Incremental updates of data in an S3 data lake - amazon-web-services

I'm new to AWS and coming from a Data Warehousing ETL background. We are currently moving to cloud using AWS services Data Lake and trying to load data into Amazon s3 landing layer (Bucket) from our external source RDBMS system using sqoop jobs and then to different layers (Buckets) in Amazon S3 using Informatica BDM.
The frequency of getting data from external source system is daily. I'm not sure how do we have to implement Delta load/SCD Types in S3. Is there any possibility to change an object after creating it in Amazon S3 bucket or do we have to keep creating copy of everyday load as an object in s3 bucket?
I understand Amazon gives us database options but we are directed to load data into Amazon S3.

Amazon S3 is simply a storage system. It will store whatever data is provided.
It is not possible to 'update' an object in Amazon S3. An object can be overwritten (replaced), but it cannot be appended.
Traditionally, information in data lakes are appended by adding additional files, such as a daily dump of information. Systems that process data out of the data lake normally process multiple files. In fact, this is a more efficient process since data can be processed in parallel rather than attempting to read a single, large file.
So, your system can either do a new, complete dump that replaces data or it can store additional files with the incremental data.
Another common practice is to partition data, which puts files into different directories such as a different directory per month or day or hour. This way, when a system processes data in the data lake, it only needs to read files in the directories that are known to contain data for a given time period. For example, if a query wishes to processes data for a given month, it only needs to read the directory with data for that month, thereby speeding the process. (Partitions can also be hierarchical, such as having directories for hour inside day inside month.)
To answer your question of "how do we have to implement Delta load/SCD Types in S3", it really depends on how you will use the data once it is in the data lake. It would be good to store the data in a manner that helps the system that will eventually consume it.

Related

How to automatically transfer newly added avro data from GCS to BigQuery

I want to schedule the data transfer job between Cloud Storage to BigQuery.
I have one application that dumps data continuously to the GCS bucket path (let's say gs://test-bucket/data1/*.avro) that I want to move to BigQuery as soon as the object is created in GCS.
I don't want to migrate all the files available within the folder again and again. I just want to move only the newly added object after the last run in the folder.
BigQuery data transfer service is available that takes Avro files as input but not a folder and it does not provide only newly added objects instead all.
I am new to it so might be missing some functionality, How can I achieve it?
Please note- I want to schedule a job to load data at a certain
frequency (every 10 or 15 min), I don't want any solution from a
trigger perspective since the number of objects that will be generated
will be huge.
You can use Cloud Function and Storage event trigger. Just launch Cloud Function that loads data into BigQuery when new file arrives.
https://cloud.google.com/functions/docs/calling/storage
EDIT: If you have more than 1500 loads per day you can workaround with loading using BQ Storage API.
If you do not need superb performance then you can just create an external table on that folder and query it instead loading every file.

Architecture to process AWS S3 files

I am working on a POC where we have millions of existing S3 compressed json files (uncompressed 3+ MB, with nested objects and arrays) and more being added every few minutes. We need to perform computations on top of the uncompressed data (per file basis) and store it to a DB table where we can then perform some column operations. The most common solution I found online is
S3 (Add/update event notification) => SQS (main queue => dlq queue) <=> AWS lambda
We have a DB table for all S3 bucket key names that are being successfully loaded, so I can query this table and use the AWS SDK Node.js package to send messages to the SQS main queue. For newly added/updated files, S3 event notification will take care of it.
I think the above architecture will work in my case, but are there any other AWS services I should look at?
I looked at AWS Athena which can read my compressed files and can give me the raw output but since I have big nested objects and arrays on top of which I need to perform computation, I am not sure if it's ideal to write such complex logic in SQL.
I would really appreciate some guidance here.
If you plan to query the data in the future in ways you can't anticipate, I would strongly suggest you explore the Athena solution, since you would be plugging a very powerful SQL engine on top of your data. Athena can query directly compressed json and export to other data formats that are a lot more efficient to query (like parquet or orc) and support complex data structures.
The flow would be:
S3 (new file) => Athena ETL (json to, say, parquet)
see e.g. here.
For already existing data you can do a one-off query to convert it to the appropriate format (partitioning would be useful if your data volume is big as it seems it is). Having good partitioning is key to obtain good performance on Athena and you will need to think carefully about it on your ETL. More on partitioning, e.g., there.

Database suggestion for large unstructured datasets to integrate with elasticsearch

A scenario where we have millions of records saved in database, currently I was using dynamodb for saving metadata(and also do write, update and delete operations on objects), S3 for storing files(eg: files can be images, where its associated metadata is stored in dynamoDb) and elasticsearch for indexing and searching. But due to dynamodb limit of 400kb for a row(a single object), it was not sufficient for data to be saved. I thought about saving for an object in different versions in dynamodb itself, but it would be too complicated.
So I was thinking for replacement of dynamodb with some better storage:
AWS DocumentDb
S3 for saving metadata also, along with object files
So which one is better option among both in your opinion and why, which is also cost effective. (Also easy to sync with elasticsearch, but this ES syncing is not much issue as somehow it is possible for both)
If you have any other better suggestions than these two you can also tell me those.
I would suggest looking at DocumentDB over Amazon S3 based on your use case for the following reasons:
Pricing of storing the data would be $0.023 for standard and $0.0125 for infrequent access per GB per month (whereas Document DB is $0.10per GB-month), depending on your size this could add up greatly. If you use IA be aware that your costs for retrieval could add up greatly.
Whilst you would not directly get the data down you would use either Athena or S3 Select to filter. Depending on the data size being queried it would take from a few seconds to possibly minutes (not the milliseconds you requested).
For unstructured data storage in S3 and the querying technologies around it are more targeted at a data lake used for analysis. Whereas DocumentDB is more driven for performance within live applications (it is a MongoDB compatible data store after all).

How to split data when archiving from AWS database to S3

For a project we've inherited we have a large-ish set of legacy data, 600GB, that we would like to archive, but still have available if need be.
We're looking at using the AWS data pipeline to move the data from the database to be in S3, according to this tutorial.
https://docs.aws.amazon.com/datapipeline/latest/DeveloperGuide/dp-object-copyactivity.html
However, we would also like to be able to retrieve a 'row' of that data if we find the application is actually using a particular row.
Apparently that tutorial puts all of the data from a table into a single massive CSV file.
Is it possible to split the data up into separate files, with 100 rows of data in each file, and giving each file a predictable file name, such as:
foo_data_10200_to_10299.csv
So that if we realise we need to retrieve row 10239, we can know which file to retrieve, and download just that, rather than all 600GB of the data.
If your data is stored in CSV format in Amazon S3, there are a couple of ways to easily retrieve selected data:
Amazon Athena is an interactive query service that makes it easy to analyze data in Amazon S3 using standard SQL.
S3 Select (currently in preview) enables applications to retrieve only a subset of data from an object by using simple SQL expressions.
These work on compressed (gzip) files too, to save storage space.
See:
Welcome - Amazon Athena
S3 Select and Glacier Select – Retrieving Subsets of Objects

Loading data (incrementally) into Amazon Redshift, S3 vs DynamoDB vs Insert

I have a web app that needs to send reports on its usage, I want to use Amazon RedShift as a data warehouse for that purpose,
How should i collect the data ?
Every time, the user interact with my app, i want to report that.. so when should i write the files to S3 ? and how many ?
What i mean is:
- If do not send the info immediately, then I might lose it as a result of a connection lost, or from some bug in my system while its been collected and get ready to be sent to S3...
- If i do write files to S3 on each user interaction, i will end up with hundreds of files (on each file has minimal data), that need to be managed, sorted, deleted after been copied to RedShift.. that dose not seems like a good solution .
What am i missing? Should i use DynamoDB instead, Should i use simple insert into Redshift instead !?
If i do need to write the data to DynamoDB, should i delete the hold table after been copied .. what are the best practices ?
On any case what are the best practices to avoid data duplication in RedShift ?
Appreciate the help!
It is preferred to aggregate event logs before ingesting them into Amazon Redshift.
The benefits are:
You will use the parallel nature of Redshift better; COPY on a set of larger files in S3 (or from a large DynamoDB table) will be much faster than individual INSERT or COPY of a small file.
You can pre-sort your data (especially if the sorting is based on event time) before loading it into Redshift. This is also improve your load performance and reduce the need for VACUUM of your tables.
You can accumulate your events in several places before aggregating and loading them into Redshift:
Local file to S3 - the most common way is to aggregate your logs on the client/server and every x MB or y minutes upload them to S3. There are many log appenders that are supporting this functionality, and you don't need to make any modifications in the code (for example, FluentD or Log4J). This can be done with container configuration only. The down side is that you risk losing some logs and these local log files can be deleted before the upload.
DynamoDB - as #Swami described, DynamoDB is a very good way to accumulate the events.
Amazon Kinesis - the recently released service is also a good way to stream your events from the various clients and servers to a central location in a fast and reliable way. The events are in order of insertion, which makes it easy to load it later pre-sorted to Redshift. The events are stored in Kinesis for 24 hours, and you can schedule the reading from kinesis and loading to Redshift every hour, for example, for better performance.
Please note that all these services (S3, SQS, DynamoDB and Kinesis) allow you to push the events directly from the end users/devices, without the need to go through a middle web server. This can significantly improve the high availability of your service (how to handle increased load or server failure) and the cost of the system (you only pay for what you use and you don't need to have underutilized servers just for logs).
See for example how you can get temporary security tokens for mobile devices here: http://aws.amazon.com/articles/4611615499399490
Another important set of tools to allow direct interaction with these services are the various SDKs. For example for Java, .NET, JavaScript, iOS and Android.
Regarding the de-duplication requirement; in most of the options above you can do that in the aggregation phase, for example, when you are reading from a Kinesis stream, you can check that you don't have duplications in your events, but analysing a large buffer of events before putting into the data store.
However, you can do this check in Redshift as well. A good practice is to COPY the data into a staging tables and then SELECT INTO a well organized and sorted table.
Another best practice you can implement is to have a daily (or weekly) table partition. Even if you would like to have one big long events table, but the majority of your queries are running on a single day (the last day, for example), you can create a set of tables with similar structure (events_01012014, events_01022014, events_01032014...). Then you can SELECT INTO ... WHERE date = ... to each of this tables. When you want to query the data from multiple days, you can use UNION_ALL.
One option to consider is to create time series tables in DynamoDB where you create a table every day or week in DynamoDB to write every user interaction. At the end of the time period (day, hour or week), you can copy the logs on to Redshift.
For more details, on DynamoDB time series table see this pattern: http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/GuidelinesForTables.html#GuidelinesForTables.TimeSeriesDataAccessPatterns
and this blog:
http://aws.typepad.com/aws/2012/09/optimizing-provisioned-throughput-in-amazon-dynamodb.html
For Redshift DynamoDB copy: http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/RedshiftforDynamoDB.html
Hope this helps.
Though there is already an accepted answer here, AWS launched a new service called Kinesis Firehose which handles the aggregation according to user defined intervals, a temporary upload to s3 and the upload (SAVE) to redshift, retries and error handling, throughput management,etc...
This is probably the easiest and most reliable way to do so.
You can write data to CSV file on local disk and then run Python/boto/psycopg2 script to load data to Amazon Redshift.
In my CSV_Loader_For_Redshift I do just that:
Compress and load data to S3 using boto Python module and multipart upload.
conn = boto.connect_s3(AWS_ACCESS_KEY_ID,AWS_SECRET_ACCESS_KEY)
bucket = conn.get_bucket(bucket_name)
k = Key(bucket)
k.key = s3_key_name
k.set_contents_from_file(file_handle, cb=progress, num_cb=20,
reduced_redundancy=use_rr )
Use psycopg2 COPY command to append data to Redshift table.
sql="""
copy %s from '%s'
CREDENTIALS 'aws_access_key_id=%s;aws_secret_access_key=%s'
DELIMITER '%s'
FORMAT CSV %s
%s
%s
%s;""" % (opt.to_table, fn, AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY,opt.delim,quote,gzip, timeformat, ignoreheader)
Just being a little selfish here and describing exactly what Snowplow ,an event analytics platform does. They use this awesome unique way of collecting event logs from the client and aggregating it on S3.
They use Cloudfront for this. What you can do is, host a pixel in one of the S3 buckets and put that bucket behind a CloudFront distribution as an origin. Enable logs to an S3 bucket for the same CloudFront.
You can send logs as url parameters whenever you call that pixel on your client (similar to google analytics). These logs can then be enriched and added to Redshift database using Copy.
This solves the purpose of aggregation of logs. This setup will handle all of that for you.
You can also look into Piwik which is an open source analytics service and see if you can modify it specific to your needs.