exports.handler = function()

in nodejs/app.js [35:118]
52 lines of code
9 McCabe index (conditional complexity)

exports.handler = function (input, context, callback) {

  // API metrics array.
  let apiMetrics = {};

  // decode input from base64
  const zippedInput = new Buffer(input.awslogs.data, 'base64');

  // decompress the input
  zlib.gunzip(zippedInput, function (err, buffer) {

    if (err) { callback(err); }

    // Parse JSON from input.

    const awslogsData = JSON.parse(buffer.toString('utf8'));

    if (awslogsData.messageType === 'CONTROL_MESSAGE') {
      callback(null, "Successfully posted control message!");
    }

    // Populate metrics params array from log events.

    console.log(awslogsData.logEvents.length + " events captured.");

    awslogsData.logEvents.forEach(function (logEvent, index, logEventsArr) {

      const event = JSON.parse(logEvent.message);

      const hash = [event.eventTime, event.eventName, event.awsRegion, event.eventSource];

      // Filling any undefined values to prevent errors on "PutMetricData" call.

      for (index in hash) {
        if (!hash[index]) { hash[index] = '-' }
      }

      if (apiMetrics[hash]) {
        apiMetrics[hash].Value++;
      } else {
        apiMetrics[hash] = {
          Timestamp: hash[0],
          MetricName: hash[1],
          Dimensions: [{
            Name: 'awsRegion',
            Value: hash[2]
          }, {
            Name: 'eventSource',
            Value: hash[3]
          }],
          Value: 1
        };
      }

    });

    let apiMetricParams = [];
    let promiseList = [];

    // Submit every 20 metric (BATCH size)

    for (const hash in apiMetrics) {
      apiMetricParams.push(apiMetrics[hash]);
      if (apiMetricParams.length == BATCH) {
        promiseList.push(postToCloudWatch(apiMetricParams));
        apiMetricParams = [];
      }
    }

    // Submit final set of metric

    if (apiMetricParams.length > 0) promiseList.push(postToCloudWatch(apiMetricParams));

    // Ensure all data posted before callback

    Promise.all(promiseList).then(function (val) {
      console.log("Successfully posted " + val + " events!");
      callback(null, "Successfully posted " + val + " events!");
    }).catch(function (err) {
      console.log('A promise failed to resolve', err);
      callback(err);
    });
  });
};