Incorporate feedback

Signed-off-by: George Brighton <george@gebn.co.uk>

discovery/aws/ec2.go

@@ -228,8 +228,8 @@ func (d *EC2Discovery) refresh(ctx context.Context) ([]*targetgroup.Group, error
 	// Prometheus requires a reload if AWS adds a new AZ to the region.
 	if d.azToAZID == nil {
 		if err := d.refreshAZIDs(ctx); err != nil {
-			level.Warn(d.logger).Log(
-				"msg", "Unable to describe availability zones, ensure Prometheus has ec2:DescribeAvailabilityZones",
+			level.Debug(d.logger).Log(
+				"msg", "Unable to describe availability zones",
 				"err", err)
 		}
 	}
@@ -270,7 +270,7 @@ func (d *EC2Discovery) refresh(ctx context.Context) ([]*targetgroup.Group, error
 				azID, ok := d.azToAZID[*inst.Placement.AvailabilityZone]
 				if !ok && d.azToAZID != nil {
 					level.Debug(d.logger).Log(
-						"msg", "Availability zone not found, try reloading Prometheus",
+						"msg", "Availability zone not found",
 						"az", *inst.Placement.AvailabilityZone)
 				}
 				labels[ec2LabelAZID] = model.LabelValue(azID)

docs/configuration/configuration.md

@@ -898,7 +898,7 @@ The following meta labels are available on targets during [relabeling](#relabel_
 * `__meta_ec2_ami`: the EC2 Amazon Machine Image
 * `__meta_ec2_architecture`: the architecture of the instance
 * `__meta_ec2_availability_zone`: the availability zone in which the instance is running
-* `__meta_ec2_availability_zone_id`: the [availability zone ID](https://docs.aws.amazon.com/ram/latest/userguide/working-with-az-ids.html) in which the instance is running
+* `__meta_ec2_availability_zone_id`: the [availability zone ID](https://docs.aws.amazon.com/ram/latest/userguide/working-with-az-ids.html) in which the instance is running (requires `ec2:DescribeAvailabilityZones`)
 * `__meta_ec2_instance_id`: the EC2 instance ID
 * `__meta_ec2_instance_lifecycle`: the lifecycle of the EC2 instance, set only for 'spot' or 'scheduled' instances, absent otherwise
 * `__meta_ec2_instance_state`: the state of the EC2 instance