public virtual async Task Failover()

in static/Reliability/300_Testing_for_Resiliency_of_EC2_RDS_and_S3/Code/FailureSimulations/c#/AppResiliency/AppResiliency/AZFailover.cs [55:133]
60 lines of code
8 McCabe index (conditional complexity)

        public virtual async Task Failover()
        {
            try
            {
                Console.WriteLine($"Simulating AZ failure for {azName}");

                // Find all subnets in the availability zone passed in the input
                DescribeSubnetsResponse subnetsInSpecifiedAZandVpc
                        = await ec2Client.DescribeSubnetsAsync(new DescribeSubnetsRequest()
                        {
                            Filters = new List<Amazon.EC2.Model.Filter> {
                                    new Amazon.EC2.Model.Filter {
                                        Name = "vpc-id",
                                        Values = { vpcId }
                                    },
                                    new Amazon.EC2.Model.Filter {
                                        Name = "availability-zone",
                                        Values = { azName }
                                    }
                            }
                        });

                List<string> subnetIdsInSpecifiedAZ = subnetsInSpecifiedAZandVpc.Subnets.Select(x => x.SubnetId).ToList();

                // Modify the autoscaling group to remove the AZ affected which is the AZ passed in the input
                // Find the autoscaling group that this is deployed into
                DescribeAutoScalingGroupsResponse autoScalingGroupsResponse = await asClient.DescribeAutoScalingGroupsAsync();

                if (autoScalingGroupsResponse != null && autoScalingGroupsResponse.AutoScalingGroups.Count > 0)
                {
                    // Note: This assumes an Auto Scaling group exists; no error checking for readability
                    AutoScalingGroup autoScalingGroup = autoScalingGroupsResponse.AutoScalingGroups[0];

                    Console.WriteLine($"Updating the auto scaling group {autoScalingGroup.AutoScalingGroupName} to remove the subnet in {azName}");

                    UpdateAutoScalingGroupResponse updateAutoScalingGroupResponse
                        = await asClient.UpdateAutoScalingGroupAsync(new UpdateAutoScalingGroupRequest
                        {
                            AutoScalingGroupName = autoScalingGroup.AutoScalingGroupName,
                            VPCZoneIdentifier = String.Join(",", autoScalingGroup.VPCZoneIdentifier.Split(',').Where(x => !subnetIdsInSpecifiedAZ.Contains(x)))
                        });
                }

                Console.WriteLine("Creating new network ACL associations");
                await BlockSubnetsInAZ(vpcId, subnetIdsInSpecifiedAZ);

                Console.WriteLine("Failing over database");

                //fail over rds which is in the same AZ
                DescribeDBInstancesResponse describeDBInstancesResult = await rdsClient.DescribeDBInstancesAsync();

                string dbInstancedId = describeDBInstancesResult.DBInstances.Where(x => String.Equals(x.DBSubnetGroup.VpcId, vpcId, StringComparison.OrdinalIgnoreCase) &&
                    String.Equals(x.AvailabilityZone, azName, StringComparison.OrdinalIgnoreCase) &&
                    x.MultiAZ &&
                    !x.StatusInfos.Any())?.Select(x => x.DBInstanceIdentifier).FirstOrDefault();

                // we want to fail over rds if rds is present in the same az where it is affected
                if (!String.IsNullOrEmpty(dbInstancedId))
                {
                    Console.WriteLine("Rebooting dbInstanceId to secondary AZ " + dbInstancedId);

                    var response = await rdsClient.RebootDBInstanceAsync(new RebootDBInstanceRequest()
                    {
                        DBInstanceIdentifier = dbInstancedId,
                        ForceFailover = true
                    });
                }
                else
                {
                    Console.WriteLine($"Didn't find DB in the same AZ as {azName}");
                }

                Console.Write("Done");
            }
            catch (Exception exception)
            {
                Console.WriteLine("Unknown exception occurred " + exception.Message);
            }
        }