AWS Appsync Multi-table BatchPutItem Returns 空

Question

我一直在按照教程进行批量操作： https://docs.aws.amazon.com/appsync/latest/devguide/tutorial-dynamodb-batch.html#multi-table-batch

当我尝试进行多 table 批处理时，即使对象已成功提交到 dynamodb，我也得到了空响应。

这是我的突变：

mutation sendReadings {
  recordReadings(
    tempReadings: [
      {sensorId: 1, value: 85.5, timestamp: "2018-02-01T17:21:05.000+08:00"},
      {sensorId: 2, value: 85.7, timestamp: "2018-02-01T17:21:06.000+08:00"},
      {sensorId: 3, value: 85.8, timestamp: "2018-02-01T17:21:07.000+08:00"},
      {sensorId: 4, value: 84.2, timestamp: "2018-02-01T17:21:08.000+08:00"},
      {sensorId: 5, value: 81.5, timestamp: "2018-02-01T17:21:09.000+08:00"}
    ]
    locReadings: [
      {sensorId: 1, lat: 47.615063, long: -122.333551, timestamp: "2018-02-01T17:21:05.000+08:00"},
      {sensorId: 2, lat: 47.615163, long: -122.333552, timestamp: "2018-02-01T17:21:06.000+08:00"}
      {sensorId: 3, lat: 47.615263, long: -122.333553, timestamp: "2018-02-01T17:21:07.000+08:00"}
      {sensorId: 4, lat: 47.615363, long: -122.333554, timestamp: "2018-02-01T17:21:08.000+08:00"}
      {sensorId: 5, lat: 47.615463, long: -122.333555, timestamp: "2018-02-01T17:21:09.000+08:00"}
    ]) {
    locationReadings {
      sensorId
      timestamp
      lat
      long
    }
    temperatureReadings {
      sensorId
      timestamp
      value
    }
  }
}

问题是响应returns null:

{
  "data": {
    "recordReadings": {
      "locationReadings": null,
      "temperatureReadings": null
    }
  }
}

请求映射模板：

## Convert tempReadings arguments to DynamoDB objects
#set($tempReadings = [])
#foreach($reading in ${ctx.args.tempReadings})
    $util.qr($tempReadings.add($util.dynamodb.toMapValues($reading)))
#end

## Convert locReadings arguments to DynamoDB objects
#set($locReadings = [])
#foreach($reading in ${ctx.args.locReadings})
    $util.qr($locReadings.add($util.dynamodb.toMapValues($reading)))
#end

{
    "version" : "2018-05-29",
    "operation" : "BatchPutItem",
    "tables" : {
        "LocationReadingTable": $utils.toJson($locReadings),
        "TemperatureReadingTable": $utils.toJson($tempReadings)
    }
}

响应映射模板：

## If there was an error with the invocation
## there might have been partial results
#if($ctx.error)
    ## Append a GraphQL error for that field in the GraphQL response
    $utils.appendError($ctx.error.message, $ctx.error.message)
#end
## Also returns data for the field in the GraphQL response
$utils.toJson($context.result.data)

代码与教程几乎相同。我检查了日志，正在发送响应，但没有被捕获，所以要么我的代码已关闭，要么 AWS 方面存在错误。任何人都可以重现这个或在执行 multi-table BatchPutItem 时能够得到响应吗？

Answer 1

感谢您提出非常详细的问题，它确实帮助我调试了您的问题。因此，为了解决您的问题，您需要调整您的响应映射模板。最后，我能够用空响应重现该问题。原因是 multi-table 批量放置响应的形状是这种格式：

"result": {
    "data": {
        "TemperatureReadingTable": [
            {
                "value": 85.5,
                "sensorId": "1",
                "timestamp": "2018-02-01T17:21:05.000+08:00"
            },
            {
                "value": 85.7,
                "sensorId": "2",
                "timestamp": "2018-02-01T17:21:06.000+08:00"
            },
            {
                "value": 85.8,
                "sensorId": "3",
                "timestamp": "2018-02-01T17:21:07.000+08:00"
            },
            {
                "value": 84.2,
                "sensorId": "4",
                "timestamp": "2018-02-01T17:21:08.000+08:00"
            },
            {
                "value": 81.5,
                "sensorId": "5",
                "timestamp": "2018-02-01T17:21:09.000+08:00"
            }
        ],
        "LocationReadingTable": [
            {
                "lat": 47.615063,
                "long": -122.333551,
                "sensorId": "1",
                "timestamp": "2018-02-01T17:21:05.000+08:00"
            },
            {
                "lat": 47.615163,
                "long": -122.333552,
                "sensorId": "2",
                "timestamp": "2018-02-01T17:21:06.000+08:00"
            },
            {
                "lat": 47.615263,
                "long": -122.333553,
                "sensorId": "3",
                "timestamp": "2018-02-01T17:21:07.000+08:00"
            },
            {
                "lat": 47.615363,
                "long": -122.333554,
                "sensorId": "4",
                "timestamp": "2018-02-01T17:21:08.000+08:00"
            },
            {
                "lat": 47.615463,
                "long": -122.333555,
                "sensorId": "5",
                "timestamp": "2018-02-01T17:21:09.000+08:00"
            }
        ]
    },

因此，$context.result.data 将为您 return 一个 object，其字段为 TemperatureReadingTable 和 LocationReadingTable。但是，您正在应用 $util.toJson 来解析类型 RecordResult，其中 temperatureReadings 和 locationReadings 作为 child 字段。

请使用以下定义更新您的响应映射模板，它将适用于您：

  #if($ctx.error)
      ## Append a GraphQL error for that field in the GraphQL response
      $utils.appendError($ctx.error.message, $ctx.error.message)
  #end

  {
      "temperatureReadings": $util.toJson(${ctx.result.data.TemperatureReadingTable}),
      "locationReadings": $util.toJson(${ctx.result.data.LocationReadingTable})
  }

此外，我鼓励您从控制台的“设置”页面启用 CloudWatch 日志，并选择 ALL。这将记录 Request/Response headers、已解决的 Request/Response 模板、跟踪信息等。因此它将帮助您通过查看 [=32= 的内容来快速识别此类问题] 模板。

感谢您提出这个问题，如果没有提到这个，我们会更新文档。

AWS Appsync Multi-table BatchPutItem Returns 空

AWS Appsync Multi-table BatchPutItem Returns Null

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