Unexpected IndexOrAlias for – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 7.4-7.1

Briefly, this error occurs when Elasticsearch encounters an unexpected index or alias name in a request. This could be due to a typo, a non-existent index/alias, or a naming conflict. To resolve this issue, you can: 1) Check the spelling and case of your index/alias names, 2) Ensure the index/alias exists before making requests, 3) Avoid using special characters in index/alias names, and 4) Ensure unique names to avoid conflicts.

This guide will help you check for common problems that cause the log ” unexpected IndexOrAlias for [{}]: [{}] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: index, alias, plugin.

Log Context

Log “unexpected IndexOrAlias for [{}]: [{}]” classname is SnapshotHistoryStore.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

        } else if (slmHistory.getType() != IndexAbstraction.Type.ALIAS) {
            // This is not an alias; error out
            andThen.onFailure(new IllegalStateException("SLM history alias [" + SLM_HISTORY_ALIAS +
                "] already exists as " + slmHistory.getType().getDisplayName()));
        } else {
            logger.error("unexpected IndexOrAlias for [{}]: [{}]"; SLM_HISTORY_ALIAS; slmHistory);
            // (slmHistory.isAlias() == true) but (slmHistory instanceof Alias == false)?
            assert false : SLM_HISTORY_ALIAS + " cannot be both an alias and not an alias simultaneously";


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