index.js

// Licensed to Elasticsearch B.V. under one or more contributor
// license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright
// ownership. Elasticsearch B.V. licenses this file to you under
// the Apache License, Version 2.0 (the "License"); you may
// not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

'use strict'

const morgan = require('morgan')
const safeStableStringify = require('safe-stable-stringify')
const {
  version,
  formatHttpRequest,
  formatHttpResponse
} = require('@elastic/ecs-helpers')

// We will query the Elastic APM agent if it is available.
let elasticApm = null
try {
  elasticApm = require('elastic-apm-node')
} catch (ex) {
  // Silently ignore.
}

const stringify = safeStableStringify.configure({ deterministic: false })

// Return a Morgan formatter function for ecs-logging output.
//
// @param {Object} opts - Optional.
//    - {String || Function} opts.format - A format *name* (e.g. 'combined'),
//      format function (e.g. `morgan.combined`), or a format string
//      (e.g. ':method :url :status'). This is used to format the "message"
//      field. Defaults to `morgan.combined`.
//    - {Boolean} opts.apmIntegration - Whether to automatically integrate with
//      Elastic APM (https://github.com/elastic/apm-agent-nodejs). If a started
//      APM agent is detected, then log records will include the following
//      fields:
//        - "service.name" - the configured serviceName in the agent
//        - "event.dataset" - set to "$serviceName" for correlation in Kibana
//        - "trace.id", "transaction.id", and "span.id" - if there is a current
//          active trace when the log call is made
//      Default true.
//    - {String} serviceName - override `service.name` field from APM agent
//    - {String} serviceVersion - override `service.version` field from APM agent
//    - {String} serviceEnvironment - override `service.environment` field from APM agent
//    - {String} serviceNodeName - override `service.name` field from APM agent
//    - {String} eventDataset - override `event.dataset` field
//
// For backwards compatibility, the first argument can be a String or Function
// to specify `opts.format`. For example, the following are equivalent:
//    ecsFormat({format: 'combined'})
//    ecsFormat('combined')
// The former allows specifying other options.
function ecsFormat (opts) {
  let format = morgan.combined
  let apmIntegration = true
  if (opts && typeof opts === 'object') {
    // Usage: ecsFormat({ /* opts */ })
    if (opts.format != null) {
      format = opts.format
    }
    if (opts.apmIntegration != null) {
      apmIntegration = opts.apmIntegration
    }
  } else if (opts) {
    // Usage: ecsFormat(format)
    format = opts
    opts = {}
  } else {
    // Usage: ecsFormat()
    opts = {}
  }

  // Resolve to a format function a la morgan's own `getFormatFunction`.
  let fmt = morgan[format] || format
  if (typeof fmt !== 'function') {
    fmt = morgan.compile(fmt)
  }

  let apm = null
  if (apmIntegration && elasticApm && elasticApm.isStarted && elasticApm.isStarted()) {
    apm = elasticApm
  }

  const extraFields = {}

  // Set a number of correlation fields from (a) the given options or (b) an
  // APM agent, if there is one running.
  let serviceName = opts.serviceName
  if (serviceName == null && apm) {
    // istanbul ignore next
    serviceName = (apm.getServiceName
      ? apm.getServiceName() // added in elastic-apm-node@3.11.0
      : apm._conf.serviceName) // fallback to private `_conf`
  }
  if (serviceName) {
    extraFields['service.name'] = serviceName
  }

  let serviceVersion = opts.serviceVersion
  // istanbul ignore next
  if (serviceVersion == null && apm) {
    serviceVersion = (apm.getServiceVersion
      ? apm.getServiceVersion() // added in elastic-apm-node@...
      : apm._conf.serviceVersion) // fallback to private `_conf`
  }
  if (serviceVersion) {
    extraFields['service.version'] = serviceVersion
  }

  let serviceEnvironment = opts.serviceEnvironment
  if (serviceEnvironment == null && apm) {
    // istanbul ignore next
    serviceEnvironment = (apm.getServiceEnvironment
      ? apm.getServiceEnvironment() // added in elastic-apm-node@...
      : apm._conf.environment) // fallback to private `_conf`
  }
  if (serviceEnvironment) {
    extraFields['service.environment'] = serviceEnvironment
  }

  let serviceNodeName = opts.serviceNodeName
  if (serviceNodeName == null && apm) {
    // istanbul ignore next
    serviceNodeName = (apm.getServiceNodeName
      ? apm.getServiceNodeName() // added in elastic-apm-node@...
      : apm._conf.serviceNodeName) // fallback to private `_conf`
  }
  if (serviceNodeName) {
    extraFields['service.node.name'] = serviceNodeName
  }

  let eventDataset = opts.eventDataset
  if (eventDataset == null && serviceName) {
    eventDataset = serviceName
  }
  if (eventDataset) {
    extraFields['event.dataset'] = eventDataset
  }

  return function formatter (token, req, res) {
    const ecsFields = {
      '@timestamp': new Date().toISOString(),
      'log.level': res.statusCode < 500 ? 'info' : 'error',
      message: fmt(token, req, res),
      'ecs.version': version,
      ...extraFields
    }

    // https://www.elastic.co/guide/en/ecs/current/ecs-tracing.html
    if (apm) {
      const tx = apm.currentTransaction
      // istanbul ignore else
      if (tx) {
        ecsFields['trace.id'] = tx.traceId
        ecsFields['transaction.id'] = tx.id
        // Not including `span.id` because the way morgan logs (on the HTTP
        // Response "finished" event), any spans during the request handler
        // are no longer active.
      }
    }

    // https://www.elastic.co/guide/en/ecs/current/ecs-http.html
    formatHttpRequest(ecsFields, req)
    formatHttpResponse(ecsFields, res)

    return stringify(ecsFields)
  }
}

// For backwards compatibility with v1.0.0, the top-level export is `ecsFormat`,
// though using the named export is preferred.
module.exports = ecsFormat
module.exports.ecsFormat = ecsFormat
module.exports.default = ecsFormat