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At least once of the following messages in seen in the application server log:
com.appiancorp.kougar.driver.exceptions.SafeRetryException: Unable to acquire a Read connection. Safe to retry.
com.appiancorp.kougar.driver.exceptions.SafeRetryException: Unable to acquire a Write connection. Safe to retry.
This message indicates that a particular engine received a request to do something, but did not receive a response within an acceptable time frame. 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 system. Any of the following are reasons why this message could be seen in the logs:
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.
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.
If there is an issue with any of the engines, work to resolve the issues based on the documentation.
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 system is busy processing work. The request will be retried again 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
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