topic Re: Unique contraint violated - ACT_HI_VARINST(ID_) in Alfresco Archive

Unique contraint violated - ACT_HI_VARINST(ID_)

badrisudheer — Mon, 28 Jan 2013 16:00:23 GMT

When we have activiti engine running in 2 different servers (trying to setup a clustered environment) pointing to same DB schema. one of the engines is throwing java.sql.SQLIntegrityConstraintViolationException: ORA-00001: unique constraint (APP.SYS_C00386332) violated. This is violating unique cons

Re: Unique contraint violated - ACT_HI_VARINST(ID_)

ronald_van_kuij — Mon, 28 Jan 2013 19:30:26 GMT

By default Activiti does use a kind of sequence with batches to get ID blocks, but in a db independent way… That two servers get the same block sounds kind of strange and I never heard something like this before.

Isn't there by accident old data in the database and the 'sequence' is reset by accident?

Re: Unique contraint violated - ACT_HI_VARINST(ID_)

frederikherema1 — Tue, 29 Jan 2013 09:14:36 GMT

There is a property in the ACT_GE_PROPERTY, containing the start of the next "block" of ID's to use, if you're using the default ID-generation strategy. This mechanism will make sure a single engine will use a block of ID's without conflicts, having only one thread allocating a new block. When multiple engines are using the same DB, and they (under heavy load) both fetch a new block at the same time, they will both try to update the 'next.dbid' property in ACT_GE_PROPERTY, one of them should get an ActivitiOptimisticLockException.

If you have duplicate id's, this means this mechanism didn't work as expected, which sounds strange.Can you check if it's a whole block of ID's that are duplicate? Or just a few randomly distributed?

You could also use the StrongUUIDGenerator as id-generator, instead of the DB-approach:


/**
 * {@link IdGenerator} implementation based on the current time and the ethernet
 * address of the machine it is running on.
 * 
 * @author Daniel Meyer
 */
public class StrongUuidGenerator implements IdGenerator {

Re: Unique contraint violated - ACT_HI_VARINST(ID_)

badrisudheer — Tue, 29 Jan 2013 22:55:33 GMT

By default Activiti does use a kind of sequence with batches to get ID blocks, but in a db independent way… That two servers get the same block sounds kind of strange and I never heard something like this before.

Isn't there by accident old data in the database and the 'sequence' is reset by accident?

We have configured activiti.database.update=true in that environment. So, I hope the old data does stay in ACT_ tables when we do Upgrade of Activiti version and every time we deploy the application. But, I did not understand what do you mean by 'sequence' reset, how can I verify that?

Re: Unique contraint violated - ACT_HI_VARINST(ID_)

badrisudheer — Tue, 29 Jan 2013 23:11:34 GMT

There is a property in the ACT_GE_PROPERTY, containing the start of the next "block" of ID's to use, if you're using the default ID-generation strategy. This mechanism will make sure a single engine will use a block of ID's without conflicts, having only one thread allocating a new block. When multiple engines are using the same DB, and they (under heavy load) both fetch a new block at the same time, they will both try to update the 'next.dbid' property in ACT_GE_PROPERTY, one of them should get an ActivitiOptimisticLockException.

If you have duplicate id's, this means this mechanism didn't work as expected, which sounds strange.Can you check if it's a whole block of ID's that are duplicate? Or just a few randomly distributed?

You could also use the StrongUUIDGenerator as id-generator, instead of the DB-approach:

/** * {@link IdGenerator} implementation based on the current time and the ethernet * address of the machine it is running on. * * @author Daniel Meyer */ public class StrongUuidGenerator implements IdGenerator {

I did observe ActivitiOptimisticLockException errors in some cases but, in other cases I was seeing Unique constraint violation errors. The big problem is when this happens the workflow for which the exception was thrown gets hung. I do see the 'next.dbid' property in ACT_GE_PROPERTY getting updated. So, It looks like we are using DB-approach. Is StrongUUIDGenerator provided by Activiti framework. If so, How do I set activiti to use StrongUUIDGenerator?

Edit: I did see StrongUuidGenerator under org.activiti.engine.impl.persistence package. Is it thread safe? and how do I set Activiti use StrongUuidGenerator instead of DB-approach?

Re: Unique contraint violated - ACT_HI_VARINST(ID_)

ronald_van_kuij — Wed, 30 Jan 2013 07:25:46 GMT

Is it thread safe?

Search the internet: http://bit.ly/WAnszH (read the whole topic)

and how do I set Activiti use StrongUuidGenerator instead of DB-approach?

Search the internet: http://bit.ly/116NtOz (hint: read e.g. the ACT-789 at the end)