mongochangestream/dist/safelyCheckNext.js

Sync MongoDB collections via change streams into any database.

import _debug from 'debug';
const debug = _debug('mongochangestream:safelyCheckNext');
/**
 * Get next record without throwing an exception.
 * Get the last error safely via `getLastError`.
 */
export const safelyCheckNext = (cursor) => {
    debug('safelyCheckNext called');
    let lastError;
    // Returns the next record, or null if there are no more records.
    //
    // NOTE: In the event that there are no more records, this will still block
    // for a minute or so, until there is a "no-op" event in the oplog. At that
    // point, it will return null and a fresh resume token can be retrieved from
    // the change stream object.
    //
    // Also returns null if there was an error, so it's important to check if
    // there was an error afterwards via `errorExists()` and/or `getLastError()`.
    const getNext = async () => {
        debug('getNext called');
        try {
            return await cursor.tryNext();
        }
        catch (e) {
            debug('getNext error: %o', e);
            lastError = e;
            return null;
        }
    };
    const errorExists = () => Boolean(lastError);
    const getLastError = () => lastError;
    return { getNext, errorExists, getLastError };
};