The asynchronous progress tracking and correctness issue fixes presented in the previous blog posts are not the single new feature in Apache Spark Structured Streaming 3.4.0. There are many others but to keep the blog post readable, I'll focus here only on 3 of them.
Apache Spark is infamous for its correctness issue for chained stateful operations. Fortunately things get improved in each release. The most recent one, the 3.4.0, also got some important changes on that field!
Finally, the time has come to start the analysis of the new features in Apache Spark. The first of them that grabbed my attention was the Async progress tracking from Structured Streaming.
Even though the Project Lightspeed is not there yet, Apache Spark Structured Streaming 3.3.0 has several interesting features that should make your daily life easier.
Unit tests are the backbone of modern software but they only verify a particular unit of the application. What to do if we wanted to check the interaction between all these units? One of the solutions are automated integration tests. While they are relatively easy to implement against data in-rest, they are more challenging for streaming scenarios.
Structured Streaming micro-batch mode inherits a lot of features from the batch part. Apart from the retry mechanism presented previously, it also has the same auto-scaling logic relying on the Dynamic Resource Allocation.
Last year I wrote a blog post about broadcasting in Structured Streaming and I got an interesting question under one of the demo videos. What happens if the joined static dataset in a broadcast mode gets new data? Let's check this out!
Unexpected things happen and sooner or later, any pipeline can fail. Hopefully, sometimes the errors may be temporary and automatically recovered after some retries. What if the job is a streaming one? Let's see here how Apache Spark Structured Streaming handles task retries in micro-batch and continuous modes!
After previous blog posts focusing on 2 specific Structured Streaming features, it's time to complete them with a list of other changes made in the 3.2.0 version!
Initially I wanted to include the session windows in the blog post about Structured Streaming changes. But I changed my mind when I saw how many things it involves!
It's big news for Apache Spark Structured Streaming users. RocksDB is now available as a Vanilla Spark-backed state store backend!
The topic of this post brought Luan Carvalho who shared with me an Open Source project connecting Apache Spark to Apache Kafka Schema Registry. Initially, I wanted to exclusively focus on the project but on my way I discovered some other interesting points.
At first glance, the update operation in an arbitrary stateful application looks just like another map's put function. However, it has an impact on what happens later with the state store. In this blog post, you will see an example that can eventually help you to reduce an I/O pressure of the updates.
If you've used Apache Kafka source in Structured Streaming, you undoubtedly noticed a property called maxOffsetsPerTrigger. According to the documentation, it helps to "limit on maximum number of offsets processed per trigger interval". My initial reaction to this property was, "Cool! We can enforce idempotent processing". I was not wrong, but the blog post will show you that I wasn't entirely right either!
Even though Apache Kafka supports transactional producers, they're not present in Apache Spark Kafka sink. But despite that, is it possible to implement a transactional producer in Apache Spark Structured Streaming? You should see that at the end of this article.
State store is a critical part of any stateful Structured Streaming application. It's important to know what happens when your business logic and input data interact with it. State store metrics will provide you some key insight into this interaction. If you don't know them now, no worries, it's the topic of this blog post!
If you read my blog post, you certainly noticed that very often I get lost on the internet. Fortunately, very often it helps me write blog posts. But the internet is not the only place where I can get lost. It also happens to me to do that with Apache Spark code and one of my most recent confusions was about FileSystem and FileContext classes.
Aside from the joins presented in the previous blog post, Structured Streaming also got a few other interesting new features that I will present here.
In the previous blog post, you discovered what changed for joins in Apache Spark 3.1. If you remember the summary sentence, it was not the single join changes in this new release. Apart from them, you can also do a bit more with Structured Streaming joins!
After the introductory part, it's time to share what I learned from the custom state store implementation.