aws Glue 作业：如何合并 s3 中的多个输出 .csv 文件

Question

我创建了 aws Glue Crawler 和作业。目的是将数据从 postgres RDS 数据库表传输到 S3 中的一个 .csv 文件。一切正常，但我在 S3 中总共收到 19 个文件。除了其中包含一行数据库表和标题的三个文件外，每个文件都是空的。因此数据库的每一行都会写入单独的 .csv 文件。我可以在这里做什么来指定我只需要一个文件，其中第一行是标题，然后是数据库的每一行？

import sys
from awsglue.transforms import *
from awsglue.utils import getResolvedOptions
from pyspark.context import SparkContext
from awsglue.context import GlueContext
from awsglue.job import Job

## @params: [JOB_NAME]
args = getResolvedOptions(sys.argv, ['JOB_NAME'])

sc = SparkContext()
glueContext = GlueContext(sc)
spark = glueContext.spark_session
job = Job(glueContext)
job.init(args['JOB_NAME'], args)
## @type: DataSource
## @args: [database = "gluedatabse", table_name = "postgresgluetest_public_account", transformation_ctx = "datasource0"]
## @return: datasource0
## @inputs: []
datasource0 = glueContext.create_dynamic_frame.from_catalog(database = "gluedatabse", table_name = "postgresgluetest_public_account", transformation_ctx = "datasource0")
## @type: ApplyMapping
## @args: [mapping = [("password", "string", "password", "string"), ("user_id", "string", "user_id", "string"), ("username", "string", "username", "string")], transformation_ctx = "applymapping1"]
## @return: applymapping1
## @inputs: [frame = datasource0]
applymapping1 = ApplyMapping.apply(frame = datasource0, mappings = [("user_id", "string", "user_id", "string"), ("username", "string", "username", "string"),("password", "string", "password", "string")], transformation_ctx = "applymapping1")
## @type: DataSink
## @args: [connection_type = "s3", connection_options = {"path": "s3://BUCKETNAMENOTSHOWN"}, format = "csv", transformation_ctx = "datasink2"]
## @return: datasink2
## @inputs: [frame = applymapping1]
datasink2 = glueContext.write_dynamic_frame.from_options(frame = applymapping1, connection_type = "s3", connection_options = {"path": "s3://BUCKETNAMENOTSHOWN"}, format = "csv", transformation_ctx = "datasink2")
job.commit()

数据库长这个样子： Databse图片

在 S3 中看起来像这样： S3 Bucket

S3 中的一个示例 .csv 如下所示：

password,user_id,username
346sdfghj45g,user3,dieter

正如我所说，每个表行都有一个文件。

编辑：到 s3 的分段上传似乎无法正常工作。它只是上传各个部分，但完成后不会将它们合并在一起。以下是作业日志的最后几行： 以下是日志的最后几行：

19/04/04 13:26:41 INFO ShuffleBlockFetcherIterator: Getting 0 non-empty blocks out of 1 blocks
19/04/04 13:26:41 INFO ShuffleBlockFetcherIterator: Started 0 remote fetches in 1 ms
19/04/04 13:26:41 INFO Executor: Finished task 16.0 in stage 2.0 (TID 18). 2346 bytes result sent to driver
19/04/04 13:26:41 INFO MultipartUploadOutputStream: close closed:false s3://bucketname/run-1554384396528-part-r-00018
19/04/04 13:26:41 INFO MultipartUploadOutputStream: close closed:true s3://bucketname/run-1554384396528-part-r-00017
19/04/04 13:26:41 INFO MultipartUploadOutputStream: close closed:false s3://bucketname/run-1554384396528-part-r-00019
19/04/04 13:26:41 INFO Executor: Finished task 17.0 in stage 2.0 (TID 19). 2346 bytes result sent to driver
19/04/04 13:26:41 INFO MultipartUploadOutputStream: close closed:true s3://bucketname/run-1554384396528-part-r-00018
19/04/04 13:26:41 INFO Executor: Finished task 18.0 in stage 2.0 (TID 20). 2346 bytes result sent to driver
19/04/04 13:26:41 INFO MultipartUploadOutputStream: close closed:true s3://bucketname/run-1554384396528-part-r-00019
19/04/04 13:26:41 INFO Executor: Finished task 19.0 in stage 2.0 (TID 21). 2346 bytes result sent to driver
19/04/04 13:26:41 INFO CoarseGrainedExecutorBackend: Driver commanded a shutdown
19/04/04 13:26:41 INFO CoarseGrainedExecutorBackend: Driver from 172.31.20.76:39779 disconnected during shutdown
19/04/04 13:26:41 INFO CoarseGrainedExecutorBackend: Driver from 172.31.20.76:39779 disconnected during shutdown
19/04/04 13:26:41 INFO MemoryStore: MemoryStore cleared
19/04/04 13:26:41 INFO BlockManager: BlockManager stopped
19/04/04 13:26:41 INFO ShutdownHookManager: Shutdown hook called
End of LogType:stderr

Answer 1

你可以尝试以下方法吗？

import sys
from awsglue.transforms import *
from awsglue.utils import getResolvedOptions
from pyspark.context import SparkContext
from awsglue.context import GlueContext
from awsglue.job import Job

## @params: [JOB_NAME]
args = getResolvedOptions(sys.argv, ['JOB_NAME'])

sc = SparkContext()
glueContext = GlueContext(sc)
spark = glueContext.spark_session
job = Job(glueContext)
job.init(args['JOB_NAME'], args)

datasource0 = glueContext.create_dynamic_frame.from_catalog(database = "gluedatabse", table_name = "postgresgluetest_public_account", transformation_ctx = "datasource0")

applymapping1 = ApplyMapping.apply(frame = datasource0, mappings = [("user_id", "string", "user_id", "string"), ("username", "string", "username", "string"),("password", "string", "password", "string")], transformation_ctx = "applymapping1")

## Force one partition, so it can save only 1 file instead of 19
repartition = applymapping1.repartition(1)

datasink2 = glueContext.write_dynamic_frame.from_options(frame = repartition, connection_type = "s3", connection_options = {"path": "s3://BUCKETNAMENOTSHOWN"}, format = "csv", transformation_ctx = "datasink2")
job.commit()

另外，如果您想检查当前有多少个分区，可以尝试以下代码。我猜有 19 个，这就是为什么将 19 个文件保存回 s3：

 ## Change to Pyspark Dataframe
 dataframe = DynamicFrame.toDF(applymapping1)
 ## Print number of partitions   
 print(dataframe.rdd.getNumPartitions())
 ## Change back to DynamicFrame
 datasink2 = DynamicFrame.fromDF(dataframe, glueContext, "datasink2")