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import moment from 'moment';
import { hasExpired } from '../shared/account-expiry';
import { AccountToken, IAccountData } from '../shared/daemon-rpc-types';
import log from '../shared/logging';
import consumePromise from '../shared/promise';
import { Scheduler } from '../shared/scheduler';
import { InvalidAccountError } from './errors';
const EXPIRED_ACCOUNT_REFRESH_PERIOD = 60_000;
interface IAccountFetchWatcher {
onFinish: () => void;
onError: (error: Error) => void;
}
// An account data cache that helps to throttle RPC requests to get_account_data and retain the
// cached value for 1 minute.
export default class AccountDataCache {
private currentAccount?: AccountToken;
private expiresAt?: Date;
private performingFetch = false;
private waitStrategy = new WaitStrategy();
private fetchRetryScheduler = new Scheduler();
private watchers: IAccountFetchWatcher[] = [];
constructor(
private fetchHandler: (token: AccountToken) => Promise<IAccountData>,
private updateHandler: (data?: IAccountData) => void,
) {}
public fetch(accountToken: AccountToken, watcher?: IAccountFetchWatcher) {
// invalidate cache if account token has changed
if (accountToken !== this.currentAccount) {
this.invalidate();
this.currentAccount = accountToken;
}
// Only fetch if value has expired
if (this.isExpired()) {
if (watcher) {
this.watchers.push(watcher);
}
this.fetchRetryScheduler.cancel();
// If a scheduled retry is cancelled the fetchAttempt shouldn't be increased.
this.waitStrategy.decrease();
// Only fetch if there's no fetch for this account number in progress.
if (!this.performingFetch) {
consumePromise(this.performFetch(accountToken));
}
} else if (watcher) {
watcher.onFinish();
}
}
public invalidate() {
this.fetchRetryScheduler.cancel();
this.waitStrategy.reset();
this.performingFetch = false;
this.expiresAt = undefined;
this.updateHandler();
this.notifyWatchers((watcher) => {
watcher.onError(new Error('Cancelled'));
});
}
private setValue(value: IAccountData) {
this.expiresAt = new Date(Date.now() + 60 * 1000); // 60s expiration
this.updateHandler(value);
this.notifyWatchers((watcher) => watcher.onFinish());
}
private isExpired() {
return !this.expiresAt || this.expiresAt < new Date();
}
private async performFetch(accountToken: AccountToken) {
this.performingFetch = true;
try {
// it's possible for invalidate() to be called or for a fetch for a different account token
// to start before this fetch completes, so checking if the current account token is the one
// used is necessary below.
const accountData = await this.fetchHandler(accountToken);
if (this.currentAccount === accountToken) {
this.setValue(accountData);
const refetchDelay = this.calculateRefetchDelay(accountData.expiry);
if (refetchDelay) {
this.scheduleFetch(accountToken, refetchDelay);
}
this.waitStrategy.reset();
this.performingFetch = false;
}
} catch (error) {
if (this.currentAccount === accountToken) {
this.handleFetchError(accountToken, error);
this.performingFetch = false;
}
}
}
private calculateRefetchDelay(accountExpiry: string) {
const currentDate = new Date();
const oneMinuteBeforeExpiry = moment(accountExpiry).subtract(1, 'minute');
const closeToExpiry = moment(accountExpiry).isSameOrBefore(moment().add(3, 'days'));
if (hasExpired(accountExpiry)) {
return EXPIRED_ACCOUNT_REFRESH_PERIOD;
} else if (oneMinuteBeforeExpiry.isSameOrAfter(currentDate) && closeToExpiry) {
return oneMinuteBeforeExpiry.diff(currentDate);
} else {
return undefined;
}
}
private handleFetchError(accountToken: AccountToken, error: Error) {
this.notifyWatchers((w) => w.onError(error));
if (!(error instanceof InvalidAccountError)) {
this.scheduleRetry(accountToken);
}
}
private scheduleRetry(accountToken: AccountToken) {
this.waitStrategy.increase();
const delay = this.waitStrategy.delay();
log.warn(`Failed to fetch account data. Retrying in ${delay} ms`);
this.scheduleFetch(accountToken, delay);
}
private scheduleFetch(accountToken: AccountToken, delay: number) {
this.fetchRetryScheduler.schedule(() => {
consumePromise(this.performFetch(accountToken));
}, delay);
}
private notifyWatchers(notify: (watcher: IAccountFetchWatcher) => void) {
this.watchers.splice(0).forEach(notify);
}
}
const MAX_ATTEMPT = 9;
class WaitStrategy {
private counter = 0;
public increase() {
if (this.counter < MAX_ATTEMPT) {
this.counter += 1;
}
}
public decrease() {
if (this.counter > 0) {
this.counter -= 1;
}
}
public reset() {
this.counter = 0;
}
public delay(): number {
// Max delay: 2^11 = 2048
return Math.pow(2, this.counter + 2) * 1000;
}
}
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