seq_stream.js

'use strict';

let stream = require('stream');
let seq = require('seq-logging');

let LEVEL_NAMES = {
  10: 'Verbose',
  20: 'Debug',
  30: 'Information',
  40: 'Warning',
  50: 'Error',
  60: 'Fatal'
};

class SeqStream extends stream.Writable {
  constructor(config) {
    super({ objectMode: true });
    let { additionalProperties, ...loggerConfig } = config == null ? {} : { ...config };
    loggerConfig.onError =
      loggerConfig.onError ||
      function (e) {
        console.error('[SeqStream] Log batch failed\n', e);
      };
    this._additionalProperties = additionalProperties;
    this._logger = new seq.Logger(loggerConfig);
  }

  _write(logEntry, enc, cb) {
    if (logEntry) {
      let { time, level, msg, err, error, stack, v, ...props } = logEntry;

      // Get the properties from the error
      let { message: errMessage, stack: errStack, ...errorProps } = err || error || {};
      const seqEntry = {
        timestamp: new Date(time),
        level: LEVEL_NAMES[level],
        messageTemplate: msg ? msg : errMessage,
        properties: { ...errorProps, ...props, ...this._additionalProperties },
        exception: stack ? stack : errStack
      };

      try {
        this._logger.emit(seqEntry);
      } catch (err) {
        console.error(err, seqEntry);
      }
    }
    cb();
  }

  // Force the underlying logger to flush at the time of the call
  // and wait for pending writes to complete
  _final(callback) {
    this._logger
      .close()
      .then(() => callback())
      .catch((err) => callback(err));
  }
}

module.exports = SeqStream;