feat(metric): Add rds_instance_age_seconds representing age of the in…

…stance

README.md

@@ -48,6 +48,7 @@ It collect key metrics about:
 | rds_exporter_errors_total | | Total number of errors encountered by the exporter |
 | rds_free_storage_bytes | `aws_account_id`, `aws_region`, `dbidentifier` | Free storage on the instance |
 | rds_freeable_memory_bytes | `aws_account_id`, `aws_region`, `dbidentifier` | Amount of available random access memory. For MariaDB, MySQL, Oracle, and PostgreSQL DB instances, this metric reports the value of the MemAvailable field of /proc/meminfo |
+| rds_instance_age_seconds | `aws_account_id`, `aws_region`, `dbidentifier` | Instance age |
 | rds_instance_info | `aws_account_id`, `aws_region`, `dbi_resource_id`, `dbidentifier`, `deletion_protection`, `engine`, `engine_version`, `instance_class`, `multi_az`, `performance_insights_enabled`, `pending_maintenance`, `pending_modified_values`, `role`, `source_dbidentifier`, `storage_type` | RDS instance information |
 | rds_instance_log_files_size_bytes | `aws_account_id`, `aws_region`, `dbidentifier` | Total of log files on the instance |
 | rds_instance_max_iops_average | `aws_account_id`, `aws_region`, `dbidentifier` | Maximum IOPS of underlying EC2 instance |
@@ -64,10 +65,10 @@ It collect key metrics about:
 | rds_quota_total_storage_bytes | `aws_account_id`, `aws_region` | Maximum total storage for all DB instances |
 | rds_read_iops_average | `aws_account_id`, `aws_region`, `dbidentifier` | Average number of disk read I/O operations per second |
 | rds_read_throughput_bytes | `aws_account_id`, `aws_region`, `dbidentifier` | Average number of bytes read from disk per second |
-| rds_transaction_logs_disk_usage_bytes | `aws_account_id`, `aws_region`, `dbidentifier` | Disk space used by transaction logs (only on PostgreSQL) |
 | rds_replica_lag_seconds | `aws_account_id`, `aws_region`, `dbidentifier` | For read replica configurations, the amount of time a read replica DB instance lags behind the source DB instance. Applies to MariaDB, Microsoft SQL Server, MySQL, Oracle, and PostgreSQL read replicas |
 | rds_replication_slot_disk_usage_average | `aws_account_id`, `aws_region`, `dbidentifier` | Disk space used by replication slot files. Applies to PostgreSQL |
 | rds_swap_usage_bytes | `aws_account_id`, `aws_region`, `dbidentifier` | Amount of swap space used on the DB instance. This metric is not available for SQL Server |
+| rds_transaction_logs_disk_usage_bytes | `aws_account_id`, `aws_region`, `dbidentifier` | Disk space used by transaction logs (only on PostgreSQL) |
 | rds_usage_allocated_storage_average | `aws_account_id`, `aws_region` | Total storage used by AWS RDS instances |
 | rds_usage_db_instances_average | `aws_account_id`, `aws_region` | AWS RDS instance count |
 | rds_usage_manual_snapshots_average | `aws_account_id`, `aws_region` | Manual snapshots count |

internal/app/exporter/exporter.go

@@ -99,6 +99,7 @@ type rdsCollector struct {
 	exporterBuildInformation    *prometheus.Desc
 	transactionLogsDiskUsage    *prometheus.Desc
 	certificateValidTill        *prometheus.Desc
+	age                         *prometheus.Desc
 }
 
 func NewCollector(logger slog.Logger, collectorConfiguration Configuration, awsAccountID string, awsRegion string, rdsClient rdsClient, ec2Client EC2Client, cloudWatchClient cloudWatchClient, servicequotasClient servicequotasClient) *rdsCollector {
@@ -129,6 +130,10 @@ func NewCollector(logger slog.Logger, collectorConfiguration Configuration, awsA
 			"RDS instance information",
 			[]string{"aws_account_id", "aws_region", "dbidentifier", "dbi_resource_id", "instance_class", "engine", "engine_version", "storage_type", "multi_az", "deletion_protection", "role", "source_dbidentifier", "pending_modified_values", "pending_maintenance", "performance_insights_enabled", "ca_certificate_identifier"}, nil,
 		),
+		age: prometheus.NewDesc("rds_instance_age_seconds",
+			"RDS age",
+			[]string{"aws_account_id", "aws_region", "dbidentifier"}, nil,
+		),
 		maxAllocatedStorage: prometheus.NewDesc("rds_max_allocated_storage_bytes",
 			"Upper limit in gibibytes to which Amazon RDS can automatically scale the storage of the DB instance",
 			[]string{"aws_account_id", "aws_region", "dbidentifier"}, nil,
@@ -454,6 +459,10 @@ func (c *rdsCollector) Collect(ch chan<- prometheus.Metric) {
 		ch <- prometheus.MustNewConstMetric(c.backupRetentionPeriod, prometheus.GaugeValue, float64(instance.BackupRetentionPeriod), c.awsAccountID, c.awsRegion, dbidentifier)
 		ch <- prometheus.MustNewConstMetric(c.certificateValidTill, prometheus.GaugeValue, float64(instance.CertificateValidTill.Unix()), c.awsAccountID, c.awsRegion, dbidentifier)
 
+		if instance.Age != nil {
+			ch <- prometheus.MustNewConstMetric(c.age, prometheus.GaugeValue, *instance.Age, c.awsAccountID, c.awsRegion, dbidentifier)
+		}
+
 		if instance.LogFilesSize != nil {
 			ch <- prometheus.MustNewConstMetric(c.logFilesSize, prometheus.GaugeValue, float64(*instance.LogFilesSize), c.awsAccountID, c.awsRegion, dbidentifier)
 		}

internal/app/rds/rds.go

@@ -51,6 +51,7 @@ type RdsInstanceMetrics struct {
 	SourceDBInstanceIdentifier       string
 	CACertificateIdentifier          string
 	CertificateValidTill             time.Time
+	Age                              *float64
 }
 
 const (
@@ -254,6 +255,13 @@ func (r *RDSFetcher) computeInstanceMetrics(dbInstance aws_rds_types.DBInstance,
 
 	role, sourceDBInstanceIdentifier := getRoleInCluster(&dbInstance)
 
+	var age *float64
+
+	if dbInstance.InstanceCreateTime != nil {
+		diff := time.Since(*dbInstance.InstanceCreateTime).Seconds()
+		age = &diff
+	}
+
 	metrics := RdsInstanceMetrics{
 		AllocatedStorage:           converter.GigaBytesToBytes(dbInstance.AllocatedStorage),
 		BackupRetentionPeriod:      converter.DaystoSeconds(dbInstance.BackupRetentionPeriod),
@@ -277,6 +285,7 @@ func (r *RDSFetcher) computeInstanceMetrics(dbInstance aws_rds_types.DBInstance,
 		StorageType:                *dbInstance.StorageType,
 		CACertificateIdentifier:    *dbInstance.CACertificateIdentifier,
 		CertificateValidTill:       *dbInstance.CertificateDetails.ValidTill,
+		Age:                        age,
 	}
 
 	return metrics, nil

internal/app/rds/rds_test.go

@@ -68,6 +68,7 @@ func newRdsCertificateDetails() *aws_rds_types.CertificateDetails {
 
 func newRdsInstance() *aws_rds_types.DBInstance {
 	DBInstanceIdentifier := randomString(10)
+	now := time.Now()
 
 	return &aws_rds_types.DBInstance{
 		AllocatedStorage:           5,
@@ -88,6 +89,7 @@ func newRdsInstance() *aws_rds_types.DBInstance {
 		StorageType:                aws.String("gp3"),
 		CACertificateIdentifier:    aws.String("rds-ca-2019"),
 		CertificateDetails:         newRdsCertificateDetails(),
+		InstanceCreateTime:         &now,
 	}
 }
 
@@ -353,3 +355,21 @@ func TestPendingModificationDueToUnappliedParameterGroup(t *testing.T) {
 	require.NoError(t, err, "GetInstancesMetrics must succeed")
 	assert.Equal(t, true, metrics.Instances[*rdsInstance.DBInstanceIdentifier].PendingModifiedValues, "Should have pending modification")
 }
+
+func TestInstanceAge(t *testing.T) {
+	// Mock RDS instance
+	rdsInstance := newRdsInstance()
+	creationDate := time.Date(2023, 9, 25, 12, 25, 0, 0, time.UTC) // Date of our first release
+	rdsInstance.InstanceCreateTime = &creationDate
+	mockDescribeDBInstancesOutput := &aws_rds.DescribeDBInstancesOutput{DBInstances: []aws_rds_types.DBInstance{*rdsInstance}}
+
+	mock := mockRDSClient{DescribeDBInstancesOutput: mockDescribeDBInstancesOutput}
+	configuration := rds.Configuration{}
+	client := rds.NewFetcher(mock, configuration)
+	metrics, err := client.GetInstancesMetrics()
+
+	expectedAge := time.Since(*rdsInstance.InstanceCreateTime)
+
+	require.NoError(t, err, "GetInstancesMetrics must succeed")
+	assert.Equal(t, int(expectedAge.Seconds()), int(*metrics.Instances[*rdsInstance.DBInstanceIdentifier].Age), "Age should match expected age")
+}