Add comments about updating payload calculations with entity data (#1483

)

.golangci.yml

@@ -19,7 +19,7 @@ run:
 
 output:
   # colored-line-number|line-number|json|tab|checkstyle|code-climate, default is "colored-line-number"
-  format: colored-line-number
+  formats: colored-line-number
 
   # print lines of code with issue, default is true
   print-issued-lines: true

plugins/outputs/cloudwatch/cloudwatch.go

@@ -174,6 +174,19 @@ func (c *CloudWatch) pushMetricDatum() {
 		case metric := <-c.metricChan:
 			entity, datums := c.BuildMetricDatum(metric)
 			numberOfPartitions := len(datums)
+			/* We currently do not account for entity information as a part of the payload size.
+			This is by design and should be revisited once the SDK protocol changes.
+			In the meantime there has been a payload limit increase applied in the background to accommodate this decision
+
+			Otherwise to include entity size you would do something like this:
+			c.metricDatumBatch.Size += calculateEntitySize(entity)
+
+			In addition to calculating the size of the entity object, you might also need to account for any extra bytes that get
+			added on an individual metric level when entity data is present (depends on how the sdk protocol changes)—something like:
+			c.metricDatumBatch.Size += payload(datums[i], entityPresent=true)
+
+			File diff that could be useful: https://github.com/aws/amazon-cloudwatch-agent/compare/af960d7...459ef7c
+			*/
 			for i := 0; i < numberOfPartitions; i++ {
 				entityStr := entityToString(entity)
 				c.metricDatumBatch.Partition[entityStr] = append(c.metricDatumBatch.Partition[entityStr], datums[i])

plugins/outputs/cloudwatch/util.go

@@ -46,6 +46,19 @@ const (
 	valueOverheads = 47
 	// &MetricData.member.1.Unit=Kilobytes/Second
 	unitOverheads = 42
+
+	/* Entity overheads - these would be used to calculate entity size if we decide to include it as a part of the payload.
+	The three main components are the KeyAttributes key/value pair, Attributes key/value pair, and StrictEntityValidation
+
+	// &StrictEntityValidation=false
+	strictEntityValidationSize = 29
+	// &EntityMetricData.member.100.Entity.KeyAttributes.entry.1.key= &EntityMetricData.member.100.Entity.KeyAttributes.entry.1.value=
+	entityKeyAttributesOverhead = 62 + 64
+	// &EntityMetricData.member.100.Entity.Attributes.entry.1.key= &EntityMetricData.member.100.Entity.Attributes.entry.1.value=
+	entityAttributesOverhead = 59 + 61
+	// EntityMetricData.member.100.
+	entityMetricDataPrefixOverhead = 28
+	*/
 )
 
 // Set seed once.