go - 并行执行 DynamoDB 查询(全局二级索引的 BatchGetItems)

Question

这里的想法是在查询通过 GSI 运行时并行运行多个 DynamoDB 查询。截至目前 BatchGetItems doesn't support querying over Indexes推荐的方法是并行查询数据。我正在使用带有 wg 的 go routines 来并行处理例程的执行。

函数的输入是一个带有 ID 的字符串数组，输出是 ID 的属性。

当函数在本地运行时，没有问题，但是当函数在AWS-Lambda上运行时，返回的数据不断增长；

即；输入 2 项应输出 2 项。如果函数在 AWS-Lambda 上测试，

• 函数第一次返回 2 项
• 第二次返回 4 个项目(相同的项目重复 2 次)
• 第三次返回 6 个项目(相同的项目重复 4 次)

等等。这是代码片段。每次运行 lambda 时，是否有什么没有正确处理让 lambda 输出额外的数据集？

package main

import (
    "context"
    "fmt"
    "os"
    "sync"
    "github.com/aws/aws-lambda-go/lambda"
    "github.com/aws/aws-sdk-go/aws"
    "github.com/aws/aws-sdk-go/aws/session"
    "github.com/aws/aws-sdk-go/service/dynamodb"
    "github.com/aws/aws-sdk-go/service/dynamodb/dynamodbattribute"
)

//Final Output Interface
var bulkOutput []interface{}

func exitWithError(err error) {
    fmt.Fprintln(os.Stderr, err)
    os.Exit(1)
}

//LambdaInputJSON input for the lambda handler
type LambdaInputJSON struct {
    Ids      []string `json:"ids,omitempty"`
}

//HandleRequest : Lambda entry point
func HandleRequest(ctx context.Context, data LambdaInputJSON) ([]interface{}, error) {
    return DynamoDBBatchGetRecords(data), nil
}

func main() {
    lambda.Start(HandleRequest)
}

func DynamoDBBatchGetRecords(a LambdaInputJSON) []interface{} {

    var wg sync.WaitGroup
    var mutex = &sync.Mutex{}

    iterations := len(a.Ids)
    wg.Add(iterations)
    for i := 0; i < iterations; i++ {
        go QueryOutput(a.Ids[i], &wg, mutex)
    }

    wg.Wait()
    return bulkOutput

}

//QueryOutput GoRoutine
func QueryOutput(data string, wg *sync.WaitGroup, mtx *sync.Mutex) {
    var outputData []interface{}
    defer wg.Done()
    sess, err := session.NewSession(&aws.Config{
        Region: aws.String("aws-region"),
    })
    if err != nil {
        exitWithError(fmt.Errorf("failed to make Query API call, %v", err))
    }
    ddb := dynamodb.New(sess)
    queryInput := &dynamodb.QueryInput{
        Limit:                aws.Int64(1),
        TableName:            aws.String("table-name"),
        IndexName:            aws.String("gsi-index"),
        ScanIndexForward:     aws.Bool(false),
        ConsistentRead:       aws.Bool(false),
        KeyConditions: map[string]*dynamodb.Condition{
            "column_name": {
                ComparisonOperator: aws.String("EQ"),
                AttributeValueList: []*dynamodb.AttributeValue{
                    {
                        S: aws.String(data),
                    },
                },
            },
        },
    }
    output, err := ddb.Query(queryInput)
    if err != nil {
        exitWithError(fmt.Errorf("Failed to make Query API call, %v", err))
    }
    err = dynamodbattribute.UnmarshalListOfMaps(output.Items, &outputData)
    if err != nil {
        exitWithError(fmt.Errorf("Failed to unmarshal Query result items, %v", err))
    }
    mtx.Lock()
    bulkOutput = append(bulkOutput, outputData)
    mtx.Unlock()
}

Answer 1

根据 documentation ，全局变量独立于您的 Lambda 函数的处理程序代码。这导致缓冲区随着时间的推移而增加。

修正后的引用粘贴在下方。

package main

import (
    "context"
    "fmt"
    "os"
    "sync"

    "github.com/aws/aws-lambda-go/lambda"
    "github.com/aws/aws-sdk-go/aws"
    "github.com/aws/aws-sdk-go/aws/session"
    "github.com/aws/aws-sdk-go/service/dynamodb"
    "github.com/aws/aws-sdk-go/service/dynamodb/dynamodbattribute"
)

func exitWithError(err error) {
    fmt.Fprintln(os.Stderr, err)
    os.Exit(1)
}

//HandleRequest : Lambda entry point
func HandleRequest(ctx context.Context, data LambdaInputJSON) ([]interface{}, error) {
    output := DynamoDBBatchGetRecords(data)
    return output, nil
}

func main() {
    lambda.Start(HandleRequest)
}

func DynamoDBBatchGetRecords(a LambdaInputJSON) []interface{} {
    var dataOut []interface{}
    var wg = &sync.WaitGroup{}
    var mtx = &sync.Mutex{}

    iterations := len(a.Ids)
    wg.Add(iterations)
    for i := 0; i < i; i++ {
        go func(i int) {
            defer wg.Done()
            var outputData []interface{}
            sess, err := session.NewSession(&aws.Config{
                Region: aws.String("aws-region"),
            })
            if err != nil {
                exitWithError(fmt.Errorf("failed to make Query API call, %v", err))
            }
            ddb := dynamodb.New(sess)
            queryInput := &dynamodb.QueryInput{
                Limit:            aws.Int64(1),
                TableName:        aws.String("table"),
                IndexName:        aws.String("index"),
                ScanIndexForward: aws.Bool(false),
                ConsistentRead: aws.Bool(false),
                KeyConditions: map[string]*dynamodb.Condition{
                    "index-column": {
                        ComparisonOperator: aws.String("EQ"),
                        AttributeValueList: []*dynamodb.AttributeValue{
                            {
                                S: aws.String(a.Ids[i]),
                            },
                        },
                    },
                },
            }
            output, err := ddb.Query(queryInput)

            if err != nil {
                exitWithError(fmt.Errorf("E1 failed to make Query API call, %v", err))
            }
            err = dynamodbattribute.UnmarshalListOfMaps(output.Items, &outputData)
            if err != nil {
                exitWithError(fmt.Errorf("E2 failed to unmarshal Query result items, %v", err))
            }

            mtx.Lock()
            dataOut = append(dataOut, outputData[0])
            mtx.Unlock()

        }(i)
    }
    wg.Wait()
    return dataOut
}