只有在s3中上传了多个文件之后，才可以触发lambda的方法吗 [英] Is there a way to trigger lambda only after multiple files have uploaded in s3
问题描述
一个用户将多个文件上传到我的S3存储桶中，并以当天作为所有文件的前缀.仅在收到前缀下的所有文件后，才需要触发lambda函数.我该怎么办?.
A user uploads multiple files into my S3 bucket with the current day as prefix for all the files. I need to trigger a lambda function only after I have received all the files under the prefix. How can I do that?.
推荐答案
创建DynamoDb表以跟踪上载的部分.您应该使用HASH键存储文件的前缀或类似的东西.另一个属性可能是零件数.
Create a DynamoDb table to keep track of the uploaded parts. You should use a HASH key to store the prefix of the files, or something like that. Another attribute could be a count of parts.
在上载的每个部分上，将调用一个lambda并将以这种方式更新表上的记录:
On each part uploaded, a lambda will be called and it will update the record at the table in this way:
-
读取记录.
Read the record.
如果该记录不存在，则使用条件表达式仅在该记录仍然不存在时使用count = 1创建它.这是为了避免一个lambda覆盖另一个lambda.
If the record does not exist, create it, with count = 1, using a conditional expression to create only if the record still not exists. This is to avoid one lambda overriding another.
- 如果出现错误，请返回1.
如果记录存在，请使用条件表达式对它进行递增计数以仅在计数等于从1读取的计数时进行更新.
If the record exists, update it incrementing the count with the conditional expression to update only if the count is equal the count read on 1.
- 如果出现错误，请返回1.
达到预期计数时，请调用lambda对其进行处理.
When you reach the expected count, invoke the lambda to process it.
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