如何使用 Cloud Formation 模板自动扩展 DynamoDB？

Question

创建 DynamoDB CloudFormation 模板时，需要指定 ProvisionedThroughput：

http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-dynamodb-table.html#cfn-dynamodb-table-provisionedthroughput

但我也看到这个文档说，当您通过控制台创建表时，默认情况下会设置 Auto Scaling。

http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/HowItWorks.ProvisionedThroughput.html#HowItWorks.ProvisionedThroughput.AutoScaling

我的问题是：为了让我的 DynamoDB 表自动缩放，我需要对 Cloudformation 做些什么特别的事情吗？

Answer 1

尚无法使用 CloudFormation 配置 Auto Scaling DynamoDB。

---

CloudFormation 不立即支持 AWS 服务的新功能是很常见的。添加支持的时间延迟可能会有所不同，但通常需要几个月的时间。

---

编辑

Amazon 刚刚宣布了 Target Tracking Policies，这就是在 CloudFormation 中使用单独的资源类型 AWS::ApplicationAutoScaling::ScalingPolicy 来实现的。

您仍需要为 DynamoDB 表配置特定的读写吞吐量，但需要单独配置读取扩展策略和写入另一个策略。

亚马逊在其文档中提供了以下示例。

{
  "Resources": {
    "DDBTable": {
      "Type": "AWS::DynamoDB::Table",
      "Properties": {
        "AttributeDefinitions": [
          {
            "AttributeName": "ArtistId",
            "AttributeType": "S"
          },
          {
            "AttributeName": "Concert",
            "AttributeType": "S"
          },
          {
            "AttributeName": "TicketSales",
            "AttributeType": "S"
          }
        ],
        "KeySchema": [
          {
            "AttributeName": "ArtistId",
            "KeyType": "HASH"
          },
          {
            "AttributeName": "Concert",
            "KeyType": "RANGE"
          }
        ],
        "GlobalSecondaryIndexes": [
          {
            "IndexName": "GSI",
            "KeySchema": [
              {
                "AttributeName": "TicketSales",
                "KeyType": "HASH"
              }
            ],
            "Projection": {
              "ProjectionType": "KEYS_ONLY"
            },
            "ProvisionedThroughput": {
              "ReadCapacityUnits": 5,
              "WriteCapacityUnits": 5
            }
          }
        ],
        "ProvisionedThroughput": {
          "ReadCapacityUnits": 5,
          "WriteCapacityUnits": 5
        }
      }
    },
    "WriteCapacityScalableTarget": {
      "Type": "AWS::ApplicationAutoScaling::ScalableTarget",
      "Properties": {
        "MaxCapacity": 15,
        "MinCapacity": 5,
        "ResourceId": { "Fn::Join": [
          "/",
          [
            "table",
            { "Ref": "DDBTable" }
          ]
        ] },
        "RoleARN": {
          "Fn::GetAtt": ["ScalingRole", "Arn"]
        },
        "ScalableDimension": "dynamodb:table:WriteCapacityUnits",
        "ServiceNamespace": "dynamodb"
      }
    },
    "ScalingRole": {
      "Type": "AWS::IAM::Role",
      "Properties": {
        "AssumeRolePolicyDocument": {
          "Version": "2012-10-17",
          "Statement": [
            {
              "Effect": "Allow",
              "Principal": {
                "Service": [
                  "application-autoscaling.amazonaws.com"
                ]
              },
              "Action": [
                "sts:AssumeRole"
              ]
            }
          ]
        },
        "Path": "/",
        "Policies": [
          {
            "PolicyName": "root",
            "PolicyDocument": {
              "Version": "2012-10-17",
              "Statement": [
                {
                  "Effect": "Allow",
                  "Action": [
                    "dynamodb:DescribeTable",
                    "dynamodb:UpdateTable",
                    "cloudwatch:PutMetricAlarm",
                    "cloudwatch:DescribeAlarms",
                    "cloudwatch:GetMetricStatistics",
                    "cloudwatch:SetAlarmState",
                    "cloudwatch:DeleteAlarms"
                  ],
                  "Resource": "*"
                }
              ]
            }
          }
        ]
      }
    },
    "WriteScalingPolicy": {
      "Type": "AWS::ApplicationAutoScaling::ScalingPolicy",
      "Properties": {
        "PolicyName": "WriteAutoScalingPolicy",
        "PolicyType": "TargetTrackingScaling",
        "ScalingTargetId": {
          "Ref": "WriteCapacityScalableTarget"
        },
        "TargetTrackingScalingPolicyConfiguration": {
          "TargetValue": 50.0,
          "ScaleInCooldown": 60,
          "ScaleOutCooldown": 60,
          "PredefinedMetricSpecification": {
            "PredefinedMetricType": "DynamoDBWriteCapacityUtilization"
          }
        }
      }
    }
  }
}

Answer 2

可以使用 CloudFormation 完成自动缩放。

请参阅此answer。

Answer 3

这似乎有效：

"ReadScaling" : {
  "Type" : "AWS::ApplicationAutoScaling::ScalableTarget",
  "Properties" : {
    "MaxCapacity" : "<MAX CAPACITY>,
    "MinCapacity" : "<MIN CAPACITY>,
    "ResourceId" : "table/<TABLE NAME>",
    "RoleARN" : "<IAM ROLE ARN>",
    "ScalableDimension" : "dynamodb:table:ReadCapacityUnits",
    "ServiceNamespace" : "dynamodb"
  }
},

"ReadScalingPolicy" : {
  "Type" : "AWS::ApplicationAutoScaling::ScalingPolicy",
  "Properties" : {
    "PolicyName" : "ReadScalingPolicy",
    "PolicyType" : "TargetTrackingScaling",
    "ResourceId" : "table/<TABLE NAME>",
    "ScalableDimension" : "dynamodb:table:ReadCapacityUnits",
    "ServiceNamespace" : "dynamodb",
    "TargetTrackingScalingPolicyConfiguration" : {
      "PredefinedMetricSpecification": {
        "PredefinedMetricType": "DynamoDBReadCapacityUtilization"
      },
      "ScaleInCooldown" : "60",
      "ScaleOutCooldown" : "60",
      "TargetValue" : "70"
    }
  },
  "DependsOn" : "ReadScaling"
},

有关 IAM 角色的规范，请参阅 http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/AutoScaling.CLI.html