使用Serverless框架部署AWS Lambda时遭遇S3事件规则重叠错误的排查求助

问题描述 #

我正在尝试使用Serverless框架部署AWS Lambda，我的serverless.yaml配置如下：

provider:
  name: aws
  runtime: python3.8
  region: us-west-2
  stackName: ${self:service}-${self:custom.name}-${opt:stage, 'dev'}
  stackTags:
    Service: "it"
  lambdaHashingVersion: 20201221
  memorySize: 128
  timeout: 900
  logRetentionInDays: 14
  disableDefaultOutputExportNames: true
  deploymentBucket: ${self:custom.deployment-s3-bucket}
  environment:
    S3_BUCKET: ${self:custom.bucket}
    S3_BUCKET_PATH_PREFIX: ${self:custom.path_prefix}
    REDSHIFT_DATABASE: ${self:custom.database}
    REDSHIFT_SCHEMA: ${self:custom.schema}
    REDSHIFT_TABEL_PREFIX: ${self:custom.table_prefix}
    REDSHIFT_USER: ${self:custom.user}
    REDSHIFT_PASSWORD: ${self:custom.password}
    REDSHIFT_PORT: ${self:custom.port}
    REDSHIFT_ENDPOINT: ${self:custom.endpoint}
    REDSHIFT_ROLE: ${self:custom.role}
  iam:
    role:
      name: s3-to-redshift-load
      statements:
        - Effect: Allow
          Action:
            - s3:GetObject
          Resource: "arn:aws:s3:::${self:custom.bucket}/*"
functions:
  load:
    handler: handler.run
    events:
      - s3: #https://www.serverless.com/framework/docs/providers/aws/events/s3#using-existing-buckets
          bucket: ${self:custom.bucket}
          event: s3:ObjectCreated:*
          rules:
            - prefix: ${self:custom.path_prefix}/
            - suffix: .json
          existing: true

但在部署时出现以下错误：

Serverless Error
----------------------------------------
An error occurred: LoadCustomS31 - Received response status [FAILED] from custom resource. Message returned: Configuration is ambiguously defined. Cannot have overlapping suffixes in two rules if the prefixes are overlapping for the same event type. See details in CloudWatch Log: 2021/08/30/[$LATEST]4f4f9ec564544ebb979576ed1b6b2879 (RequestId: 317ecd1c-b699-4799-8060-5168e1947e3c).

请问我哪里配置出错了？

问题分析与解决方案 #

这个错误的核心原因是你对S3事件规则的配置方式不符合AWS的要求：你把prefix和suffix拆成了两个独立的rules数组元素，AWS会将它们识别为两条并行的触发规则。

这两条规则针对同一个事件类型（s3:ObjectCreated:*），且规则的匹配范围存在重叠——比如一个路径为${self:custom.path_prefix}/test.json的文件会同时满足两条规则的条件，AWS无法明确该用哪条规则触发Lambda，因此判定配置模糊并报错。

修复方法 #

你需要把prefix和suffix合并到同一个规则对象中，这样它们就会形成一条“与”规则：只有当S3对象同时满足前缀和后缀条件时，才会触发Lambda函数。

修改后的functions部分配置如下：

functions:
  load:
    handler: handler.run
    events:
      - s3:
          bucket: ${self:custom.bucket}
          event: s3:ObjectCreated:*
          rules:
            - prefix: ${self:custom.path_prefix}/
              suffix: .json
          existing: true

配置说明 #

修改后的规则逻辑非常明确：仅当S3桶中创建的对象路径以${self:custom.path_prefix}/开头，并且以.json结尾时，才会触发你的load Lambda函数。这种组合规则不存在范围重叠，AWS可以清晰识别触发条件，也就不会再抛出模糊配置的错误了。

内容的提问来源于stack exchange，提问作者rp346