sjwiesman commented on a change in pull request #508:
URL: https://github.com/apache/flink-web/pull/508#discussion_r810273744
##########
File path: _posts/2022-02-22-scala-free.md
##########
@@ -0,0 +1,77 @@
+---
+layout: post
+title: "Scala Free in One Fifteen"
+date: 2022-02-22 00:00:00
+authors:
+- sjwiesman:
+ name: "Seth Wiesman"
+ twitter: "sjwiesman"
+excerpt: Apache Flink's runtime is now Scala free, allowing users to leverage
any Scala version in their user code - including Scala 3!
+---
+
+Flink 1.15 is right around the corner, and among the many improvements is a
Scala free classpath.
+Users can now leverage the Java API from any Scala version, including Scala 3!
+
+<figure style="margin-left:auto;margin-right:auto;display:block;padding-top:
20px;padding-bottom:20px;width:75%;">
+ <img src="{{ site.baseurl
}}/img/blog/2022-02-22-scala-free/flink-scala-3.jpeg">
+ <figcaption style="padding-top: 10px;text-align:center"><b>Fig.1</b> Flink
1.15 Scala 3 Example</figcaption>
+</figure>
+
+This blog will discuss what has historically made supporting multiple Scala
versions so complex, how we achieved this milestone, and the future of Scala in
Apache Flink.
+
+{% toc %}
+
+## The Classpath and Scala
+
+If you have worked with a JVM-based application, you have probably heard the
term classpath.
+The classpath defines where the JVM will search for a given classfile when it
needs to be loaded.
+There may only be one instance of a classfile on each classpath, forcing any
dependency Flink exposes onto users.
+That is why the Flink community works hard to keep our classpath "clean" - or
free of unnecessary dependencies.
+We achieve this through a combination of [shaded
dependencies](https://github.com/apache/flink-shaded), [child first class
loading](https://nightlies.apache.org/flink/flink-docs-stable/docs/ops/debugging/debugging_classloading/#inverted-class-loading-and-classloader-resolution-order),
and a [plugins
abstraction](https://nightlies.apache.org/flink/flink-docs-stable/docs/deployment/filesystems/plugins/)
for optional components.
+
+The Apache Flink runtime is primarily written in Java but contains critical
components that forced Scala on the default classpath.
+And because Scala does not maintain binary compatibility across minor
releases, this historically required cross-building components for all versions
of Scala.
+But due to many reasons - [breaking changes in the
compiler](https://github.com/scala/scala/releases/tag/v2.12.8), [a new standard
library](https://www.scala-lang.org/news/2.13.0), and [a reworked macro
system](https://docs.scala-lang.org/scala3/guides/macros/macros.html) - this
was easier said than done.
+
+## Hiding Scala
+
+As mentioned above, Flink uses Scala in a few key components; Mesos
integration, the serialization stack, RPC, and the table planner.
+Instead of removing these dependencies or finding ways to cross-build them,
the community hid Scala.
+It still exists in the codebase but no longer leaks into the user code
classloader.
+
+In 1.14, we took our first steps in hiding Scala from our users.
+In 1.14, we took our first steps in hiding Scala from our users. We dropped
the support for Apache Mesos, partially implemented in Scala, which Kubernetes
very much eclipsed in terms of adoption.
Review comment:
```suggestion
We dropped the support for Apache Mesos, partially implemented in Scala,
which Kubernetes very much eclipsed in terms of adoption.
```
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: issues-unsubscr...@flink.apache.org
For queries about this service, please contact Infrastructure at:
us...@infra.apache.org
