具有云形成和AZ问题的RDS [英] RDS with Cloud Formation and AZ issues

问题描述

我正在使用云形成来创建包含RDS实例的设置。

I am using cloud formation to create a setup containing an RDS instance.

由于以下错误，我在创建RDS实例时遇到了一些困难：

I am having some difficulties creating the RDS Instance on the account of the following error:

DB子网组不满足可用性区域覆盖范围的要求。
请添加子网以覆盖至少2个可用区。当前的
覆盖率：1

DB Subnet Group doesn't meet availability zone coverage requirement. Please add subnets to cover at least 2 availability zones. Current coverage: 1

问题是整个设置位于单个AZ上...我该怎么办去做？只是在另一个仅用于RDS的可用区中创建一个额外的子网？

The problem is that the entire setup is on a single AZ... what am i supposed to do? just create an extra subnet in a different AZ that has nothing in it just for the RDS?

也许AWS可以通过某种方式自动创建该子网并将我拒之门外那一团糟。我不需要额外的子网，也不想为此选择另一个可用区负担。

Maybe there is some way AWS can create that subnet automatically and leave me out of that mess. I don't want that extra subnet and I don't want to burden my users with selecting another AZ just for this.

推荐答案

是的，即使对于完全包含在单个可用区[AZ]中的部署，也必须在不同的AZ中创建一个额外的子网，并将其包含在DB子网组中。此要求的基本原理是支持高可用性多可用区部署，如在RDS用户指南的VPC中使用数据库实例部分：

Yes, even for a deployment entirely contained within a single Availability Zone [AZ], you must create an extra subnet in a different AZ and include it in your DB Subnet Group. The rationale for this requirement is to support high-availability Multi-AZ deployments, as noted in the Working with a DB Instance in a VPC section of the RDS User Guide:

对于多可用区部署，为一个区域中的两个或多个可用区定义一个子网允许Amazon RDS在需要时在另一个可用区中创建新的备用站点。即使在单可用区部署中，您也需要这样做，以防万一您想将它们转换为多可用区部署。

For Multi-AZ deployments, defining a subnet for two or more Availability Zones in a region allows Amazon RDS to create a new standby in another Availability Zone should the need arise. You need to do this even for Single-AZ deployments, just in case you want to convert them to Multi-AZ deployments at some point.

<对于不为此而选择另一个可用区，不会给用户带来负担，有多种方法可以实现。例如，您可以使用 Fn :: GetAZs 和 Fn :: Select 内在函数。如果您允许用户选择主要可用区，则还需要条件，以确保辅助可用区与所选的主要可用区不相等。

As for not burdening your users with selecting another AZ just for this, there are ways to accomplish this. For example, you could select a secondary AZ automatically using the Fn::GetAZs and Fn::Select intrinsic functions. If you allow the user to select the primary AZ, you'll also need a Condition to ensure the secondary AZ doesn't equal the primary AZ selected.

以下是示例模板摘要：

Parameters:
  PrimaryAZ:
    Type: AWS::EC2::AvailabilityZone::Name
    Description: Primary AZ
Conditions:
  IsFirstPrimaryAZ:
    Fn::Equals:
    - !Ref PrimaryAZ
    - Fn::Select [0, {Fn::GetAZs: ""}]
Resources:
  Subnet1:
    Type: "AWS::EC2::Subnet"
    Properties:
      AvailabilityZone: !Ref PrimaryAZ
      # ...
  Subnet2:
    Type: "AWS::EC2::Subnet"
    Properties:
      AvailabilityZone:
        Fn::If:
        - IsFirstPrimaryAZ
        - Fn::Select [1, {Fn::GetAZs: ""}]
        - Fn::Select [0, {Fn::GetAZs: ""}]
      # ...

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