Much more resiliant FallbackProvider which can ignore properties that are only approximate and supports per-provider priorities (#635, #588).

This commit is contained in:
Richard Moore 2020-01-18 21:24:28 -05:00
parent ea102ef7c4
commit f4bcf24a25
No known key found for this signature in database
GPG Key ID: 665176BE8E9DC651
2 changed files with 411 additions and 243 deletions

@ -687,6 +687,23 @@ export class BaseProvider extends Provider {
// Add transactions
if (includeTransactions) {
let blockNumber: number = null;
for (let i = 0; i < block.transactions.length; i++) {
const tx = block.transactions[i];
if (tx.blockNumber == null) {
tx.confirmations = 0;
} else if (tx.confirmations == null) {
if (blockNumber == null) {
blockNumber = await this._getInternalBlockNumber(100 + 2 * this.pollingInterval);
}
// Add the confirmations using the fast block number (pessimistic)
let confirmations = (blockNumber - tx.blockNumber) + 1;
if (confirmations <= 0) { confirmations = 1; }
tx.confirmations = confirmations;
}
}
return this.formatter.blockWithTransactions(block);
}
@ -777,7 +794,10 @@ export class BaseProvider extends Provider {
async getLogs(filter: Filter | FilterByBlockHash | Promise<Filter | FilterByBlockHash>): Promise<Array<Log>> {
await this.ready;
const params = await resolveProperties({ filter: this._getFilter(filter) });
const logs = await this.perform("getLogs", params);
const logs: Array<Log> = await this.perform("getLogs", params);
logs.forEach((log) => {
if (log.removed == null) { log.removed = false; }
});
return Formatter.arrayOf(this.formatter.filterLog.bind(this.formatter))(logs);
}

@ -1,8 +1,9 @@
"use strict";
import { Network } from "@ethersproject/networks";
import { BlockWithTransactions, Provider } from "@ethersproject/abstract-provider";
import { shuffled } from "@ethersproject/random";
import { deepCopy, defineReadOnly } from "@ethersproject/properties";
import { deepCopy, defineReadOnly, shallowCopy } from "@ethersproject/properties";
import { BigNumber } from "@ethersproject/bignumber";
import { Logger } from "@ethersproject/logger";
@ -13,150 +14,262 @@ import { BaseProvider } from "./base-provider";
function now() { return (new Date()).getTime(); }
// Returns:
// - true is all networks match
// - false if any network is null
// - throws if any 2 networks do not match
function checkNetworks(networks: Array<Network>): boolean {
let result = true;
// Returns to network as long as all agree, or null if any is null.
// Throws an error if any two networks do not match.
function checkNetworks(networks: Array<Network>): Network {
let result = null;
let check: Network = null;
networks.forEach((network) => {
for (let i = 0; i < networks.length; i++) {
const network = networks[i];
// Null
if (network == null) {
result = false;
return;
}
// Null! We do not know our network; bail.
if (network == null) { return null; }
// Have nothing to compre to yet
if (check == null) {
check = network;
return;
}
// Matches!
if (check.name === network.name &&
check.chainId === network.chainId &&
((check.ensAddress === network.ensAddress) ||
(check.ensAddress == null && network.ensAddress == null))) { return; }
if (result) {
// Make sure the network matches the previous networks
if (!(result.name === network.name && result.chainId === network.chainId &&
((result.ensAddress === network.ensAddress) || (result.ensAddress == null && network.ensAddress == null)))) {
logger.throwArgumentError("provider mismatch", "networks", networks);
});
}
} else {
result = network;
}
}
return result;
}
type Result = {
result?: any;
error?: Error;
weight: number;
};
function median(values: Array<number>): number {
values = values.slice().sort();
const middle = Math.floor(values.length / 2);
type Runner = {
run: () => Promise<Result>;
weight: number;
};
// Odd length; take the middle
if (values.length % 2) {
return values[middle];
}
// Even length; take the average of the two middle
const a = values[middle - 1], b = values[middle];
return (a + b) / 2;
}
function serialize(result: any): string {
if (Array.isArray(result)) {
return JSON.stringify(result.map((r) => serialize(r)));
} else if (result === null) {
return "null";
} else if (typeof(result) === "object") {
let keys = Object.keys(result);
function serialize(value: any): string {
if (value === null) {
return null;
} else if (typeof(value) === "number" || typeof(value) === "boolean") {
return JSON.stringify(value);
} else if (typeof(value) === "string") {
return value;
} else if (BigNumber.isBigNumber(value)) {
return value.toString();
} else if (Array.isArray(value)) {
return JSON.stringify(value.map((i) => serialize(i)));
} else if (typeof(value) === "object") {
const keys = Object.keys(value);
keys.sort();
return "{" + keys.map((key) => {
let value = result[key];
if (typeof(value) === "function") {
value = "function{}";
let v = value[key];
if (typeof(v) === "function") {
v = "[function]";
} else {
value = serialize(value);
v = serialize(v);
}
return JSON.stringify(key) + "=" + serialize(value);
return JSON.stringify(key) + ":" + v;
}).join(",") + "}";
}
return JSON.stringify(result);
throw new Error("unknown value type: " + typeof(value));
}
// Next request ID to use for emitting debug info
let nextRid = 1;
export class FallbackProvider extends BaseProvider {
readonly providers: Array<BaseProvider>;
readonly weights: Array<number>;
readonly quorum: number;
constructor(providers: Array<BaseProvider>, quorum?: number, weights?: Array<number>) {
logger.checkNew(new.target, FallbackProvider);
export interface FallbackProviderConfig {
// The Provider
provider: Provider;
if (providers.length === 0) {
logger.throwArgumentError("missing providers", "providers", providers);
}
// The priority to favour this Provider; higher values are used first
priority?: number;
if (weights != null && weights.length !== providers.length) {
logger.throwArgumentError("too many weights", "weights", weights);
} else if (!weights) {
weights = providers.map((p) => 1);
} else {
weights.forEach((w) => {
if (w % 1 || w > 512 || w < 1) {
logger.throwArgumentError("invalid weight; must be integer in [1, 512]", "weights", weights);
}
// Timeout before also triggering the next provider; this does not stop
// this provider and if its result comes back before a quorum is reached
// it will be used it will be used.
// - lower values will cause more network traffic but may result in a
// faster retult.
stallTimeout?: number;
// How much this provider contributes to the quorum; sometimes a specific
// provider may be more reliable or trustworthy than others, but usually
// this should be left as the default
weight?: number;
};
// Returns a promise that delays for duration
function stall(duration: number): Promise<void> {
return new Promise((resolve) => {
const timer = setTimeout(resolve, duration);
if (timer.unref) { timer.unref(); }
});
}
}
let total = weights.reduce((accum, w) => (accum + w));
interface RunningConfig extends FallbackProviderConfig {
start?: number;
done?: boolean;
runner?: Promise<any>;
staller?: Promise<void>;
result?: any;
error?: Error;
};
if (quorum == null) {
quorum = total / 2;
function exposeDebugConfig(config: RunningConfig, now?: number): any {
const result: any = {
provider: config.provider,
weight: config.weight
};
if (config.start) { result.start = config.start; }
if (now) { result.duration = (now - config.start); }
if (config.done) {
if (config.error) {
result.error = config.error;
} else {
if (quorum > total) {
logger.throwArgumentError("quorum will always fail; larger than total weight", "quorum", quorum);
result.result = config.result || null;
}
}
return result;
}
function normalizedTally(normalize: (value: any) => string, quorum: number): (configs: Array<RunningConfig>) => any {
return function(configs: Array<RunningConfig>): any {
// All networks are ready, we can know the network for certain
let ready = checkNetworks(providers.map((p) => p.network));
if (ready) {
super(providers[0].network);
} else {
// The network won't be known until all child providers know
let ready = Promise.all(providers.map((p) => p.getNetwork())).then((networks) => {
if (!checkNetworks(networks)) {
logger.throwError("getNetwork returned null", Logger.errors.UNKNOWN_ERROR)
}
return networks[0];
// Count the votes for each result
const tally: { [ key: string]: { count: number, result: any } } = { };
configs.forEach((c) => {
const value = normalize(c.result);
if (!tally[value]) { tally[value] = { count: 0, result: c.result }; }
tally[value].count++;
});
super(ready);
// Check for a quorum on any given result
const keys = Object.keys(tally);
for (let i = 0; i < keys.length; i++) {
const check = tally[keys[i]];
if (check.count >= quorum) {
return check.result;
}
}
// Preserve a copy, so we do not get mutated
defineReadOnly(this, "providers", Object.freeze(providers.slice()));
defineReadOnly(this, "quorum", quorum);
defineReadOnly(this, "weights", Object.freeze(weights.slice()));
// No quroum
return undefined;
}
}
function getProcessFunc(provider: FallbackProvider, method: string, params: { [ key: string ]: any }): (configs: Array<RunningConfig>) => any {
let normalize = serialize;
switch (method) {
case "getBlockNumber":
// Return the median value, unless there is (median + 1) is also
// present, in which case that is probably true and the median
// is going to be stale soon. In the event of a malicious node,
// the lie will be true soon enough.
return function(configs: Array<RunningConfig>): number {
const values = configs.map((c) => c.result);
// Get the median block number
let blockNumber = Math.ceil(median(configs.map((c) => c.result)));
// If the next block height is present, its prolly safe to use
if (values.indexOf(blockNumber + 1) >= 0) { blockNumber++; }
// Don't ever roll back the blockNumber
if (blockNumber >= provider._highestBlockNumber) {
provider._highestBlockNumber = blockNumber;
}
static doPerform(provider: BaseProvider, method: string, params: { [ name: string ]: any }): Promise<any> {
return provider._highestBlockNumber;
};
case "getGasPrice":
// Return the middle (round index up) value, similar to median
// but do not average even entries and choose the higher.
// Malicious actors must compromise 50% of the nodes to lie.
return function(configs: Array<RunningConfig>): BigNumber {
const values = configs.map((c) => c.result);
values.sort();
return values[Math.floor(values.length / 2)];
}
case "getEtherPrice":
// Returns the median price. Malicious actors must compromise at
// least 50% of the nodes to lie (in a meaningful way).
return function(configs: Array<RunningConfig>): number {
return median(configs.map((c) => c.result));
}
// No additional normalizing required; serialize is enough
case "getBalance":
case "getTransactionCount":
case "getCode":
case "getStorageAt":
case "call":
case "estimateGas":
case "getLogs":
break;
// We drop the confirmations from transactions as it is approximate
case "getTransaction":
case "getTransactionReceipt":
normalize = function(tx: any): string {
tx = shallowCopy(tx);
tx.confirmations = -1;
return serialize(tx);
}
break;
// We drop the confirmations from transactions as it is approximate
case "getBlock":
// We drop the confirmations from transactions as it is approximate
if (params.includeTransactions) {
normalize = function(block: BlockWithTransactions): string {
block = shallowCopy(block);
block.transactions = block.transactions.map((tx) => {
tx = shallowCopy(tx);
tx.confirmations = -1;
return tx;
});
return serialize(block);
};
}
break;
default:
throw new Error("unknown method: " + method);
}
// Return the result if and only if the expected quorum is
// satisfied and agreed upon for the final result.
return normalizedTally(normalize, provider.quorum);
}
function getRunner(provider: Provider, method: string, params: { [ key: string]: any }): Promise<any> {
switch (method) {
case "getBlockNumber":
case "getGasPrice":
case "getEtherPrice":
return provider[method]();
case "getEtherPrice":
if ((<any>provider).getEtherPrice) {
return (<any>provider).getEtherPrice();
}
break;
case "getBalance":
case "getTransactionCount":
case "getCode":
return provider[method](params.address, params.blockTag || "latest");
case "getStorageAt":
return provider.getStorageAt(params.address, params.position, params.blockTag || "latest");
case "sendTransaction":
return provider.sendTransaction(params.signedTransaction).then((result) => {
return result.hash;
});
case "getBlock":
return provider[(params.includeTransactions ? "getBlockWithTransactions": "getBlock")](params.blockTag || params.blockHash);
case "call":
@ -168,163 +281,198 @@ export class FallbackProvider extends BaseProvider {
case "getLogs":
return provider.getLogs(params.filter);
}
return logger.throwError("unknown method error", Logger.errors.UNKNOWN_ERROR, {
method: method,
params: params
});
}
export class FallbackProvider extends BaseProvider {
readonly providerConfigs: Array<FallbackProviderConfig>;
readonly quorum: number;
// Due to teh highly asyncronous nature of the blockchain, we need
// to make sure we never unroll the blockNumber due to our random
// sample of backends
_highestBlockNumber: number;
constructor(providers: Array<Provider | FallbackProviderConfig>, quorum?: number) {
logger.checkNew(new.target, FallbackProvider);
if (providers.length === 0) {
logger.throwArgumentError("missing providers", "providers", providers);
}
perform(method: string, params: { [name: string]: any }): any {
let T0 = now();
let runners: Array<Runner> = (<Array<BaseProvider>>(shuffled(this.providers))).map((provider, i) => {
let weight = this.weights[i];
let rid = nextRid++;
return {
run: () => {
let t0 = now();
let start = t0 - T0;
this.emit("debug", {
action: "request",
rid: rid,
backend: { weight, start, provider },
request: { method: method, params: deepCopy(params) },
provider: this
});
return FallbackProvider.doPerform(provider, method, params).then((result) => {
let duration = now() - t0;
this.emit("debug", {
action: "response",
rid: rid,
backend: { weight, start, duration, provider },
request: { method: method, params: deepCopy(params) },
response: deepCopy(result)
});
return { weight: weight, result: result };
}, (error) => {
let duration = now() - t0;
this.emit("debug", {
action: "response",
rid: rid,
backend: { weight, start, duration, provider },
request: { method: method, params: deepCopy(params) },
error: error
});
return { weight: weight, error: error };
});
},
weight: weight
const providerConfigs: Array<FallbackProviderConfig> = providers.map((configOrProvider, index) => {
if (Provider.isProvider(configOrProvider)) {
return Object.freeze({ provider: configOrProvider, weight: 1, stallTimeout: 750, priority: 1 });
}
const config: FallbackProviderConfig = shallowCopy(configOrProvider);
if (config.priority == null) { config.priority = 1; }
if (config.stallTimeout == null) { config.stallTimeout = 750; }
if (config.weight == null) { config.weight = 1; }
const weight = config.weight;
if (weight % 1 || weight > 512 || weight < 1) {
logger.throwArgumentError("invalid weight; must be integer in [1, 512]", `providers[${ index }].weight`, weight);
}
return Object.freeze(config);
});
// Broadcast transactions to all backends, any that succeed is good enough
const total = providerConfigs.reduce((accum, c) => (accum + c.weight), 0);
if (quorum == null) {
quorum = total / 2;
} else if (quorum > total) {
logger.throwArgumentError("quorum will always fail; larger than total weight", "quorum", quorum);
}
// All networks are ready, we can know the network for certain
const network = checkNetworks(providerConfigs.map((c) => (<any>(c.provider)).network));
if (network) {
super(network);
} else {
// The network won't be known until all child providers know
const ready = Promise.all(providerConfigs.map((c) => c.provider.getNetwork())).then((networks) => {
return checkNetworks(networks);
});
super(ready);
}
// Preserve a copy, so we do not get mutated
defineReadOnly(this, "providerConfigs", Object.freeze(providerConfigs));
defineReadOnly(this, "quorum", quorum);
this._highestBlockNumber = -1;
}
async perform(method: string, params: { [name: string]: any }): Promise<any> {
// Sending transactions is special; always broadcast it to all backends
if (method === "sendTransaction") {
return Promise.all(runners.map((r) => r.run())).then((results) => {
return Promise.all(this.providerConfigs.map((c) => {
return c.provider.sendTransaction(params.signedTransaction).then((result) => {
return result.hash;
}, (error) => {
return error;
});
})).then((results) => {
// Any success is good enough (other errors are likely "already seen" errors
for (let i = 0; i < results.length; i++) {
let result = results[i];
if (result.result) { return result.result; }
const result = results[i];
if (typeof(result) === "string") { return result; }
}
// They were all an error; pick the first error
return Promise.reject(results[0].error);
});
}
// Otherwise query backends (randomly) until we have a quorum agreement
// on the correct result
return new Promise((resolve, reject) => {
let firstError: Error = null;
const processFunc = getProcessFunc(this, method, params);
// How much weight is inflight
let inflightWeight = 0;
// Shuffle the providers and then sort them by their priority; we
// shallowCopy them since we will store the result in them too
const configs: Array<RunningConfig> = shuffled(this.providerConfigs.map((c) => shallowCopy(c)));
configs.sort((a, b) => (a.priority - b.priority));
// All results, indexed by the serialized response.
let results: { [ unique: string ]: Array<Result> } = { };
let i = 0;
while (true) {
const t0 = now();
let next = () => {
if (runners.length === 0) { return; }
// Get a list of running
//const running = configs.filter((c) => (c.runner && !c.done));
let runner = runners.shift();
inflightWeight += runner.weight;
// Compute the inflight weight (exclude anything past)
let inflightWeight = configs.filter((c) => (c.runner && ((t0 - c.start) < c.stallTimeout)))
.reduce((accum, c) => (accum + c.weight), 0);
runner.run().then((result) => {
if (results === null) { return; }
inflightWeight -= runner.weight;
// Start running enough to meet quorum
while (inflightWeight < this.quorum && i < configs.length) {
const config = configs[i++];
if (result.error) {
if (firstError == null) { firstError = result.error; }
const rid = nextRid++;
} else {
let unique = serialize(result.result);
if (results[unique] == null) { results[unique] = []; }
results[unique].push(result);
config.start = now();
config.staller = stall(config.stallTimeout).then(() => { config.staller = null; });
// Do any results meet our quroum?
for (let u in results) {
let weight = results[u].reduce((accum, r) => (accum + r.weight), 0);
if (weight >= this.quorum) {
let result = results[u][0].result;
this.emit("debug", "quorum", -1, { weight, result })
resolve(result);
results = null;
return;
}
}
}
config.runner = getRunner(config.provider, method, params).then((result) => {
config.done = true;
config.result = result;
// Out of options; give up
if (runners.length === 0 && inflightWeight === 0) {
// @TODO: this might need some more thinking... Maybe only if half
// of the results contain non-error?
if (method === "getGasPrice") {
const values: Array<BigNumber> = [ ];
Object.keys(results).forEach((key) => {
results[key].forEach((result) => {
if (!result.result) { return; }
values.push(result.result);
if (this.listenerCount("debug")) {
this.emit("debug", {
action: "request",
rid: rid,
backend: exposeDebugConfig(config, now()),
request: { method: method, params: deepCopy(params) },
provider: this
});
});
values.sort((a, b) => {
if (a.lt(b)) { return -1; }
if (a.gt(b)) { return 1; }
return 0;
});
let index = parseInt(String(values.length / 2));
if (values.length % 2) {
resolve(values[index]);
return;
}
resolve(values[index - 1].add(values[index]).div(2));
return;
}
if (firstError === null) {
firstError = logger.makeError("failed to meet quorum", Logger.errors.SERVER_ERROR, {
results: Object.keys(results).map((u) => {
return {
}, (error) => {
config.done = true;
config.error = error;
if (this.listenerCount("debug")) {
this.emit("debug", {
action: "request",
rid: rid,
backend: exposeDebugConfig(config, now()),
request: { method: method, params: deepCopy(params) },
provider: this
});
}
});
//running.push(config);
if (this.listenerCount("debug")) {
this.emit("debug", {
action: "request",
rid: rid,
backend: exposeDebugConfig(config, null),
request: { method: method, params: deepCopy(params) },
provider: this
});
}
inflightWeight += config.weight;
}
// Wait for anything meaningful to finish or stall out
const waiting: Array<Promise<any>> = [ ];
configs.forEach((c) => {
if (c.done || !c.runner) { return; }
waiting.push(c.runner);
if (c.staller) { waiting.push(c.staller); }
});
if (waiting.length) { await Promise.race(waiting); }
// Check the quorum and process the results; the process function
// may additionally decide the quorum is not met
const results = configs.filter((c) => (c.done && c.error == null));
if (results.length >= this.quorum) {
const result = processFunc(results);
if (result != undefined) { return result; }
}
// All configs have run to completion; we will never get more data
if (configs.filter((c) => !c.done).length === 0) { break; }
}
return logger.throwError("failed to meet quorum", Logger.errors.SERVER_ERROR, {
method: method,
params: params,
result: u,
weight: results[u].reduce((accum, r) => (accum + r.weight), 0)
};
})
});
}
reject(firstError);
return;
}
// Queue up the next round
setTimeout(next, 0);
});
// Fire off requests until we could possibly meet quorum
if (inflightWeight < this.quorum) {
setTimeout(next, 0);
return;
}
}
// bootstrap firing requests
next();
results: configs.map((c) => exposeDebugConfig(c)),
//errors: configs.map((c) => c.error),
provider: this
});
}
}