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Inspiring
August 7, 2026
Question

Start process smart service fails intermittently when running MNI: Failed to start process. Process Model ID: .

  • August 7, 2026
  • 15 replies
  • 71 views

Hi everyone, 

I’m experiencing this odd behaviour with this specific dataset. The other start processes within the platform are running just fine! The log does not provide me any useful info also. 

 

This is my input example. The start process will run in MNI for each set of input. Sometimes parent process stopped because of this error: Failed to start process. Process Model ID: 

ButI open the sub-process it run till the end.

The parent process will run sub-process for each pv!relationshipToUpdate. Process parameters are provided like below: 

Below is my pv!relationshipToUpdate example. 

{

a!map(

fileId: "FILE_GUID_001",

relationshipToRemove: null,

relationshipsToAdd: a!map(

entityId: "ENTITY_001",

entityType: "REFERENCE"

),

approvalNeeded: false,

addRemovalNote: false,

documentDescription: "Sample Document 1.pdf",

updatedRelationships: {

a!map(entityId: "CLIENT_001", entityType: "CLIENT"),

a!map(entityId: "EVENT_001", entityType: "EVENT"),

a!map(entityId: "CASE_001", entityType: "CASE")

}

),

a!map(

fileId: "FILE_GUID_002",

relationshipToRemove: null,

relationshipsToAdd: a!map(

entityId: "ENTITY_001",

entityType: "REFERENCE"

),

approvalNeeded: false,

addRemovalNote: false,

documentDescription: "Sample Document 2.pdf",

updatedRelationships: {

a!map(entityId: "CLIENT_001", entityType: "CLIENT"),

a!map(entityId: "EVENT_001", entityType: "EVENT")

}

)

}

Have anyone seen this issue before? Is it happening to start process with MNI only?

15 replies

stefanhelzle0001
Brainy
August 7, 2026

Did you check the tomcat stdout log file for any details?

linhnAuthor
Inspiring
August 10, 2026

Below is what I got from log. Not really sure what it means by 

InvalidExpressionException: Does not exist: Expression
2026-08-10 06:17:56,219 [Appian Work Item - 1142895 - WorkID 113 - execution02 - process 39915949 - model 13265 : UnattendedJavaActivityRequest] ERROR com.appiancorp.process.engine.UnattendedJavaActivityRequest - An error occurred while executing activity: id=537110329, classname=com.appiancorp.process.runtime.activities.StartProcessSmartService4com.appiancorp.suiteapi.process.exceptions.SmartServiceException: userMsg[error.initiateProcess.userMsg=Failed to start process. Process Model ID: 4071.] alertMsg[error.initiateProcess.alertMsg=Failed to start process. Process Model ID: 4071.]	at com.appiancorp.suiteapi.process.exceptions.SmartServiceException$Builder.build(SmartServiceException.java:139)	at com.appiancorp.process.runtime.utils.SmartServiceExceptionFactory.createException(SmartServiceExceptionFactory.java:14)	at com.appiancorp.process.runtime.activities.StartProcessSmartService4.run(StartProcessSmartService4.java:308)	at com.appiancorp.process.runtime.framework.DefaultActivityExecutor$1.call(DefaultActivityExecutor.java:129)	at com.appiancorp.process.runtime.framework.DefaultActivityExecutor$1.call(DefaultActivityExecutor.java:125)	at com.appiancorp.common.ContextClassLoaderSwitcher.runInContext(ContextClassLoaderSwitcher.java:30)	at com.appiancorp.process.runtime.framework.DefaultActivityExecutor.execute(DefaultActivityExecutor.java:125)	at com.appiancorp.process.engine.UnattendedJavaActivityRequest.execute(UnattendedJavaActivityRequest.java:110)	at com.appiancorp.process.engine.UnattendedJavaActivityRequestResponseCreator.getJavaActivityResultResponse(UnattendedJavaActivityRequestResponseCreator.java:23)	at com.appiancorp.process.engine.UnattendedJavaActivityRequest.getJavaActivityResultResponse(UnattendedJavaActivityRequest.java:89)	at com.appiancorp.process.engine.UnattendedJavaActivityRequest.execute0(UnattendedJavaActivityRequest.java:72)	at com.appiancorp.common.persistence.data.AppianDataUserContextProvider.executeWithConsistentDataReads(AppianDataUserContextProvider.java:106)	at com.appiancorp.process.engine.ProcessContinuationRequest.executeOuter(ProcessContinuationRequest.java:68)	at com.appiancorp.process.engine.ActivityRequest.executeOuter(ActivityRequest.java:41)	at com.appiancorp.process.engine.ContinuationRequest.execute(ContinuationRequest.java:136)	at com.appiancorp.process.engine.UnattendedJavaActivityRequest.execute(UnattendedJavaActivityRequest.java:125)	at com.appiancorp.process.workpoller.UnattendedRequestHandlerBean.onMessage(UnattendedRequestHandlerBean.java:36)	at com.appiancorp.process.workpoller.WorkItem.run(WorkItem.java:110)	at com.appiancorp.common.spring.SimpleTaskWorkManager$DelegatingWorkAdapter.run(SimpleTaskWorkManager.java:227)	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)	at java.base/java.lang.Thread.run(Thread.java:840)Caused by: com.appiancorp.suiteapi.common.exceptions.InvalidExpressionException: Does not exist: Expression	at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)	at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:77)	at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)	at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500)	at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:481)	at com.appiancorp.kougar.mapper.Mapper.prepareThrowable(Mapper.java:171)	at com.appiancorp.kougar.mapper.Mapper.request(Mapper.java:100)	at com.appiancorp.kougar.services.KougarServiceInvocationHandler$KInvocationHandler.invoke(KougarServiceInvocationHandler.java:220)	at com.appiancorp.kougar.services.KougarServiceInvocationHandler.invoke(KougarServiceInvocationHandler.java:367)	at jdk.proxy2/jdk.proxy2.$Proxy633.process(Unknown Source)	at com.appiancorp.process.engine.ProcessEngineServiceImpl$ProcessEngineExecutionServiceImpl.process(ProcessEngineServiceImpl.java:872)	at jdk.internal.reflect.GeneratedMethodAccessor2980.invoke(Unknown Source)	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)	at java.base/java.lang.reflect.Method.invoke(Method.java:569)	at com.appiancorp.util.MethodInvocationReflectionImpl.proceed(MethodInvocationReflectionImpl.java:23)	at com.appiancorp.security.authz.AuthorizationMethodInvocation.invoke0(AuthorizationMethodInvocation.java:63)	at com.appiancorp.security.authz.AuthorizationMethodInterceptor.invoke(AuthorizationMethodInterceptor.java:28)	at com.appiancorp.services.ServiceManager$ServiceInvocationHandler.invoke(ServiceManager.java:479)	at jdk.proxy2/jdk.proxy2.$Proxy633.process(Unknown Source)	at com.appiancorp.process.engine.ProcessEngineServiceImpl.processUnattendedRequest(ProcessEngineServiceImpl.java:216)	at com.appiancorp.process.engine.ProcessEngineServiceImpl.processToNextAttended(ProcessEngineServiceImpl.java:257)	at jdk.internal.reflect.GeneratedMethodAccessor3291.invoke(Unknown Source)	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)	at java.base/java.lang.reflect.Method.invoke(Method.java:569)	at com.appiancorp.util.MethodInvocationReflectionImpl.proceed(MethodInvocationReflectionImpl.java:23)	at com.appiancorp.security.authz.AuthorizationMethodInvocation.invoke0(AuthorizationMethodInvocation.java:63)	at com.appiancorp.security.authz.AuthorizationMethodInterceptor.invoke(AuthorizationMethodInterceptor.java:28)	at com.appiancorp.services.ServiceManager$ServiceInvocationHandler.invoke(ServiceManager.java:479)	at jdk.proxy2/jdk.proxy2.$Proxy632.processToNextAttended(Unknown Source)	at com.appiancorp.process.design.service.ProcessDesignServiceXmlImpl.initiateProcess(ProcessDesignServiceXmlImpl.java:1172)	at com.appiancorp.process.design.service.ExtendedProcessDesignServiceJavaImpl.initiateProcessWithFullResult(ExtendedProcessDesignServiceJavaImpl.java:474)	at jdk.internal.reflect.GeneratedMethodAccessor3289.invoke(Unknown Source)	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)	at java.base/java.lang.reflect.Method.invoke(Method.java:569)	at com.appiancorp.kougar.services.KougarServiceInvocationHandler$JavaInvocationHandler.invoke(KougarServiceInvocationHandler.java:119)	at com.appiancorp.kougar.services.KougarServiceInvocationHandler$KougarMethodInvocation.proceed(KougarServiceInvocationHandler.java:323)	at com.appiancorp.security.authz.AuthorizationMethodInvocation.invoke0(AuthorizationMethodInvocation.java:63)	at com.appiancorp.security.authz.AuthorizationMethodInterceptor.invoke(AuthorizationMethodInterceptor.java:28)	at com.appiancorp.kougar.services.KougarServiceInvocationHandler.invoke(KougarServiceInvocationHandler.java:364)	at jdk.proxy2/jdk.proxy2.$Proxy35.initiateProcessWithFullResult(Unknown Source)	at com.appiancorp.process.runtime.activities.StartProcessSmartService4.run(StartProcessSmartService4.java:263)	... 19 more
kapils024874
Inspiring
August 10, 2026

Can you re-verify all the expression rules which you are calling inside sub-process actually exist?
there might a rule somewhere which exists initially but later on removed by someone which is resulting into your error. 

kapils024874
Inspiring
August 7, 2026

hi ​@linhn ,
I think  it is failing because firing a burst of asynchronous start requests floods the Appian execution engines. The parent node times out waiting for the engine to acknowledge the massive spike in thread requests, which is exactly why the parent throws an error while the sub-processes eventually catch up and finish in the background.

can you try dropping the Start Process smart service completely and replace it with a standard Sub-Process node, which manages multiple instances natively and much more efficiently. Alternatively, and highly recommended, refactor your target process to accept the entire pv!relationshipToUpdate array as a single variable so you can write the data in one batch transaction, eliminating MNI entirely.  
Else you can try removing the activity chaining just the startProcess  which is running in MNI.

Also it is not recommended to use Activity chaining and MNI together.

linhnAuthor
Inspiring
August 10, 2026

Thank you, that does explain my scenario! I will see if there is any other recommendation, else will try refactoring the child process to receive full set of data, as we still prefer using start service for this workflow :)

shubhama926776
Brainy
August 7, 2026

Failed to start process just means the sub-process couldn't be instantiated. Usually an engine load spike from MNI starting all at once, or a null/wrong-type param on specific rows from your index() defaults.

Add onError to log the reason and failing row: if load, batch the starts; if data, ensure every required param is non-null and correctly typed.

https://docs.appian.com/suite/help/26.7/Process_Errors.html

शुभम्
linhnAuthor
Inspiring
August 10, 2026

I have compared the error instance (it actually run to the end successfully but marked as     
Failed to start process within parent process though); and could not find any difference between the Successfully started sub processes and that error one , all inputs are not null.  

harshas2775
Brainy
August 11, 2026

As per your mention in the thread ½ out of 10 instances are affected by this error - It might be a data issue. Can you verify the data in the pv is appropriate to be passed to the subprocess. 

Also, to debug/ as an alternative you can replace MNI with loop around the subprocess. Add counter variables - pv!count and pv!length in process model. Call the subprocess one by one by indexing the main pv using pv!count until it exceeds length value. If process breaks at a point you will know which index/count failed to initiate the sub process and go from there to identify & resolve the issue.

linhnAuthor
Inspiring
August 11, 2026

@harshas2775  When running in loop the parent process completed without any error...

harshas2775
Brainy
August 11, 2026

Good to know!