我正在定义一个与DynamoDB表相关的API/服务。我有一些索引（被定义为全局二级索引），以支持一些查询。我已经设计好了表格，包括GSI定义和看起来正确的查询。然而，在进行查询时，我收到了此异常：
{ AccessDeniedException: User: arn:aws:sts::OBSCURED:assumed-role/chatroom-application-dev-us-east-1-lambdaRole/chatroom-application-dev-getRoomMessages is not authorized to perform: dynamodb:Query on resource: arn:aws:dynamodb:us-east-1:OBSCURED:table/messages-table-dev/index/roomIndex
at Request.extractError (/var/task/node_modules/aws-sdk/lib/protocol/json.js:48:27)
at Request.callListeners (/var/task/node_modules/aws-sdk/lib/sequential_executor.js:105:20)
at Request.emit (/var/task/node_modules/aws-sdk/lib/sequential_executor.js:77:10)
at Request.emit (/var/task/node_modules/aws-sdk/lib/request.js:683:14)
at Request.transition (/var/task/node_modules/aws-sdk/lib/request.js:22:10)
at AcceptorStateMachine.runTo (/var/task/node_modules/aws-sdk/lib/state_machine.js:14:12)
at /var/task/node_modules/aws-sdk/lib/state_machine.js:26:10
at Request.<anonymous> (/var/task/node_modules/aws-sdk/lib/request.js:38:9)
at Request.<anonymous> (/var/task/node_modules/aws-sdk/lib/request.js:685:12)
at Request.callListeners (/var/task/node_modules/aws-sdk/lib/sequential_executor.js:115:18)
message: 'User: arn:aws:sts::OBSCURED:assumed-role/chatroom-application-dev-us-east-1-lambdaRole/chatroom-application-dev-getRoomMessages is not authorized to perform: dynamodb:Query on resource: arn:aws:dynamodb:us-east-1:OBSCURED:table/messages-table-dev/index/roomIndex',
code: 'AccessDeniedException',
time: 2018-06-02T22:05:46.110Z,
requestId: 'OBSCURED',
statusCode: 400,
retryable: false,
retryDelay: 30.704899664776054 }
在异常的顶部，显示了我的 getRoomMessages 方法的 ARN 未被授权执行 dynamodb:Query 操作的信息，并显示了全局二级索引的 ARN。
显然，需要定义策略以授予访问全局二级索引的权限。但是如何操作并不明显。我看到其他关于 DynamoDB 的 StackOverflow 问题抱怨文档过于零散，很难找到任何信息。我不得不同意。 "零散" 这个词用得太含蓄了。
我正在使用 Serverless Framework。下面是 provider 部分显示的策略/角色定义：
provider:
name: aws
runtime: nodejs8.10
stage: dev
region: us-east-1
iamRoleStatements:
- Effect: Allow
Action:
- dynamodb:Query
- dynamodb:Scan
- dynamodb:GetItem
- dynamodb:PutItem
- dynamodb:UpdateItem
- dynamodb:DeleteItem
Resource:
- { "Fn::GetAtt": ["MessagesDynamoDBTable", "Arn" ] }
- { "Fn::GetAtt": ["#roomIndex", "Arn" ] }
- { "Fn::GetAtt": ["#userIndex", "Arn" ] }
environment:
MESSAGES_TABLE: ${self:custom.tableName}
在“资源”部分，我认为我应该列出声明权限的资源。第一个引用整个表格。我刚添加了最后两个，并引用索引。
编辑：当我运行“serverless deploy”时，会打印以下消息：
The CloudFormation template is invalid: Template error: instance of Fn::GetAtt references undefined resource #roomIndex
我尝试了几种不同的方式，但结果都是相同的错误。问题实质上是 - 在
serverless.yml 中，如何使用 Cloudfront 语法获取索引的 ARN。由于 ARN 在异常中显示，所以 ARN 是存在的。DynamoDB 表定义：
resources:
Resources:
MessagesDynamoDBTable:
Type: AWS::DynamoDB::Table
Properties:
AttributeDefinitions:
- AttributeName: messageId
AttributeType: S
- AttributeName: room
AttributeType: S
- AttributeName: userId
AttributeType: S
KeySchema:
- AttributeName: messageId
KeyType: HASH
GlobalSecondaryIndexes:
- IndexName: roomIndex
KeySchema:
- AttributeName: room
KeyType: HASH
Projection:
ProjectionType: ALL
ProvisionedThroughput:
ReadCapacityUnits: 1
WriteCapacityUnits: 1
- IndexName: userIndex
KeySchema:
- AttributeName: userId
KeyType: HASH
Projection:
ProjectionType: ALL
ProvisionedThroughput:
ReadCapacityUnits: 1
WriteCapacityUnits: 1
ProvisionedThroughput:
ReadCapacityUnits: 1
WriteCapacityUnits: 1
TableName: ${self:custom.tableName}
以上异常对应的查询:
{
"TableName": "messages-table-dev",
"IndexName": "roomIndex",
"KeyConditionExpression": "#roomIndex = :room",
"ExpressionAttributeNames": {
"#roomIndex": "room"
},
"ExpressionAttributeValues": {
":room": {
"S": "everyone"
}
}
}
以下是生成查询的Lambda函数代码片段：
app.get('/messages/room/:room', (req, res) => {
const params = {
TableName: MESSAGES_TABLE,
IndexName: "roomIndex",
KeyConditionExpression: '#roomIndex = :room',
ExpressionAttributeNames: { '#roomIndex': 'room' },
ExpressionAttributeValues: {
":room": { S: `${req.params.room}` }
},
};
console.log(`QUERY ROOM ${JSON.stringify(params)}`);
dynamoDb.query(params, (error, result) => {
if (error) {
console.log(error);
res.status(400).json({ error: 'Could not get messages' });
} else {
res.json(result.Items);
}
});
});