Briefly, this error occurs when there’s a conflict between the existing index and a new one that Elasticsearch is trying to create. This could be due to a naming conflict or a conflict in the index settings. To resolve this issue, you can either rename the new index, delete the existing index if it’s no longer needed, or adjust the settings of the new index to avoid the conflict. Additionally, ensure that your indexing operations are properly sequenced to avoid such conflicts in the future.
This log could be avoided if detected earlier. Before you read this guide, we recommend you run the Elasticsearch Error Check-Up which detects issues in ES that cause log errors. The Check-Up includes checks that would help you prevent the drop of an index due to conflict with a tribe node. It’s a free tool that requires no installation and takes 2 minutes to complete. You can run the Check-Up here. Â
This guide will help you understand common problems that cause the log “Dropping index due to conflict with” to appear. It’s important to be familiar with the issues related to the log, so to get started, read the general overview on common issues and tips related to the relevant Elasticsearch concepts: index and tribe.
Quick Overview
This error arises when:
- Tribe nodes are used to search across multiple clusters,
- An index with the same name exists in multiple clusters, and
- The value tribe.on_conflict the setting is to drop.
Why this Log AppearsÂ
Tribe nodes used to act as a client for searching across multiple clusters, but they were deprecated in Elasticsearch version 5.4 in favor of a cross-cluster search feature. The tribe node retrieves the state of all the connected clusters and merges them in a common global state. It performs read and write operations to all the clusters while they’re in a local state. This feature raises a limitation as well. In a single cluster state, the name of each index must be unique. If there are duplicate index names, then the tribe node by default selects only one index unless its behavior is modified to drop, in which case it drops the index altogether.
Impact and Effect
This log means that an index is dropped from the state of the local state of the tribe node and hence stops being searchable.
How to Fix and PreventÂ
- Use tribe.on_conflict setting to let the tribe node know what to do when there is an index name conflict across multiple clusters. The default value of this setting is set to any, but can also be set to prefer_[tribeName].
- Consider upgrading to at least Elasticsearch version 5.4 or above with the cross-cluster-search feature instead of tribe nodes. This feature allows you to search indices with the same name inside different clusters without any conflict.
Overview
In Elasticsearch, an index (plural: indices) contains 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 the command below:
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 “[{}] dropping index {} due to conflict with [{}]” classname is TribeService.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :
if (ON_CONFLICT_ANY.equals(onConflict)) {
// we chose any tribe; carry on
} else if (ON_CONFLICT_DROP.equals(onConflict)) {
// drop the indices; there is a conflict
clusterStateChanged = true;
logger.info("[{}] dropping index {} due to conflict with [{}]"; tribeName; tribeIndex.getIndex();
existingFromTribe);
removeIndex(blocks; metaData; routingTable; tribeIndex);
droppedIndices.add(indexName);
} else if (onConflict.startsWith(ON_CONFLICT_PREFER)) {
// on conflict; prefer a tribe...
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