KB-1685 Appian upgrade results in "403 Forbidden" error on the user interface and "com.appiancorp.kougar.driver.exceptions.Signal: Cannot call itself" error in the application server log

Symptoms

Users intermittently observe a 403 Forbidden error on the interface after performing an Appian upgrade.

The following error is printed in the application server log located at <JBOSS_HOME>\standalone\log\server.log:

[Appian Work Item - 341 - ProcessExec00 : CatchupRequest] ERROR com.appiancorp.process.engine.CatchupRequest - Failed to register catchup (0), can retry
INFO [stdout] (Appian Work Item - 341 - ProcessExec00 : CatchupRequest) com.appiancorp.kougar.driver.exceptions.Signal: Cannot call itself
INFO [stdout] (Appian Work Item - 341 - ProcessExec00 : CatchupRequest) at com.appiancorp.kougar.driver.ipc.IpcConnection.get(IpcConnection.java:390)

The following warning is printed in the db_PX*.log files located at <APPIAN_HOME>\logs\:

[PX011] {pe975.kdb ,1548295} (Default) WARN .a.p.PROCESS.i "Incremental Update: Exec Engine is not ready to start Incremental update.

Cause

The errors indicate that the Appian engine database files did not migrate successfully during the upgrade. One of the likely causes of this issue is an ungraceful shutdown of the Appian engines before the upgrade. 

Action

Revert to the backup that was saved before the upgrade and perform the upgrade again following the Update Guide. Ensure the engines are stopped gracefully on the original environment before performing the upgrade again.

Affected Versions

This article applies to all versions of Appian.