Finished segment upgrade – How to solve this OpenSearch error

Opster Team

Aug-23, Version: 1-2.9

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Briefly, this error occurs when OpenSearch has completed the process of upgrading an index segment. It’s not necessarily an error, but more of an informational message indicating that a segment upgrade operation has been successfully completed. If you’re seeing performance issues, it could be due to the resource-intensive nature of segment upgrades. To resolve this, you can schedule segment upgrades during off-peak hours, ensure your system has adequate resources, or consider optimizing your indices to reduce the number of segments and thus the impact of segment upgrades.

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This guide will help you check for common problems that cause the log ” finished segment upgrade ” to appear. To understand the issues related to this log, read the explanation below about the following OpenSearch concepts: index, upgrade.

Log Context

Log “finished segment upgrade” classname is
We extracted the following from OpenSearch source code for those seeking an in-depth context :

                if (flush) {
                    flush(false; true);
                if (upgrade) {
          "finished segment upgrade");
            } finally {
        } catch (AlreadyClosedException ex) {


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