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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/the engines are busy processing work.
If you are running Appian version 17.2 or prior, run the checkengine script to diagnose any potential engine related issues: <APPIAN_HOME>/server/_scripts/diagnostic/checkengine.bat|.sh.
<APPIAN_HOME>/server/_scripts/diagnostic/checkengine.bat|.sh
If you are running Appian version 17.3 or above, run the status script to diagnose any potential engine related issues: <APPIAN_HOME>/services/bin/status.bat|.sh.
<APPIAN_HOME>/services/bin/status.bat|.sh
If the engines are up and running without any issues, the error message is simply indicating that the particular request could not be handled at the time because the engines are busy processing work and will be retried later once resources are freed up. Review the performance logs from the time that the error was encountered to see if there was an unusually high load on the system.
This article applies to all versions of Appian.
Last Reviewed: December 2017