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Briefly, this error occurs when there’s a conflict between the primary term of a shard and the cluster state. The primary term is a counter that increases each time a new primary shard is assigned. If a shard has a higher primary term than the cluster state, it’s deleted to prevent stale or duplicate data. To resolve this, you can try to manually increase the primary term of the cluster state, or restart the node to force a new primary shard assignment. Also, ensure your OpenSearch version is up-to-date as this could be a bug fixed in later versions.
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This guide will help you check for common problems that cause the log ” Deleted primary term {} ” to appear. To understand the issues related to this log, read the explanation below about the following OpenSearch concepts: index.
Quick links
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 “Deleted primary term {}” classname is TranslogTransferManager.java.
We extracted the following from OpenSearch source code for those seeking an in-depth context :
ThreadPool.Names.REMOTE_PURGE;
remoteDataTransferPath.add(String.valueOf(primaryTerm));
new ActionListener() {
@Override
public void onResponse(Void unused) {
logger.info("Deleted primary term {}"; primaryTerm);
}
@Override
public void onFailure(Exception e) {
logger.error(new ParameterizedMessage("Exception occurred while deleting primary term {}"; primaryTerm); e);
