[NIFI-7923] Nar Auto-Loader cannot recover from Throwable/Error

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.12.0
• Fix Version/s: 1.13.0
• Component/s: Extensions
• Assignee: Bryan Bende
• Reporter: Nick Lawrence
• Created: 14/Oct/20 15:19
• Updated: 27/Oct/20 16:34
• Resolved: 27/Oct/20 16:34

Description

When a nar is built against an up-level JVM, a java Error is thrown while loading the nar extension. The Throwable is not handled as the code only handles sub classes of Exception. As a result the thread dies, and when a corrected nar is later installed, the nar cannot be loaded. Restart of nifi causes the updated nar to be loaded.

2020-10-14 13:31:55,340 INFO [NAR Auto-Loader] -> org.apache.nifi.nar.NarClassLoaders -> Loaded NAR file: /opt/nifi/./work/nar/extensions/nifi-hri-nar-1.0-SNAPSHOT.nar-unpacked as class loader org.apache.nifi.nar.NarClassLoader[./work/nar/extensions/nifi-hri-nar-1.0-SNAPSHOT.nar-unpacked]
2020-10-14 13:31:55,342 INFO [NAR Auto-Loader] -> org.apache.nifi.nar.StandardNarLoader -> Successfully created class loaders for 1 NARs, 0 were skipped
2020-10-14 13:31:55,395 ERROR [NAR Auto-Loader] -> org.apache.nifi.NiFi -> An Unknown Error Occurred in Thread Thread[NAR Auto-Loader,5,main]: java.lang.UnsupportedClassVersionError: com/ibm/watson/health/wffh/nifi/processors/hri/GetHriIngestRecords has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0
2020-10-14 13:31:55,396 ERROR [NAR Auto-Loader] -> org.apache.nifi.NiFi ->
java.lang.UnsupportedClassVersionError: com/ibm/watson/health/wffh/nifi/processors/hri/GetHriIngestRecords has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:756)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:468)
at java.net.URLClassLoader.access$100(URLClassLoader.java:74)
at java.net.URLClassLoader$1.run(URLClassLoader.java:369)
at java.net.URLClassLoader$1.run(URLClassLoader.java:363)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:362)
at java.lang.ClassLoader.loadClass(ClassLoader.java:418)
at java.lang.ClassLoader.loadClass(ClassLoader.java:351)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:348)
at java.util.ServiceLoader$LazyIterator.nextService(ServiceLoader.java:370)
at java.util.ServiceLoader$LazyIterator.next(ServiceLoader.java:404)
at java.util.ServiceLoader$1.next(ServiceLoader.java:480)
at org.apache.nifi.nar.StandardExtensionDiscoveringManager.loadExtensions(StandardExtensionDiscoveringManager.java:156)
at org.apache.nifi.nar.StandardExtensionDiscoveringManager.discoverExtensions(StandardExtensionDiscoveringManager.java:131)
at org.apache.nifi.nar.StandardNarLoader.load(StandardNarLoader.java:110)
at org.apache.nifi.nar.NarAutoLoaderTask.run(NarAutoLoaderTask.java:128)
at java.lang.Thread.run(Thread.java:748)

I looked at the source enough to believe that the Error is not handled anywhere between StandardExtensionDiscovingManager.loadExtensions and NarAutoLoaderTask.run.

I see no messages in the log that suggest that the updated nar is processed after it is placed in the extensions directory.

Issue Links

• links to: GitHub Pull Request #4623