Failed to read index file – How to solve related issues

Opster Team

Jan-20, Version: 1.7-8.0

Before you begin reading this guide, we recommend you run Elasticsearch Error Check-Up which analyzes 2 JSON files to detect many errors.

Briefly, this error occurs when Elasticsearch is unable to read a specific index file. This may occur if the file is corrupted or if the storage device hosting the file is damaged. To resolve this error, you can try the following steps: (1) Check the storage device hosting the index file and ensure that it is functioning correctly. (2) Use Elasticsearch’s built-in recovery mechanisms to recover data from backup copies. (3) Delete the affected index and create a new one with the same name.

To easily locate the root cause and resolve this issue try AutoOps for Elasticsearch & OpenSearch. It diagnoses problems by analyzing hundreds of metrics collected by a lightweight agent and offers guidance for resolving them.

This guide will help you check for common problems that cause the log ” Failed to read index file ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: blobstore, discovery-file, index, repositories and repository-azure.

Log Context

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

                     final BlobStoreIndexShardSnapshots shardSnapshots =
              ; Integer.toString(latest));
                    return new Tuple(shardSnapshots; latest);
                } catch (IOException e) {
                    final String file = SNAPSHOT_INDEX_PREFIX + latest;
                    logger.warn(() -> new ParameterizedMessage("failed to read index file [{}]"; file); e);
            } else if (blobKeys.isEmpty() == false) {
                logger.warn("Could not find a readable index-N file in a non-empty shard snapshot directory [{}]"; blobContainer.path());


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