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    Summon - RCA - February 11, 2020


    This document serves as a Root Cause Analysis for the Summon service interruption experienced by Ex Libris customers on February 11th, 2020

    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: 

    February 11th, 2020 from 1:07 PM until 1:42 PM CST Time.

    During the event the service was unavailable

    Root Cause Analysis

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

    • An upgraded Solr client library introduced with the Solr 7 search engine has different behavior than the older version previously being used.  The new library requires connections to be explicitly closed where this was not required before.  Connections were not being closed properly on a status check call that is made to the system, leading to a slow build up of stuck threads and allocated memory.
    • As threads increased, the search API eventually became unresponsive leading to a system down event.

    Technical Action Items and Preventive Measures

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

    • On the day of the event, traffic was routed to the other data center quickly as it was not experiencing issues.  The second data center was able to hold all load without issue.
    • On February 12, a rolling bounce of the systems was put in place as a short term measure to address the thread buildup.


    • On February 14, a fix for the root thread issue was released.



    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
    February 19, 2020 Initial Publication
    February 25, 2020 Update



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