question Re: Getting java warning after staring NiFi in Support Questions

Getting java warning after staring NiFi

tono425 — Fri, 13 Dec 2024 05:57:13 GMT

Hello,

Recently I setup NiFi 2.0.
Everytime I start NiFi, I get below warning messages in /var/log/messages.

Dec 13 12:07:58 myserver nifi.sh[208489]: WARNING: A restricted method in java.lang.foreign.Linker has been called Dec 13 12:07:58 myserver nifi.sh[208489]: WARNING: java.lang.foreign.Linker::downcallHandle has been called by org.apache.lucene.store.PosixNativeAccess in an unnamed module Dec 13 12:07:58 myserver nifi.sh[208489]: WARNING: Use --enable-native-access=ALL-UNNAMED to avoid a warning for callers in this module Dec 13 12:07:58 myserver nifi.sh[208489]: WARNING: Restricted methods will be blocked in a future release unless native access is enabled

Is there any way to supress these messages?

Here are product versions.

Red Hat Enterprise Linux 8.8
NiFi 2.0.0
Java OpenJDK 23.0.1.0.11

Regards,

Re: Getting java warning after staring NiFi

DianaTorres — Fri, 13 Dec 2024 15:56:33 GMT

@MattWho @steven-matison Hi! Do you have some insights here? Thanks!

Re: Getting java warning after staring NiFi

MattWho — Fri, 13 Dec 2024 16:48:24 GMT

@tono425

Apache NiFi 2.0.0 has only been tested and verified against Java 21. I suggest switching to latest Java 21 JDK update and seeing if same messages persist in your Linux /var/log/messages log.

NiFi 2.0.0 System requirements

Please help our community thrive. If you found any of the suggestions/solutions provided helped you with solving your issue or answering your question, please take a moment to login and click "Accept as Solution" on one or more of them that helped.

Thank you,
Matt

Re: Getting java warning after staring NiFi

tono425 — Mon, 16 Dec 2024 02:15:40 GMT

@MattWho
Thank you for your advice.
I installed Java 21 (21.0.5) but similar warnings still persist.

Dec 16 11:09:10 myserver nifi.sh[253936]: WARNING: A restricted method in java.lang.foreign.Linker has been called Dec 16 11:09:10 myserver nifi.sh[253936]: WARNING: java.lang.foreign.Linker::downcallHandle has been called by the unnamed module Dec 16 11:09:10 myserver nifi.sh[253936]: WARNING: Use --enable-native-access=ALL-UNNAMED to avoid a warning for this module

Thank you,

Re: Getting java warning after staring NiFi

MattWho — Mon, 16 Dec 2024 13:08:51 GMT

@tono425

It is just a WARNING that can safely be ignored.

I found some threads on this here:

https://bugs.openjdk.org/browse/JDK-8310626

https://apachenifi.slack.com/archives/C0L9VCD47/p1730736181056549?thread_ts=1730294478.475309&cid=C0L9VCD47

https://www.reddit.com/r/java/comments/17cjajl/why_introduce_a_mandatory_enablenativeaccess/

I suppose you could try adding a new java.arg.<some string/num> to the NiFi bootstrap.conf to "--enable-native-access=ALL-UNNAMED" to see if that stops these Warnings on NiFi startup.

Thank you,
Matt

Re: Getting java warning after staring NiFi

Shelton — Tue, 17 Dec 2024 15:48:15 GMT

@tono425
The error messages you are encountering in NiFi are related to Java's native method access restrictions introduced in newer Java versions (likely Java 17 or higher). These warnings indicate that NiFi (or a dependency like Apache Lucene) is calling restricted native methods that require explicit permission to access low-level operating system functions.
The warning mentions java.lang.foreign.Linker::downcallHandle, which is a native method used for low-level interactions with the operating system.
Here are the 3 options you should try to resolve the issue:

Option 1: Add the Java Option to Enable Native Access

Update the NiFi startup configuration to allow unrestricted native access for unnamed modules.

Edit the NiFi Java options in the bootstrap.conf file:

nano /opt/nifi/conf/bootstrap.conf 2. Add the following option to the java.arg properties:
java.arg.X=-enable-native-access=ALL-UNNAMED 3. Restart NiFi:

sudo systemctl restart nifi

Option 2: Use a Lower Java Version (if possible)

If NiFi was previously running fine with an earlier Java version (e.g., Java 8 or 11), you can revert to it until you're ready to address the native access changes:
Update the JAVA_HOME path in NiFi's bootstrap.conf to point to the older Java version.

Option 3: Verify Dependencies

Check if you are using the latest versions of NiFi and Apache Lucene:
Some of these warnings may be addressed in recent releases of NiFi or its libraries.
Consider upgrading NiFi to the latest stable version to ensure compatibility with newer Java versions.

Happy hadooping

Re: Getting java warning after staring NiFi

tono425 — Wed, 18 Dec 2024 00:48:18 GMT

@Shelton
Thank you for your advice.

As I use the latest version of NiFi and it requires Java 21, I added the following line in bootstrap.conf and confirmed the warning messages disappeared.

java.arg.EnableNativeAccess=--enable-native-access=ALL-UNNAMED

I appreciate your help.

Thank you,