Can t clone index - Common causes and quick fixes

Opster Team

Aug-23, Version: 1-1.1

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Briefly, this error occurs when OpenSearch fails to duplicate an existing index, possibly due to insufficient permissions, lack of disk space, or the index being closed. To resolve this, ensure that the user has the necessary permissions to clone the index. Check if there’s enough disk space available for the operation. If the index is closed, it needs to be opened before cloning. Also, ensure that the index you’re trying to clone is not in the process of being deleted or updated.

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This guide will help you check for common problems that cause the log ” Can’t clone index [ ” to appear. To understand the issues related to this log, read the explanation below about the following OpenSearch concepts: index.

Overview

In OpenSearch, an index (plural: indices) contains a schema and can have one or more shards and replicas. An OpenSearch index is divided into shards and each shard is an instance of a Lucene index.

Indices are used to store the documents in dedicated data structures corresponding to the data type of fields. For example, text fields are stored inside an inverted index whereas numeric and geo fields are stored inside BKD trees.

Examples

Create index

The following example is based on OpenSearch version 5.x onwards. An index with two shards, each having one replica will be created with the name test_index1

PUT /test_index1?pretty
{
    "settings" : {
        "number_of_shards" : 2,
        "number_of_replicas" : 1
    },
    "mappings" : {
        "properties" : {
            "tags" : { "type" : "keyword" },
            "updated_at" : { "type" : "date" }
        }
    }
}

List indices

All the index names and their basic information can be retrieved using the following command:

GET _cat/indices?v

Index a document

Let’s add a document in the index with the command below:

PUT test_index1/_doc/1
{
  "tags": [
    "opster",
    "OpenSearch"
  ],
  "date": "01-01-2020"
}

Query an index

GET test_index1/_search
{
  "query": {
    "match_all": {}
  }
}

Query multiple indices

It is possible to search multiple indices with a single request. If it is a raw HTTP request, index names should be sent in comma-separated format, as shown in the example below, and in the case of a query via a programming language client such as python or Java, index names are to be sent in a list format.

GET test_index1,test_index2/_search

Delete indices

DELETE test_index1

Common problems

It is good practice to define the settings and mapping of an Index wherever possible because if this is not done, OpenSearch tries to automatically guess the data type of fields at the time of indexing. This automatic process may have disadvantages, such as mapping conflicts, duplicate data and incorrect data types being set in the index. If the fields are not known in advance, it’s better to use dynamic index templates.

OpenSearch supports wildcard patterns in Index names, which sometimes aids with querying multiple indices, but can also be very destructive too. For example, It is possible to delete all the indices in a single command using the following commands:

DELETE /*

To disable this, you can add the following lines in the OpenSearch.yml:

action.destructive_requires_name: true

Log Context

Log “Can’t clone index [” class name is SnapshotsService.java. We extracted the following from OpenSearch source code for those seeking an in-depth context :

 final GroupedActionListener> shardCountListener =
 new GroupedActionListener<>(allShardCountsListener; indices.size());
 snapshotInfoListener.whenComplete(snapshotInfo -> {
 for (IndexId indexId : indices) {
 if (RestoreService.failed(snapshotInfo; indexId.getName())) {
 throw new SnapshotException(targetSnapshot; "Can't clone index [" + indexId +
 "] because its snapshot was not successful.");
 }
 }
 // 2. step; load the number of shards we have in each index to be cloned from the index metadata.
 repository.getRepositoryData(ActionListener.wrap(repositoryData -> {

Can t clone index – How to solve this OpenSearch exception

Log Context

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