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gianm merged 1 commit into from
Aug 30, 2022
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Add Java 17 information to documentation. #12990

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29 changes: 24 additions & 5 deletions docs/operations/java.md
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Expand Up @@ -27,8 +27,8 @@ a Java runtime for Druid.

## Selecting a Java runtime

Druid fully supports Java 8 and 11. The project team recommends Java 11. The project team does not recommend running
with Java 17, because certain Druid functionality is not currently compatible with Java 17.
Druid fully supports Java 8 and 11, and has experimental support for [Java 17](#java-17).
The project team recommends Java 11.

The project team recommends using an OpenJDK-based Java distribution. There are many free and actively-supported
distributions available, including
Expand Down Expand Up @@ -70,15 +70,13 @@ Druid, because Java 8 does not recognize these parameters and fails to start up
To do this, add the following lines to your `jvm.config` files:

```
--add-exports=java.base/jdk.internal.perf=ALL-UNNAMED
--add-exports=java.base/jdk.internal.ref=ALL-UNNAMED
--add-exports=java.base/jdk.internal.misc=ALL-UNNAMED
--add-opens=java.base/java.lang=ALL-UNNAMED
--add-opens=java.base/java.io=ALL-UNNAMED
--add-opens=java.base/java.nio=ALL-UNNAMED
--add-opens=java.base/jdk.internal.ref=ALL-UNNAMED
--add-opens=java.base/sun.nio.ch=ALL-UNNAMED
--add-opens=jdk.management/com.sun.management.internal=ALL-UNNAMED
```

Additionally, tasks run by [MiddleManagers](../design/architecture.md) execute in separate JVMs. The command line for
Expand All @@ -87,8 +85,29 @@ these JVMs is given by `druid.indexer.runner.javaOptsArray` or `druid.indexer.ru
a line like the following:

```
druid.indexer.runner.javaOptsArray=["-server","-Xms1g","-Xmx1g","-XX:MaxDirectMemorySize=1g","-Duser.timezone=UTC","-Dfile.encoding=UTF-8","-XX:+ExitOnOutOfMemoryError","-Djava.util.logging.manager=org.apache.logging.log4j.jul.LogManager","--add-exports=java.base/jdk.internal.perf=ALL-UNNAMED","--add-exports=java.base/jdk.internal.ref=ALL-UNNAMED","--add-exports=java.base/jdk.internal.misc=ALL-UNNAMED","--add-opens=java.base/java.lang=ALL-UNNAMED","--add-opens=java.base/java.io=ALL-UNNAMED","--add-opens=java.base/java.nio=ALL-UNNAMED","--add-opens=java.base/jdk.internal.ref=ALL-UNNAMED","--add-opens=java.base/sun.nio.ch=ALL-UNNAMED","--add-opens=jdk.management/com.sun.management.internal=ALL-UNNAMED"]
druid.indexer.runner.javaOptsArray=["-server","-Xms1g","-Xmx1g","-XX:MaxDirectMemorySize=1g","-Duser.timezone=UTC","-Dfile.encoding=UTF-8","-XX:+ExitOnOutOfMemoryError","-Djava.util.logging.manager=org.apache.logging.log4j.jul.LogManager","--add-exports=java.base/jdk.internal.ref=ALL-UNNAMED","--add-exports=java.base/jdk.internal.misc=ALL-UNNAMED","--add-opens=java.base/java.lang=ALL-UNNAMED","--add-opens=java.base/java.io=ALL-UNNAMED","--add-opens=java.base/java.nio=ALL-UNNAMED","--add-opens=java.base/jdk.internal.ref=ALL-UNNAMED","--add-opens=java.base/sun.nio.ch=ALL-UNNAMED"]
```

The `Xms`, `Xmx`, and `MaxDirectMemorySize` parameters in the line above are merely an example. You may use different
values in your specific environment.

## Java 17

Druid has experimental support for Java 17.

An important change in Java 17 is that [strong encapsulation](#strong-encapsulation) is enabled by default. The various
`--add-opens` and `--add-exports` parameters listed in the [strong encapsulation](#strong-encapsulation) section are
required in all `jvm.config` files and in `druid.indexer.runner.javaOpts` or `druid.indexer.runner.javaOptsArray` on
MiddleManagers. Failure to include these parameters leads to failure of various operations.

In addition, Druid's launch scripts detect Java 17 and log the following message rather than starting up:

```
Druid requires Java 8 or 11. Your current version is: 17.X.Y.
```

You can skip this check with an environment variable:

```
export DRUID_SKIP_JAVA_CHECK=1
```
2 changes: 0 additions & 2 deletions examples/bin/run-java
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Expand Up @@ -31,14 +31,12 @@ then
# Must disable strong encapsulation for certain packages on Java 17.
exec "$JAVA_BIN" \
--add-exports=java.base/jdk.internal.misc=ALL-UNNAMED \
--add-exports=java.base/jdk.internal.perf=ALL-UNNAMED \
--add-exports=java.base/jdk.internal.ref=ALL-UNNAMED \
--add-opens=java.base/jdk.internal.ref=ALL-UNNAMED \
--add-opens=java.base/java.nio=ALL-UNNAMED \
--add-opens=java.base/sun.nio.ch=ALL-UNNAMED \
--add-opens=java.base/java.io=ALL-UNNAMED \
--add-opens=java.base/java.lang=ALL-UNNAMED \
--add-opens=jdk.management/com.sun.management.internal=ALL-UNNAMED \
"$@"
elif [ "$JAVA_MAJOR" != "" ] && [ "$JAVA_MAJOR" -ge "11" ]
then
Expand Down
4 changes: 0 additions & 4 deletions pom.xml
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Expand Up @@ -1690,10 +1690,6 @@
</activation>
<properties>
<jdk.surefire.argLine>
<!-- required for JvmMonitor on Java 11+ -->
--add-exports=java.base/jdk.internal.perf=ALL-UNNAMED
--add-opens=jdk.management/com.sun.management.internal=ALL-UNNAMED

<!-- required for DataSketches Memory on Java 11+ -->
--add-exports=java.base/jdk.internal.ref=ALL-UNNAMED
--add-exports=java.base/jdk.internal.misc=ALL-UNNAMED
Expand Down