Can not be imported as a dangling index; as index with same name already exists in cluster metadata – Elasticsearch Log Diagnostic

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Log Context – usefull for experts
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Troubleshooting background

To troubleshoot Elasticsearch log “Can not be imported as a dangling index; as index with same name already exists in cluster metadata” it’s important to know common problems related to Elasticsearch concepts: cluster, dangling, index, indices, metadata. See below-detailed explanations complete with common problems, examples and useful tips.

Cluster in Elasticsearch

What is it

In Elasticsearch a cluster is a collection of one or more nodes (servers / VMs). A cluster can consist of an unlimited number of nodes. The cluster provides interface for indexing and storing data and search capability across all of the data which is stored in the data nodes

Each cluster has a single master node that is elected by the master eligible nodes. In cases where the master is not available the other connected master eligible nodes elect a new master. Clusters are identified by a unique name, which defaults to “Elasticsearch”.

Index in Elasticsearch

What it is

In Elasticsearch, an index (indices in plural) can be thought of as a table inside a database that has a schema and can have one or more shards and replicas. An Elasticsearch 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 Elasticsearch 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 below command:

PUT test_index1/_doc/1
{
  "tags": [
    "opster",
    "elasticsearch"
  ],
  "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, Elasticsearch 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.
  • Elasticsearch 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 elasticsearch.yml:

action.destructive_requires_name: true


Log Context

Log ”Can not be imported as a dangling index; as index with same name already exists in cluster metadata” classname is DanglingIndicesState.java
To help get the right context about this log, we have extracted the following from Elasticsearch source code

<pre class="wp-block-syntaxhighlighter-code">             final List<IndexMetaData> indexMetaDataList = metaStateService.loadIndicesStates(excludeIndexPathIds::contains);
            Map<Index; IndexMetaData> newIndices = new HashMap<>(indexMetaDataList.size());
            final IndexGraveyard graveyard = metaData.indexGraveyard();
            for (IndexMetaData indexMetaData : indexMetaDataList) {
                if (metaData.hasIndex(indexMetaData.getIndex().getName())) {
                    logger.warn("[{}] can not be imported as a dangling index; as index with same name already exists in cluster metadata";
                        indexMetaData.getIndex());
                } else if (graveyard.containsIndex(indexMetaData.getIndex())) {
                    logger.warn("[{}] can not be imported as a dangling index; as an index with the same name and UUID exist in the " +
                                "index tombstones.  This situation is likely caused by copying over the data directory for an index " +
                                "that was previously deleted."; indexMetaData.getIndex());




</pre>

To help troubleshoot related issues we have gathered selected answers from STOF & Discuss and issues from Github, please review the following for further information :

How To Resolve Dangling Indices Err
discuss.elastic.co/t/how-to-resolve-dangling-indices-error-on-each-index/130609

 

Can Not Be Imported As A Dangling I
discuss.elastic.co/t/can-not-be-imported-as-a-dangling-index-as-index-with-same-name-already-exists-in-cluster-metadata/89455

 


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