aws_cloudwatch_get_metrics.go

package main

// Note: I initially wrote this script to delete old Cloudwatch metrics
// but I found out too late that it's not possible to do delete metrics from CloudWatch
// so just keeping this script as a usage example of the metrics statistics manipulations

import (
  "github.com/aws/aws-sdk-go/aws"
  "github.com/aws/aws-sdk-go/aws/session"
  "github.com/aws/aws-sdk-go/service/cloudwatch"
  "github.com/aws/aws-sdk-go/service/cloudwatch/cloudwatchiface"

  "fmt"
  "time"
)

// CWProcessor is used to share the Cloudwatch client between functions
type CWProcessor struct {
  svc cloudwatchiface.CloudWatchAPI
}

// newCWProcessor initiates a new cloudwatch client
func newCWProcessor() *CWProcessor {
  sess := session.Must(session.NewSessionWithOptions(session.Options{
    SharedConfigState: session.SharedConfigEnable,
  }))
  return &CWProcessor{svc: cloudwatch.New(sess)}
}

// processMetrics pulls the list of metrics and check if the latest datapoint of
// each metric is older than the given number of days (must be within the last 2
// years if yes, prints the informations
func (c *CWProcessor) processMetrics(daysLimit int) {
  params := &cloudwatch.ListMetricsInput{}
  timeLimit := time.Now().AddDate(0, 0, -daysLimit)
  err := c.svc.ListMetricsPages(params,
    func(page *cloudwatch.ListMetricsOutput, lastPage bool) bool {
      for _, m := range page.Metrics {
        last := c.getLatestMetricUpdate(m)
        if last == nil || timeLimit.After(*last) {
          fmt.Printf("%s / %s %v: %s\n", *m.Namespace, *m.MetricName, m.Dimensions, last)
        }
      }
      return !lastPage
    })
  if err != nil {
    fmt.Println("Error", err)
    return
  }
}

// getLatestMetricUpdate returns the date of the latest datapoint in the given
// metric and nil if nothing was found over the last 3 months
func (c *CWProcessor) getLatestMetricUpdate(metric *cloudwatch.Metric) *time.Time {
  end := time.Now()
  start := end.AddDate(-2, 0, 0)
  period := int64(24 * 3600)
  params := cloudwatch.GetMetricStatisticsInput{
    Dimensions: metric.Dimensions,
    MetricName: metric.MetricName,
    Namespace:  metric.Namespace,
    StartTime:  &start,
    Period:     &period,
    EndTime:    &end,
    Statistics: []*string{aws.String("Sum")},
  }
  result, err := c.svc.GetMetricStatistics(&params)
  if err != nil {
    fmt.Println(err)
  }
  latest := c.getLatestDatapoint(result.Datapoints)
  return latest.Timestamp
}

// getLatestDatapoint returns the latest datapoint (timewise) found in an array of datapoints
func (c *CWProcessor) getLatestDatapoint(dps []*cloudwatch.Datapoint) *cloudwatch.Datapoint {
  var latest *cloudwatch.Datapoint
  for _, dp := range dps {
    if latest == nil {
      latest = dp
    } else {
      if latest.Timestamp != nil && (*dp.Timestamp).After(*latest.Timestamp) {
        latest = dp
      }
    }
  }
  return latest
}

func main() {
  p := newCWProcessor()
  p.processMetrics(30)
}