to meet quorum
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while (inflightWeight < this.quorum && i < configs.length) {
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const config = configs[i++];
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const rid = nextRid++;
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config.start = now();
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config.staller = stall(config.stallTimeout).then(() => { config.staller = null; });
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config.runner = getRunner(config.provider, method, params).then((result) => {
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config.done = true;
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config.result = result;
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if (this.listenerCount("debug")) {
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this.emit("debug", {
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action: "request",
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rid: rid,
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backend: exposeDebugConfig(config, now()),
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request: { method: method, params: deepCopy(params) },
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provider: this
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});
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}
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}, (error) => {
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config.done = true;
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config.error = error;
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if (this.listenerCount("debug")) {
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this.emit("debug", {
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action: "request",
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rid: rid,
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backend: exposeDebugConfig(config, now()),
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request: { method: method, params: deepCopy(params) },
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provider: this
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});
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}
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});
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//running.push(config);
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if (this.listenerCount("debug")) {
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this.emit("debug", {
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action: "request",
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rid: rid,
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backend: exposeDebugConfig(config, null),
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request: { method: method, params: deepCopy(params) },
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provider: this
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});
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}
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inflightWeight += config.weight;
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}
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// Wait for anything meaningful to finish or stall out
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const waiting: Array<Promise<any>> = [ ];
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configs.forEach((c) => {
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if (c.done || !c.runner) { return; }
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waiting.push(c.runner);
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if (c.staller) { waiting.push(c.staller); }
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});
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if (waiting.length) { await Promise.race(waiting); }
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// Check the quorum and process the results; the process function
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// may additionally decide the quorum is not met
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const results = configs.filter((c) => (c.done && c.error == null));
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if (results.length >= this.quorum) {
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const result = processFunc(results);
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if (result != undefined) { return result; }
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}
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// All configs have run to completion; we will never get more data
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if (configs.filter((c) => !c.done).length === 0) { break; }
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}
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return logger.throwError("failed to meet quorum", Logger.errors.SERVER_ERROR, {
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method: method,
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params: params,
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results: configs.map((c) => exposeDebugConfig(c)),
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//errors: configs.map((c) => c.error),
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provider: this
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});
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}
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}
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