NPE when try to kill linux process running JDK8

[agliznetsov]

java.lang.RuntimeException: Could not kill process id 5267
at com.jezhumble.javasysmon.LinuxMonitor.killProcess(LinuxMonitor.java:156)
at com.jezhumble.javasysmon.JavaSysMon.killProcess(JavaSysMon.java:242)
...
Caused by: java.lang.NullPointerException
at com.jezhumble.javasysmon.LinuxMonitor.killProcess(LinuxMonitor.java:154)
... 7 more

[csemrau]

We just stumbled over this bug in version 0.3.3. Looking at the sources, I expect it can still be found in 0.3.5.
What should one do now?

[rich-coe]

What JVM are you running?
One way I see this to occur is that there isn't a declaration in the JVM for java.lang.UNIXProcess.destroyProcess(int) which javasysmon is trying to invoke.

[csemrau]

We are using the following:

/etc/alternatives/java_sdk_1.8.0/bin/java -version
openjdk version "1.8.0_65"
OpenJDK Runtime Environment (build 1.8.0_65-b17)
OpenJDK 64-Bit Server VM (build 25.65-b01, mixed mode)

I also suspect that that method does not exist in the runtime we are using. There is a javasysmon fork from atlassian, which seems to fix this issue, by executing a kill command instead. Will check that out soon.

[rich-coe]

I ran this simple groovy program on oracle jdk-1.8 and jre-1.8.0-openjdk and it fails like your report
on openjdk. The trick in the javasysmon code only works on oracle java.

def dmeth = null
def csig = new Class[1]
csig[0] = int.class

try {
    Class clazz = Class.forName("java.lang.UNIXProcess");
    dmeth = clazz.getDeclaredMethod("destroyProcess", csig)
    dmeth.setAccessible(true);
 } catch (Exception ex) {
     println "exception ${ex}"
     ex.printStackTrace()
 }

error message from openjdk

 exception java.lang.NoSuchMethodException: java.lang.UNIXProcess.destroyProcess(int)
 java.lang.NoSuchMethodException: java.lang.UNIXProcess.destroyProcess(int)
    at java.lang.Class.getDeclaredMethod(Class.java:2130)
    at java_lang_Class$getDeclaredMethod.call(Unknown Source)
    at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:45)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:108)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:120)
    at dtest.run(dtest.groovy:8)
    [...]

[danielflower]

Java 8 has added Process.destroyForcibly() which does what the above code tries to do, but using a public API instead of trying to execute private methods. But, this library is supposed to support Java 1.4+, so maybe the fix is to try to first find a paramaterless method called destroyForcibly (still using reflection) and fall back to the above code for Java 7 and earlier?