FailEngine threw exception – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 6.8-8.9

Briefly, this error occurs when Elasticsearch encounters a severe internal problem with its search or indexing engine, causing it to fail. This could be due to issues like disk space running out, corruption in the index, or hardware failure. To resolve this, you can try freeing up disk space, checking for hardware issues, or rebuilding the corrupted index. If the problem persists, consider increasing the Elasticsearch heap size or reviewing your cluster’s health and logs for more specific issues.

This guide will help you check for common problems that cause the log ” failEngine threw exception ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: index.

Log Context

Log “failEngine threw exception” classname is
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

                    eventListener.onFailedEngine(reason; failure);
            } catch (Exception inner) {
                if (failure != null) inner.addSuppressed(failure);
                // don't bubble up these exceptions up
                logger.warn("failEngine threw exception"; inner);
        } else {
                () -> format("tried to fail engine but could not acquire lock - engine should be failed by now [%s]"; reason);