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KB-XXXX Unable to acquire a Read connection. Safe to retry


The following error in seen in the application server log:

com.appiancorp.kougar.driver.exceptions.SafeRetryException: Unable to acquire a Read connection. Safe to retry.


The error indicates that the application server is unable to communicate with the engines within a reasonable amount of time. This error is often seen when starting up an environment. It can also be seen at other times when the environment is already up and running, but there is a high load on the engines.


If you are running Appian version 17.2 or prior, run the checkengine script: <APPIAN_HOME>/server/_scripts/diagnostic/checkengine.bat|.sh.

If you are running Appian version 17.3 or above, run the status script: <APPIAN_HOME>/services/bin/status.bat|.sh.

I would recommend that you review the performance logs from the time that you encountered the error to see if there was an unusually high load on the system. Based on that information, it may be worthwhile to factor that amount of resource utilization into your application design and/or architecture.

Affected Versions

This article applies to all versions of Appian.

Last Reviewed: December 2017