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import promisify = require('es6-promisify');
import * as _ from 'lodash';
import RpcSubprovider = require('web3-provider-engine/subproviders/rpc');
import {JSONRPCPayload} from '../types';
import {Subprovider} from './subprovider';
export class RedundantRPCSubprovider extends Subprovider {
private rpcs: RpcSubprovider[];
private static async firstSuccessAsync(
rpcs: RpcSubprovider[], payload: JSONRPCPayload, next: () => void,
): Promise<any> {
let lastErr: Error|undefined;
for (const rpc of rpcs) {
try {
const data = await promisify(rpc.handleRequest.bind(rpc))(payload, next);
return data;
} catch (err) {
lastErr = err;
continue;
}
}
if (!_.isUndefined(lastErr)) {
throw lastErr;
}
}
constructor(endpoints: string[]) {
super();
this.rpcs = _.map(endpoints, endpoint => {
return new RpcSubprovider({
rpcUrl: endpoint,
});
});
}
public async handleRequest(payload: JSONRPCPayload, next: () => void,
end: (err?: Error, data?: any) => void): Promise<void> {
const rpcsCopy = this.rpcs.slice();
try {
const data = await RedundantRPCSubprovider.firstSuccessAsync(rpcsCopy, payload, next);
end(undefined, data);
} catch (err) {
end(err);
}
}
}
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