I am new to Spark but I am reading up as much as I can. I have a small project where multiple data files (in gzip) are going to continuously land in an S3 bucket every hour. I need to be able to open/read these gzip files and consolidate/aggregate data across them. So, I need to look at them in a holistic fashion. How, what techniques and tools from Amazon AWS can be used? Do I create interim files in a S3 folder or hold Dataframes in memory or use some database and blow away the data after each hour? So, I am looking for ideas more than a piece of code.
So far, in AWS, I have written a pyspark script that reads 1 file at a time and create an output file back in output S3 folder. But that leaves me with multiple output files for each hour. Would be nice if there was 1 file for a given hour.
From technology perspective, I am using an EMR cluster with just 1 master and 1 core node, Pyspark and S3.
Thanks
You could use an AWS Glue ETL job written in PySpark. Glue jobs can be scheduled to run every hour.
I suggest reading the entire dataset, performing your operations, and then moving the data to another long-term storage location.
If you are working on a few GB of data, a PySpark job should complete within minutes. There's no need to keep an EMR cluster running for an hour if you'll only need it for 10 minutes. Consider using short-lived EMR clusters or a Glue ETL job.
Athena supports querying GZipped data. If you're performing some sort of analysis, maybe executing an Athena query with a time range will work?
You could also use a CTAS (Create Table As Select) statement in Athena to copy data to a new location, and performing basic ETL on it at the same time.
What exactly does your PySpark code do?
Related
I am looking for advice which service should I use. I am new to big data and confused with differences between them on AWS.
Use case:
I receive 60-100 csv files daily (each one can be from few MB to few GB). There are six corresponding schemas, and each file can be treated as part of only one table.
I need to load those files to the six database tables and execute joins between them and generate daily output. After generation of the output, the data present in database is no longer need, so we can truncate that tables and await on the next day.
Files have predictable naming patterns:
A_<timestamp1>.csv goes to A table
A_<timestamp2>.csv goes to A table
B_<timestamp1>.csv goes to B table
etc ...
Which service could be used for that purpose?
AWS Redshift (execute here joins)
AWS Glue (load to redshift)
AWS EMR (spark)
or maybe something else? I heard that spark could be used to do the joins, but what is the proper, optimal and performant way of doing that?
Edit:
Thanks for the responses. I see two options for now:
Use AWS Glue, setup 6 crawlers which will load on trigger files to specific AWS Glue Data Catalogs, execute SQL joins with Athena
Use AWS Glue, setup 6 crawlers which will load on trigger files to specific AWS Glue Data Catalogs, trigger spark job (AWS Glue in serverless form) to do the SQL joins and setup output to the S3.
Edit 2:
But according to the: https://carbonrmp.com/knowledge-hub/tech-engineering/athena-vs-spark-lessons-from-implementing-a-fully-managed-query-system/
Presto is designed for low latency and uses a massively parallel processing (MPP) approach which is fast but requires everything to happen at once and in memory. It’s all or nothing, if you run out of memory, then “Query exhausted resources at this scale factor”. Spark is designed for scalability and follows a map-reduce design [1]. The job is split and processed in chunks, which are generally processed in batches. If you double the workload without changing the resource, it should take twice as long instead of failing [2]
So Athena (aka Presto) is not scalable as much as I want. I've seen "Query exhausted resources at this scale factor" for my case.
Any possibility of changing the file type to a columnar format like parquet? Then you can use AWS EMR and spark should be able to handle the joins easily. Obviously, you need to optimize the query depending on the data/cluster size etc.
I am trying to automate an ETL pipeline that outputs data from AWS RDS MYSQL to AWS S3. I am currently using AWS Glue to do the job. When I do an initial load from RDS to S3. It captures all the data in the file which is exactly what I want. However, when I add new data to the MYSQL database and run the Glue job again. I get an empty file instead of the added rows. Any help would be MUCH appreciated.
Bookmarking rules for JDBC Sources are here. Important point to remember for JDBC sources is that values have to be increasing or decreasing order and Glue only processes new data from last checkpoint.
Typically, either an autogenerated sequence number or a datatime used as key for bookmarking
For anybody who is still struggling with this (it drove me mad, because i thought my spark code was wrong), disable bookmarking in job details.
I'm working on a task of copying csv files from s3 bucket to redshift. I've found multiple ways to do so but I'm not sure which one will be the best possible way to do it. Here's the scenario:
On regular intervals, multiple CSV files of size around 500 MB - 1 GB, will be added to my s3 bucket. The data can contain duplicates. The task is to copy the data to redshift table while ensuring that the duplicate data is not present in redshift.
Here are the ways I found which can be used:
Create a AWS Lambda function which will be triggered whenever a file is added to s3 bucket.
Use AWS Kinesis
Use AWS Glue
I understand Lambda should not be used for jobs that takes more than 5 minutes. So should I use it or just eliminate this option?
Kinesis can handle large amount of data but is it the best way to do it?
I'm not familiar with Glue and Kinesis. But I read that Glue can be slow.
If anyone can point me to the right direction, it will be really helpful.
You can definitely make it work with Lambda, if you leverage StepFunctions and the S3 Select option to filter subsets of data into smaller chunks. You'd have your Step Functions manage your ETL orchestration wherein you execute your lambdas that selectively pull from the large data file via the S3 select option. Your pre-process state--see links below--could be used to determine execution requirements, then execute multiple Lambdas, even in parallel, if you wish. Those lambdas would process the subsets of data to remove dups and perform any other ETL operations you might require. Then, you'd take the processed data and write to Redshift. Here are links that will help you put that architecture together:
Trigger State Machine Execution from S3 Event
Manage Lambda Processing Executions and workflow state
Use S3 Select to pull subsets from large data objects
Also, here's a link to a Python ETL pipeline example for the CDK that I built. You'll see an example of an S3 event-driven lambda along with data processing and DDB or MySQL writes. Will give you an idea as to how you can build out comprehensive Lambdas for ETL operations. You would just need to add a psycopg2 layer to your deployment for Redshift. Hope this helps.
I'm doing designing some ETL data pipelines with Airflow. Data transformations is done by provisioning an AWS EMR Spark cluster and sending its some jobs. The jobs read data from S3, process them and write them back to S3 using date as a partition.
For my last step, I need to load the S3 data to a datawarehouse using SQL scripts that are submitted to Redshift using Python script, however I cannot find a clean way to get retrieve which data need to be loaded, ie. which date partitions have been generated during Spark transformations (can only be known during the execution of the job and not beforehand).
Note that everything is orchestrated through a Python script using boto3 library that is run from a corporate VM that cannot be accessed from outside.
What would be the best way to fetch this information from EMR?
For now I'm thinking about different solutions:
- Write the information into a log file. Get the data from Spark master node using SSH through Python script
- Write the information to an S3 file
- Write the information to a database (RDS?)
I'm struggling to determine what are the pros and the cons of these solutions. I'm also wondering what would be the best way to inform that data transformations is over and that metadata can be fetched.
Thanks in advance
The most straightforward is to use S3 as your temporary storage. After finishing your Spark execution (Writing result to S3), you can add one more step writing data to S3 bucket which you want to get in next step.
The approach with RDS should be the similar to S3, but it requires more implementations than S3. You need to setup RDS, maintain Schema, implementation to work with RDS...
With S3 tmp file, after EMR terminated and AF running next step, using Boto to fetch that tmp file (S3 Path depends on your requirement) and that is it.
I have a use case wherein I want to take a data from DynamoDB and do some transformation on the data. After this I want to create 3 csv files (there will be 3 transformations on the same data) and dump them to 3 different s3 locations.
My architecture would be sort of following:
Is it possible to do so? I can't seem to find any documentation regarding it. If it's not possible using pipeline, are there any other services which could help me with my use case?
These dumps will be scheduled daily. My other consideration was using aws lamda. But according to my understanding, it's event based triggered rather time based scheduling, is that correct?
Yes it is possible but not using HiveActivity instead EMRActivity. If you look into Data pipeline documentation for HiveActivity, it clearly states its purpose and not suits your use case:
Runs a Hive query on an EMR cluster. HiveActivity makes it easier to set up an Amazon EMR activity and automatically creates Hive tables based on input data coming in from either Amazon S3 or Amazon RDS. All you need to specify is the HiveQL to run on the source data. AWS Data Pipeline automatically creates Hive tables with ${input1}, ${input2}, and so on, based on the input fields in the HiveActivity object.
Below is how your data pipeline should look like. There is also a inbuilt template Export DynamoDB table to S3 in UI for AWS Data Pipeline which creates the basic structure for you, and then you can extend/customize to suit your requirements.
To your next question using Lambda, Of course lambda can be configured to have event based triggering or schedule based triggering, but I wouldn't recommend using AWS Lambda for any ETL operations as they are time bound & usual ETLs are longer than lambda time limits.
AWS has specific optimized feature offerings for ETLs, AWS Data Pipeline & AWS Glue, I would always recommend to choose between one of two. In case your ETL involves data sources not managed within AWS compute and storage services OR any speciality use case which can't be sufficed by above two options, then AWS Batch will be my next consideration.
Thanks amith for your answer. I have been busy for quite some time now. I did some digging after you posted your answer. Turns out we can dump the data to different s3 locations using Hive activity as well.
This is how the data pipeline would like in that case.
But I believe writing multiple hive activities, when your input source is DynamoDB table, is not a good idea since hive doesn't load any data in memory. It does all the computations on the actual table which could deteriorate the performance of the table. Even documentation suggests to export the data incase you need to make multiple queries to same data. Reference
Enter a Hive command that maps a table in the Hive application to the data in DynamoDB. This table acts as a reference to the data stored in Amazon DynamoDB; the data is not stored locally in Hive and any queries using this table run against the live data in DynamoDB, consuming the table’s read or write capacity every time a command is run. If you expect to run multiple Hive commands against the same dataset, consider exporting it first.
In my case I needed to perform different type of aggregations on the same data once a day. Since dynamoDB doesn't support aggregations, I turned to Data pipeline using Hive. In the end we ended up using AWS Aurora which is My-SQL based.