index.js

const CorrelationIds = require('@dazn/lambda-powertools-correlation-ids')
const HTTP = require('superagent-promise')(require('superagent'), Promise)
const Metrics = require('@dazn/datadog-metrics')
const URL = require('url')

const AWS_REGION = process.env.AWS_REGION || process.env.AWS_DEFAULT_REGION
const FUNCTION_NAME = process.env.AWS_LAMBDA_FUNCTION_NAME
const FUNCTION_VERSION = process.env.AWS_LAMBDA_FUNCTION_VERSION

const DEFAULT_TAGS = [
  `awsRegion:${AWS_REGION}`,
  `functionName:${FUNCTION_NAME}`,
  `functionVersion:${FUNCTION_VERSION}`
]

function getRequest (uri, method) {
  switch (method.toLowerCase()) {
    case '':
    case 'get':
      return HTTP.get(uri)
    case 'head':
      return HTTP.head(uri)
    case 'post':
      return HTTP.post(uri)
    case 'put':
      return HTTP.put(uri)
    case 'delete':
      return HTTP.del(uri)
    default:
      throw new Error(`unsupported method : ${method.toLowerCase()}`)
  }
}

function setHeaders (request, headers) {
  const headerNames = Object.keys(headers)
  headerNames.forEach(h => {
    const headerValue = headers[h]
    if (headerValue !== null && headerValue !== undefined) {
      request = request.set(h, headerValue)
    }
  })

  return request
}

function setQueryStrings (request, qs) {
  if (!qs) {
    return request
  }

  return request.query(qs)
}

function setBody (request, body) {
  if (!body) {
    return request
  }

  return request.send(body)
}

// options: {
//    uri     : string
//    method  : GET (default) | POST | PUT | HEAD
//    headers : object
//    qs      : object
//    body    : object
//    metricName [optional] : string  (e.g. adyenApi)
//    metricTags [optional] : string []  (e.g. ['request_type:submit', 'load_test'], by default we add function name, version, HTTP method, path, and response statusCode for you as tags)
//    timeout [optional] : int (ms)
//    correlationIds : CorrelationIds (an instance of @dazn/lambda-powertools-correlation-ids class)
//  }
const Req = (options) => {
  if (!options) {
    throw new Error('no HTTP request options is provided')
  }

  if (!options.uri) {
    throw new Error('no HTTP uri is specified')
  }

  const correlationIds = (options.correlationIds || CorrelationIds).get()

  // copy the provided headers last so it overrides the values from the context
  let headers = Object.assign({}, correlationIds, options.headers)

  const method = options.method || 'get'
  let request = getRequest(options.uri, method)

  request = setHeaders(request, headers)
  request = setQueryStrings(request, options.qs)
  request = setBody(request, options.body)

  if (options.timeout && typeof options.timeout === 'number') {
    request = request.timeout({ deadline: options.timeout })
  }

  const start = Date.now()
  const url = new URL.URL(options.uri)
  const metricName = options.methicName || url.hostname + '.response'
  const requestMetricTags = [
    `method:${method}`,
    `path:${url.pathname}`
  ]
  let metricTags = [].concat(DEFAULT_TAGS, requestMetricTags, options.metricTags || [])

  const recordMetrics = ({ status }) => {
    const end = Date.now()
    const latency = end - start

    metricTags.push(`statusCode:${status}`)

    Metrics.histogram(`${metricName}.latency`, latency, metricTags)
    Metrics.increment(`${metricName}.${status}`, 1, metricTags)
  }

  return request
    .then(resp => {
      recordMetrics(resp)
      return resp
    })
    .catch(e => {
      if (e.response) {
        recordMetrics(e.response)

        if (e.response.error) {
          throw e.response.error
        }
      }

      throw e
    })
}

module.exports = Req