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


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


This error is often seen when starting up an environment. However, it can also be seen at other times when the environment is already up and running. 

This error indicates your app server is unable to communicate with the engines. 

This likely indicates that an Appian engine was too busy to handle the original request from the app server within a reasonable amount of time. As the error indicated, the request was safe to retry. So, as expected, once the necessary resources were freed up, and you retried, the request completed successfully. 


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