@hatsa/express/log.js

const expressWinston = require('express-winston'); // https://github.com/bithavoc/express-winston
const uuidv1         = require('uuid/v1');
const { lw }         = require('@hatsa/log/transports/googlecloud');

const createRequestLogger = ({logger}) => expressWinston.logger({
    winstonInstance: logger,
    expressFormat: true,
    metaField: null, //'express',
    meta: true,
    ignoreRoute: req => {

        if (req.path.startsWith('/assets/'))
            return true;

        if (req.path.startsWith('/static/'))
            return true;

        return false;
    }
});

const createErrorLogger = ({logger}) => expressWinston.errorLogger({
    winstonInstance: logger,
    metaField: null, //'express',
    // dumpExceptions: true,
    // showStack: false,
    msg: "{{err.message}}", //msg: i can be a function too!
    // expressFormat: true,
    level: 'error' //var level = _.isFunction(options.level) ? options.level(req, res, err) : options.level;
});

const loggerMiddleware = ({logger}) => (req, res, next) => {

    const traceHeader = req.get('x-cloud-trace-context') || '';
    const traceId = traceHeader.includes('/') ? traceHeader.split('/')[0] : undefined;

    const aeReqId = req.get('x-appengine-request-log-id');
    const cfReqId = req.get('function-execution-id');
    const reqId = aeReqId || cfReqId || uuidv1();

    const meta = { labels: { execution_id: reqId } };

    // Poor mans tracing alternative (non promise based like sd_mw). Does this work?
    if (traceId)
        meta['logging.googleapis.com/trace'] = `projects/hatsa-tst-01/traces/${traceId}`;

    req.log = logger.child(meta);

    next();

    /**
        Poor mans alternative (non promise based like sd_mw):

        Header from App-Engine:
        x-cloud-trace-context: "71d942f0a6ad4ac9acf48da79c0361ed/10502738401706661831;o=1"

        Meaning (https://cloud.google.com/trace/docs/troubleshooting):
        x-cloud-trace-context: TRACE_ID/SPAN_ID;o=TRACE_TRUE

        Log metadata to key-values set:
        'logging.googleapis.com/trace': `projects/${PROJECT_ID}/traces/${TRACE_ID}`;
        'logging.googleapis.com/trace': 'projects/hatsa-tst-01/traces/71d942f0a6ad4ac9acf48da79c0361ed'
    */
};

const genStackdriverLogTraceMw = logger => lw.express.makeMiddleware(logger);

module.exports = {
    createRequestLogger,
    createErrorLogger,
    loggerMiddleware,
    genStackdriverLogTraceMw
};