Exports an object to set as Winston `defaultMeta` (do not use Object.assign to merge with other default metadata first)

stackdriver-logging-winston-default-meta.js

let stackdriverLoggingWinston = null;
try {
  stackdriverLoggingWinston = require('@google-cloud/logging-winston');
} catch (e) {}

const agent = global._google_trace_agent;

const enableThunkTimestamp = !!stackdriverLoggingWinston;
const enableThunkAgent = !!(stackdriverLoggingWinston
  && stackdriverLoggingWinston.LOGGING_TRACE_KEY
  && agent && agent.getCurrentContextId && agent.getWriterProjectId);

const defaultMeta = {};

if (enableThunkTimestamp) {
  Object.defineProperty(defaultMeta, 'timestamp', {
    enumerable: true,
    get: () => new Date()
  });
}
if (enableThunkAgent) {
  const loggingTraceKey = stackdriverLoggingWinston.LOGGING_TRACE_KEY;
  Object.defineProperty(defaultMeta, loggingTraceKey, {
    enumerable: true,
    get: () => {
      const traceId = agent.getCurrentContextId();
      if (!traceId) {
        return null;
      }
    
      const traceProjectId = agent.getWriterProjectId();
      if (!traceProjectId) {
        return null;
      }
    
      return `projects/${traceProjectId}/traces/${traceId}`;
    }
  });
}

module.exports = defaultMeta;