RecurringOperation.js

/* eslint-disable no-underscore-dangle */

module.exports = ({
  processEventEmitter,
  logger,
  skipRecurringOperationRefetch,
}) =>
  class RecurringOperation {
    constructor({ operation, expiry = null }) {
      if (typeof operation !== 'function') {
        throw new TypeError('Option `operation` has to be a function.');
      }
      if (expiry && typeof expiry !== 'function') {
        throw new TypeError(
          'Option `operation` has to be a function or falsy.',
        );
      }
      this._operation = operation;
      this._expiry = expiry;
      this._listeningOnSigterm = false;
    }

    _listenOnSigterm() {
      if (this._listeningOnSigterm) {
        return;
      }
      this._listeningOnSigterm = true;

      processEventEmitter.on('SIGTERM', () => {
        clearTimeout(this._refreshTimer);
        this._refreshTimer = null;
        this._promise = null;
      });
    }

    _scheduleNextRun(result) {
      if (!this._expiry || skipRecurringOperationRefetch) {
        return;
      }

      const expiry = this._expiry(result);

      if (typeof expiry === 'number' && expiry > 0) {
        this._refreshTimer = setTimeout(() => this.refresh(), expiry);
        this._listenOnSigterm();
      } else {
        logger.warn(
          `RecurringOperation: Unable to resolve valid expiry. Got "${
            expiry
          }" - expected number > 0`,
        );
      }
    }

    async refresh() {
      try {
        this._promise = this._operation();
        const result = await this._promise;

        this._scheduleNextRun(result);
      } catch (err) {
        this._promise = null;
        logger.warn({ err }, `RecurringOperation: Failed executing operation.`);
      }
    }

    async execute() {
      if (!this._promise) {
        this.refresh();
      }

      return this._promise;
    }
  };