Failed to set shard index buffer to – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 2.3-2.3

Briefly, this error occurs when Elasticsearch fails to allocate the specified amount of memory for the shard index buffer due to insufficient available memory. This can happen if the buffer size is set too high or if there’s high memory usage in the system. To resolve this issue, you can either increase the available memory on your system or reduce the shard index buffer size in the Elasticsearch settings. Additionally, optimizing your queries and indices can help reduce memory usage.

This guide will help you check for common problems that cause the log ” failed to set shard {} index buffer to [{}] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: index, indexing, indices, memory and shard.

Log Context

Log “failed to set shard {} index buffer to [{}]” classname is
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

             } catch (EngineClosedException e) {
                // ignore
            } catch (FlushNotAllowedEngineException e) {
                // ignore
            } catch (Exception e) {
                logger.warn("failed to set shard {} index buffer to [{}]"; e; shard.shardId(); shardIndexingBufferSize);

    /** check if any shards active status changed; now. */


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