Fix for #18

Author: tmitchel2

flow/aws-sdk-promise.js

@@ -467,6 +467,7 @@ declare module 'aws-sdk-promise' {
   declare type Datapoint = {
     Timestamp: string,
     Average: number,
+    Sum: number,
     Unit: string,
   };
 }

src/CapacityCalculator.js

@@ -15,12 +15,12 @@ export default class CapacityCalculator extends CapacityCalculatorBase {
     return {
       count: 5,
       spanMinutes: 1,
-      type: 'Average',
+      type: 'Sum',
     };
   }
 
   // Gets the projected capacity value based on the cloudwatch datapoints
-  getProjectedValue(data: GetMetricStatisticsResponse) {
+  getProjectedValue(settings: StatisticSettings, data: GetMetricStatisticsResponse) {
     invariant(data != null, 'Parameter \'data\' is not set');
 
     if (data.Datapoints.length === 0) {
@@ -30,7 +30,9 @@ export default class CapacityCalculator extends CapacityCalculatorBase {
     // Default algorithm for projecting a good value for the current ConsumedThroughput is:
     // 1. Query 5 average readings each spanning a minute
     // 2. Select the Max value from those 5 readings
-    let averages = data.Datapoints.map(dp => dp.Sum / data.period);
-    return Math.max(...averages);
+    let spanSeconds = settings.spanMinutes * 60;
+    let averages = data.Datapoints.map(dp => dp.Sum / spanSeconds);
+    let projectedValue = Math.max(...averages);
+    return projectedValue;
   }
 }

src/capacity/CapacityCalculatorBase.js

@@ -31,7 +31,7 @@ export default class CapacityCalculatorBase {
 
   // Gets the projected capacity value based on the cloudwatch datapoints
   // eslint-disable-next-line no-unused-vars
-  getProjectedValue(data: GetMetricStatisticsResponse): number {
+  getProjectedValue(settings: StatisticSettings, data: GetMetricStatisticsResponse): number {
     invariant(false, 'The method \'getProjectedValue\' was not implemented');
   }
 
@@ -100,31 +100,27 @@ export default class CapacityCalculatorBase {
       invariant(isRead != null, 'Parameter \'isRead\' is not set');
       invariant(tableName != null, 'Parameter \'tableName\' is not set');
 
-      // These values determine how many minutes worth of metrics
-      let statisticCount = 5;
-      let statisticSpanMinutes = 1;
-      let statisticType = 'Sum';
+      let settings = this.getStatisticSettings();
 
       let EndTime = new Date();
       let StartTime = new Date();
-      StartTime.setTime(EndTime - (60000 * statisticSpanMinutes * statisticCount));
+      StartTime.setTime(EndTime - (60000 * settings.spanMinutes * settings.count));
       let MetricName = isRead ? 'ConsumedReadCapacityUnits' : 'ConsumedWriteCapacityUnits';
       let Dimensions = this.getDimensions(tableName, globalSecondaryIndexName);
-      let period = (statisticSpanMinutes * 60);
+      let period = (settings.spanMinutes * 60);
       let params = {
         Namespace: 'AWS/DynamoDB',
         MetricName,
         Dimensions,
         StartTime,
         EndTime,
         Period: period,
-        Statistics: [ statisticType ],
+        Statistics: [ settings.type ],
         Unit: 'Count'
       };
 
       let statistics = await this.cw.getMetricStatisticsAsync(params);
-      statistics.period = period;
-      let value = this.getProjectedValue(statistics);
+      let value = this.getProjectedValue(settings, statistics);
       let result: ConsumedCapacityDesc = {
         tableName,
         globalSecondaryIndexName,