Unable to create snapshot from vm snapshot

[ravening]

Description

When tried to create snapshot from vm snapshot, we get NPE

Steps to reproduce

1. create a vm
2. Create vm snapshot
3. Try to create snapshot from vm snapshot

2020-10-27 12:48:29,466 INFO  [o.a.c.a.c.u.s.CreateSnapshotFromVMSnapshotCmd] (API-Job-Executor-2:ctx-b56cf1c3 job-38 ctx-3b69b2d1) (logid:00211b32) CreateSnapshotFromVMSnapshotCmd with vm snapshot id:2 and snapshot id:1 starts:1603802909463
2020-10-27 12:48:29,507 DEBUG [o.a.c.a.c.u.s.CreateSnapshotFromVMSnapshotCmd] (API-Job-Executor-2:ctx-b56cf1c3 job-38 ctx-3b69b2d1) (logid:00211b32) Failed to create snapshot
java.lang.NullPointerException
        at com.cloud.storage.snapshot.SnapshotManagerImpl.backupSnapshotFromVmSnapshot(SnapshotManagerImpl.java:469)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.base/java.lang.reflect.Method.invoke(Method.java:564)
        at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:344)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:198)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163)
        at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:95)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
        at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212)
        at com.sun.proxy.$Proxy208.backupSnapshotFromVmSnapshot(Unknown Source)
        at org.apache.cloudstack.api.command.user.snapshot.CreateSnapshotFromVMSnapshotCmd.execute(CreateSnapshotFromVMSnapshotCmd.java:179)
        at com.cloud.api.ApiDispatcher.dispatch(ApiDispatcher.java:156)
        at com.cloud.api.ApiAsyncJobDispatcher.runJob(ApiAsyncJobDispatcher.java:108)
        at org.apache.cloudstack.framework.jobs.impl.AsyncJobManagerImpl$5.runInContext(AsyncJobManagerImpl.java:620)
        at org.apache.cloudstack.managed.context.ManagedContextRunnable$1.run(ManagedContextRunnable.java:48)
        at org.apache.cloudstack.managed.context.impl.DefaultManagedContext$1.call(DefaultManagedContext.java:55)
        at org.apache.cloudstack.managed.context.impl.DefaultManagedContext.callWithContext(DefaultManagedContext.java:102)
        at org.apache.cloudstack.managed.context.impl.DefaultManagedContext.runWithContext(DefaultManagedContext.java:52)
        at org.apache.cloudstack.managed.context.ManagedContextRunnable.run(ManagedContextRunnable.java:45)
        at org.apache.cloudstack.framework.jobs.impl.AsyncJobManagerImpl$5.run(AsyncJobManagerImpl.java:568)
        at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
        at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
        at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
        at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630)
        at java.base/java.lang.Thread.run(Thread.java:832)

Types of changes

• Bug fix (non-breaking change which fixes an issue)

[DaanHoogland]

@ravening , how do you want to create a snapshot from a snaopshot; do you go through the snapshot -> template -> vm --> snapshot cycle?

[ravening]

@ravening , how do you want to create a snapshot from a snaopshot; do you go through the snapshot -> template -> vm --> snapshot cycle?

@DaanHoogland No

1. Instances -> select any running vm -> create vm snapshot
2. Navigate to VM snapshot ->select the above create vm snapshot -> create snapshot from vm snapshot

[harikrishna-patnala]

Code related to fix the NPE looks good to me. This issue exists on master as well.

[DaanHoogland]

@harikrishna-patnala we merge to master when it is on 4.14 so the fix will automatically get there.

[DaanHoogland]

code looks good indeed, let's find some test that proves it (for future guarding as well as merge justification)
@blueorangutan package

[blueorangutan]

@DaanHoogland a Jenkins job has been kicked to build packages. I'll keep you posted as I make progress.

[blueorangutan]

Packaging result: ✔centos7 ✖centos8 ✔debian. JID-2291

[DaanHoogland]

@blueorangutan test

[blueorangutan]

@DaanHoogland a Trillian-Jenkins test job (centos7 mgmt + kvm-centos7) has been kicked to run smoke tests

[blueorangutan]

Trillian test result (tid-3095)
Environment: kvm-centos7 (x2), Advanced Networking with Mgmt server 7
Total time taken: 32605 seconds
Marvin logs: https://github.com/blueorangutan/acs-prs/releases/download/trillian/pr4432-t3095-kvm-centos7.zip
Intermittent failure detected: /marvin/tests/smoke/test_hostha_kvm.py
Smoke tests completed. 83 look OK, 0 have error(s)
Only failed tests results shown below:

Test	Result	Time (s)	Test File