I've seen plenty of examples of how to read JSON and parquet files using structured streaming, but I have some transactions that gets input into a database. How do I read that data that coming into that table?
I know it's a vague question but I couldn't find any examples online for this so I wasn't sure how to ask the question. I need to get that data and perform some aggregation on it in real time.
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I just started using scala-spark. I want to read the data from MongoDB as well as the streaming data which will be sent to MongoDB. I know there are different functions to read data from MongoDB like "spark.read.mongo" and a separate function to stream data using "spark.readStream". But I want to know is there a way in which I do both of them simultaneously.
PS: I tried searching for the same in stack overflow but couldn't find any. If there is already a similar question please direct me to the same.
I have a use-case where i want to capture the data changes (Insert/Update) in Hbase tables which is getting populated via Kafka.
I have tried the following approach but it doesn't seem to work. Hbase change data capture
Is there any other way i can achieve the task.
In regards to: https://cloud.google.com/bigquery/streaming-data-into-bigquery#dataavailability
What's the best way to programatically determine if a table's data is available after streaming?
I am getting unexpected results trying to fetch Rows and TotalRows with the following apis: Jobs.Query, Jobs.GetQueryResults, Tables.Get, Tabledata.List
Thanks.
You can tell whether data is flushed on the table by executing the Tables.Get() API and looking at the streamingBuffer.oldestEntryTime value. This can be considered a high-water mark of data that has been flushed out of the buffer.
Any data before this timestamp should be available for copy, export, and list operations.
Also, I should clarify that data in the table is available for query immediately after streaming. It only is unavailable to table copy, export, and tabledata.list() operations. Yes, this is confusing, but yes, we're also working on addressing the problem.
For tables that haven't been streamed to before or recently, there is a warmup period where new streaming data won't show up.
See https://cloud.google.com/bigquery/streaming-data-into-bigquery#dataavailability for more information.
I have a database currently in Mongo running on an EC2 instance and would like to migrate the data to DynamoDB. Is this possible and what is the most cost effective way to achieve this?
When you ask for a "cost effective way" to migrate data, I assume you are looking for existing technologies that can ease your life. If so, you could do the following:
Export your MongoDB data to a text file, say in tsv format, using mongoexport.
Upload that file somewhere in S3.
Import this data, in S3, to DynamoDB using AWS Data Pipeline.
Of course, you should design & finalize your DynamoDB table schema before doing all this.
Whenever you are changing databases, you have to be very careful about the way you migrate data. Certain data formats maintain type consistency, while others do not.
Then there are just data formats that cannot handle your schema. For example, CSV is great at handling data when it is one row per entry, but how do you render an embedded array in CSV? It really isn't possible, JSON is good at this, but JSON has its own problems.
The easiest example of this is JSON and DateTime. JSON does not have a specification for storing DateTime values, they can end up as ISO8601 dates, or perhaps UNIX Epoch Timestamps, or really anything a developer can dream up. What about Longs, Doubles, Ints? JSON doesn't discriminate, it makes them all strings, which can cause loss of precision if not deserialized correctly.
This makes it very important that you choose the appropriate translation medium. The generally means you have to roll your own solution. This means loading up the drivers for both databases, reading an entry from one, translating, and writing to this other. This is the best way to be absolutely sure errors are handled properly for your environment, that types are kept consistently, and that the code properly translates schema from source to destination (if necessary).
What does this all mean for you? It means a lot of leg work for you. It is possible somebody has already rolled something that is broad enough for your case, but I have found in the past that it is best for you to do it yourself.
I know this post is old, Amazon made it possible with AWS DMS, check this document :
https://docs.aws.amazon.com/dms/latest/userguide/CHAP_Source.MongoDB.html
Some relevant parts:
Using an Amazon DynamoDB Database as a Target for AWS Database
Migration Service
You can use AWS DMS to migrate data to an Amazon DynamoDB table.
Amazon DynamoDB is a fully managed NoSQL database service that
provides fast and predictable performance with seamless scalability.
AWS DMS supports using a relational database or MongoDB as a source.
We have a few collections in mongodb that we wish to transfer to redshift (on an automatic incremental daily basis).
How can we do it? Should we export the mongo to csv?
I wrote some code to export data from Mixpanel into Redshift for a client. Initially the client was exporting to Mongo but we found Redshift offered very large performance improvements for query. So first of all we transferred the data out of Mongo into Redshift, and then we came up with a direct solution that transfers the data from Mixpanel to Redshift.
To store JSON data in Redshift first you need to create a SQL DDL to store the schema in Redshift i.e. a CREATE TABLE script.
You can use a tool like Variety to help as it can give you some insight into your Mongo schema. However it does struggle with big datasets - you might need to subsample your dataset.
Alternatively DDLgenerator can generate DDL from various sources including CSV or JSON. This also struggles with large datasets (well the dataset I was dealing with was 120GB).
So in theory you could use MongoExport to generate CSV or JSON from Mongo and then run it through DDL generator to get a DDL.
In practice I found using JSON export a little easier because you don't need to specify the fields you want to extract. You need to select the JSON array format. Specifically:
mongoexport --db <your db> --collection <your_collection> --jsonArray > data.json
head data.json > sample.json
ddlgenerator postgresql sample.json
Here - because I am using head - I use a sample of the data to show the process works. However, if your database has schema variation, you want to compute the schema based on the whole database which could take several hours.
Next you upload the data into Redshift.
If you have exported JSON, you need to use Redshift's Copy from JSON feature. You need to define a JSONpath to do this.
For more information check out the Snowplow blog - they use JSONpaths to map the JSON on to a relational schema. See their blog post about why people might want to read JSON to Redshift.
Turning the JSON into columns allows much faster query than the other approaches such as using JSON EXTRACT PATH TEXT.
For incremental backups, it depends if data is being added or data is changing. For analytics, it's normally the former. The approach I used is to export the analytic data once a day, then copy it into Redshift in an incremental fashion.
Here are some related resources although in the end I did not use them:
Spotify has a open-source project called Luigi - this code claims to upload JSON to Redshift but I haven't used it so I don't know if it works.
Amiato have a web page that says they offer a commercial solution for loading JSON data into Redshift - but there is not much information beyond that.
This blog post discusses performing ETL on JSON datasources such as Mixpanel into Redshift.
Related Redit question
Blog post about dealing with JSON arrays in Redshift
Honestly, I'd recommend using a third party here. I've used Panoply (panoply.io) and would recommend it. It'll take your mongo collections and flatten them into their own tables in redshift.
AWS Database Migration Service(DMS) Adds Support for MongoDB and Amazon DynamoDB.So I think now onward best option to migrate from MongoDB to Redshift is DMS.
MongoDB versions 2.6.x and 3.x as a database source
Document Mode and Table Mode supported
Supports change data capture(CDC)
Details - http://docs.aws.amazon.com/dms/latest/userguide/CHAP_Source.MongoDB.html
A few questions that would be helpful to know would be:
Is this an add-only always increasing incremental sync i.e. data is only being added and not being updated / removed or rather your redshift instance is interested only in additions?
Is the data inconsistency due to delete / updates happening at source and not being fed to redshift instance ok?
Does it need to be daily-incremental batch or can it be realtime as it is happening as well?
Depending on your situation may be mongoexport works for you, but you have to understand the shortcoming of it, which can be found at http://docs.mongodb.org/manual/reference/program/mongoexport/ .
I had to tackle the same issue (not on a daily basis though).
as ask mentioned, You can use mongoexport in order to export the data, but keep in mind that redshift doesn't support arrays, so in case your collections data contains arrays you'll find it a bit problematic.
My solution to this was to pipe the mongoexport into a small utility program I wrote that transforms the mongoexport json rows into my desired csv output.
piping the output also allows you to make the process parallel.
Mongoexport allows you to add a mongodb query to the command, so if your collection data supports it you can spawn N different mongoexport processes, pipe it's results into the other program and decrease the total runtime of the migration process.
Later on, I uploaded the files to S3, and performed a COPY into the relevant table.
This should be a pretty easy solution.
Stitch Data is the best tool ever I've ever seen to replicate incrementally from MongoDB to Redshift within a few clicks and minutes.
Automatically and dynamically Detect DML, DDL for tables for replication.