resource/aws_subnet: Handle read-after-create eventual consistency

Reference: #12829
Reference: #16796

Output from acceptance testing in AWS Commercial:

```
--- PASS: TestAccAWSSubnet_availabilityZoneId (53.74s)
--- PASS: TestAccAWSSubnet_basic (52.50s)
--- PASS: TestAccAWSSubnet_defaultAndIgnoreTags (80.26s)
--- PASS: TestAccAWSSubnet_defaultTags_providerAndResource_duplicateTag (6.45s)
--- PASS: TestAccAWSSubnet_defaultTags_providerAndResource_nonOverlappingTag (84.84s)
--- PASS: TestAccAWSSubnet_defaultTags_providerAndResource_overlappingTag (86.61s)
--- PASS: TestAccAWSSubnet_defaultTags_providerOnly (87.99s)
--- PASS: TestAccAWSSubnet_defaultTags_updateToProviderOnly (69.48s)
--- PASS: TestAccAWSSubnet_defaultTags_updateToResourceOnly (72.12s)
--- PASS: TestAccAWSSubnet_disappears (41.08s)
--- PASS: TestAccAWSSubnet_enableIpv6 (109.36s)
--- PASS: TestAccAWSSubnet_ignoreTags (81.13s)
--- PASS: TestAccAWSSubnet_ipv6 (118.69s)
--- PASS: TestAccAWSSubnet_MapPublicIpOnLaunch (118.55s)
--- PASS: TestAccAWSSubnet_tags (106.25s)
--- SKIP: TestAccAWSSubnet_CustomerOwnedIpv4Pool (1.44s)
--- SKIP: TestAccAWSSubnet_MapCustomerOwnedIpOnLaunch (1.40s)
--- SKIP: TestAccAWSSubnet_outpost (1.70s)
```

Output from acceptance testing in AWS GovCloud (US):

```
--- PASS: TestAccAWSSubnet_availabilityZoneId (55.41s)
--- PASS: TestAccAWSSubnet_basic (55.46s)
--- PASS: TestAccAWSSubnet_defaultAndIgnoreTags (85.95s)
--- PASS: TestAccAWSSubnet_defaultTags_providerAndResource_duplicateTag (6.64s)
--- PASS: TestAccAWSSubnet_defaultTags_providerAndResource_nonOverlappingTag (82.23s)
--- PASS: TestAccAWSSubnet_defaultTags_providerAndResource_overlappingTag (84.95s)
--- PASS: TestAccAWSSubnet_defaultTags_providerOnly (86.26s)
--- PASS: TestAccAWSSubnet_defaultTags_updateToProviderOnly (69.05s)
--- PASS: TestAccAWSSubnet_defaultTags_updateToResourceOnly (73.74s)
--- PASS: TestAccAWSSubnet_disappears (42.78s)
--- PASS: TestAccAWSSubnet_enableIpv6 (117.40s)
--- PASS: TestAccAWSSubnet_ignoreTags (83.74s)
--- PASS: TestAccAWSSubnet_ipv6 (126.25s)
--- PASS: TestAccAWSSubnet_MapPublicIpOnLaunch (124.27s)
--- PASS: TestAccAWSSubnet_tags (115.31s)
--- SKIP: TestAccAWSSubnet_CustomerOwnedIpv4Pool (6.95s)
--- SKIP: TestAccAWSSubnet_MapCustomerOwnedIpOnLaunch (2.60s)
--- SKIP: TestAccAWSSubnet_outpost (2.14s)
```

.changelog/pending.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+resource/aws_subnet: Handle EC2 eventual consistency errors on creation
+```

aws/internal/service/ec2/waiter/waiter.go

@@ -270,6 +270,7 @@ func SecurityGroupCreated(conn *ec2.EC2, id string, timeout time.Duration) (*ec2
 }
 
 const (
+	SubnetPropagationTimeout          = 2 * time.Minute
 	SubnetAttributePropagationTimeout = 5 * time.Minute
 )
 

aws/resource_aws_subnet.go

@@ -7,10 +7,13 @@ import (
 
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/service/ec2"
+	"github.com/hashicorp/aws-sdk-go-base/tfawserr"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/resource"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
 	"github.com/terraform-providers/terraform-provider-aws/aws/internal/keyvaluetags"
+	"github.com/terraform-providers/terraform-provider-aws/aws/internal/service/ec2/finder"
 	"github.com/terraform-providers/terraform-provider-aws/aws/internal/service/ec2/waiter"
+	"github.com/terraform-providers/terraform-provider-aws/aws/internal/tfresource"
 )
 
 func resourceAwsSubnet() *schema.Resource {
@@ -232,23 +235,53 @@ func resourceAwsSubnetRead(d *schema.ResourceData, meta interface{}) error {
 	defaultTagsConfig := meta.(*AWSClient).DefaultTagsConfig
 	ignoreTagsConfig := meta.(*AWSClient).IgnoreTagsConfig
 
-	resp, err := conn.DescribeSubnets(&ec2.DescribeSubnetsInput{
-		SubnetIds: []*string{aws.String(d.Id())},
-	})
+	var subnet *ec2.Subnet
 
-	if err != nil {
-		if isAWSErr(err, "InvalidSubnetID.NotFound", "") {
-			log.Printf("[WARN] Subnet (%s) not found, removing from state", d.Id())
-			d.SetId("")
-			return nil
+	err := resource.Retry(waiter.SubnetPropagationTimeout, func() *resource.RetryError {
+		var err error
+
+		subnet, err = finder.SubnetByID(conn, d.Id())
+
+		if d.IsNewResource() && tfawserr.ErrCodeEquals(err, "InvalidSubnetID.NotFound") {
+			return resource.RetryableError(err)
 		}
-		return err
+
+		if err != nil {
+			return resource.NonRetryableError(err)
+		}
+
+		if d.IsNewResource() && subnet == nil {
+			return resource.RetryableError(&resource.NotFoundError{
+				LastError: fmt.Errorf("EC2 Subnet (%s) not found", d.Id()),
+			})
+		}
+
+		return nil
+	})
+
+	if tfresource.TimedOut(err) {
+		subnet, err = finder.SubnetByID(conn, d.Id())
 	}
-	if resp == nil {
+
+	if !d.IsNewResource() && tfawserr.ErrCodeEquals(err, "InvalidSubnetID.NotFound") {
+		log.Printf("[WARN] EC2 Subnet (%s) not found, removing from state", d.Id())
+		d.SetId("")
 		return nil
 	}
 
-	subnet := resp.Subnets[0]
+	if err != nil {
+		return fmt.Errorf("error reading EC2 Subnet (%s): %w", d.Id(), err)
+	}
+
+	if subnet == nil {
+		if d.IsNewResource() {
+			return fmt.Errorf("error reading EC2 Subnet (%s): not found after creation", d.Id())
+		}
+
+		log.Printf("[WARN] EC2 Subnet (%s) not found, removing from state", d.Id())
+		d.SetId("")
+		return nil
+	}
 
 	d.Set("vpc_id", subnet.VpcId)
 	d.Set("availability_zone", subnet.AvailabilityZone)