Problem:
When two process engines starts in a cluster in parallel, a ProcessEngineException can occur while trying to commit the history level configuration to the database.

org.camunda.bpm.engine.ProcessEngineException: ENGINE-03004 Exception while executing Database Operation 'INSERT PropertyEntity[historyLevel]' with message '#012### Error updating database.
Cause: org.postgresql.util.PSQLException: ERROR: duplicate key value violates unique constraint "act_ge_property_pkey"#012 Detail: Key (name_)=(historyLevel) already exists.

There is no Locking mechanism while setting the history level and this causes the concurrent issue.
org.camunda.bpm.engine.impl.SchemaOperationsProcessEngineBuild#checkHistoryLevel

AT:

• both process engines start successfully

Implementation ideas:

• acquire pessimistic lock before inserting the history level
• perform automatic retry when history level insertion fails with optimistic locking exception or primary key constraint violation