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    Summon - RCA - September 4, 2019


    This document serves as a Root Cause Analysis for the Summon service interruption experienced by Ex Libris customers on September 4th, 2019

    The goal of this document is to share our findings regarding the event, specify the root cause analysis, outline actions to be taken to solve the downtime event, as well as preventive measures Ex Libris is taking to avoid similar cases in future.

    Event Timeline

    Service interruption was experienced by Ex Libris customers served by the Summon instance at the North America Data Center during the following hours: 

    September 4th, 2019 from 6:33 PM until 7:07 PM Pacific Time.

    During the event, the Summon Search API service was online, however, the Summon UI returned an error. The issue was identified almost immediately, and Summon Systems Engineers worked quickly to restore the UI service.


    Root Cause Analysis

    Ex Libris Engineers investigated this event to determine the root cause analysis with the following results:

    Ex Libris Engineers determined that the root cause related to a failure with a ‘feature toggle’ which caused an unhandled exception in the UI. This feature toggle was designed to improve linking optimization and was not a required feature for the maintenance release.

    The feature toggle was disabled and the UI service was restored to normal operation.

    Technical Action Items and Preventive Measures

    Ex Libris has taken the following action and preventive measures to avoid such an occurrence in future:

    • As immediate action, Ex Libris Engineers disabled the ‘feature toggle’ which was causing the unhandled exception for the UI, which restored normal UI service.
    • We have also identified improvements in our testing environment that will ensure scenarios created in this environment better reflect conditions in production and reduce the likelihood of this occurring again.
    • Ex Libris engineers are performing additional extensive testing of the ‘feature toggle’ to prove it out on the full Summon stack prior to its Production use being considered in future.


    Customer Communication

    ExLibris is committed to providing customers with prompt and ongoing updates during Cloud events. Ongoing and prompt updates on service interruptions appear in the system status portal at this address:

    Publication History

    Date Publication History
    September 21, 2019 Initial Publication



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