Update readme. Includes Java 21 patch

Signed-off-by: Prabhu Subramanian <prabhu@appthreat.com>

README.md

@@ -15,7 +15,7 @@ chen container image has everything needed to get started.
 
 ### Jupyter notebook with docker compose
 
-Use the docker compose from this repo to try chennai with Jupyter notebook.
+Use the docker compose from this repo to try chennai with Jupyter Notebook.
 
 ```shell
 git clone https://github.com/AppThreat/chen
@@ -69,7 +69,7 @@ To download the chen distribution.
 chen --download
 ```
 
-To generate custom graphs and models with atom for data science, download the scientific pack which installs support for PyTorch ecosystem. [conda](https://docs.conda.io/projects/conda/en/stable/user-guide/install/index.html) is recommended for best experience.
+To generate custom graphs and models with atom for data science, download the scientific pack which installs support for the PyTorch ecosystem. [conda](https://docs.conda.io/projects/conda/en/stable/user-guide/install/index.html) is recommended for the best experience.
 
 ```shell
 chen --download --with-science
@@ -176,7 +176,7 @@ chennai> help
 1 error found
 ```
 
-This error is mostly due to missing python .so (linux), .dll (windows) or .dylib (mac) file. Ensure the below environment variables below are set correctly.
+This error is mostly due to missing python .so (linux), .dll (windows) or .dylib (mac) file. Ensure the environment variables below are set correctly.
 
 - SCALAPY_PYTHON_LIBRARY - Use values such as python3.10, python3.11 based on the version installed. On Windows, there are no dots. python311
 - JAVA_TOOL_OPTIONS - jna.library.path must be set to the python lib directory

contrib/README.md

@@ -0,0 +1,8 @@
+# Introduction
+
+chen works better under Java 21 with virtual threads. Use the provided patch for Java 21.
+
+```shell
+git apply --ignore-space-change --ignore-whitespace contrib/java21.patch
+sbt clean stage createDistribution
+```

contrib/java21.patch

@@ -0,0 +1,39 @@
+diff --git a/build.sbt b/build.sbt
+index 30f005d..16e9759 100644
+--- a/build.sbt
++++ b/build.sbt
+@@ -41,18 +41,18 @@ ThisBuild / libraryDependencies ++= Seq(
+ ThisBuild / compile / javacOptions ++= Seq(
+   "-g", // debug symbols
+   "-Xlint",
+-  "--release=17"
++  "--release=21"
+ ) ++ {
+   // fail early if users with JDK8 try to run this
+   val javaVersion = sys.props("java.specification.version").toFloat
+-  assert(javaVersion.toInt >= 17, s"this build requires JDK17+ - you're using $javaVersion")
++  assert(javaVersion.toInt >= 21, s"this build requires JDK21+ - you're using $javaVersion")
+   Nil
+ }
+
+ ThisBuild / scalacOptions ++= Seq(
+   "-deprecation", // Emit warning and location for usages of deprecated APIs.
+   "--release",
+-  "17",
++  "21",
+ )
+
+
+diff --git a/dataflowengineoss/src/main/scala/io/appthreat/dataflowengineoss/queryengine/Engine.scala b/dataflowengineoss/src/main/scala/io/appthreat/dataflowengineoss/queryengine/Engine.scala
+index 00c4297..97822ab 100644
+--- a/dataflowengineoss/src/main/scala/io/appthreat/dataflowengineoss/queryengine/Engine.scala
++++ b/dataflowengineoss/src/main/scala/io/appthreat/dataflowengineoss/queryengine/Engine.scala
+@@ -28,7 +28,7 @@ class Engine(context: EngineContext):
+
+     private val logger: Logger = LoggerFactory.getLogger(this.getClass)
+     private val executorService: ExecutorService =
+-        Executors.newWorkStealingPool(2)
++        Executors.newVirtualThreadPerTaskExecutor()
+     private val completionService =
+         new ExecutorCompletionService[TaskSummary](executorService)
+