Briefly, this error occurs when Elasticsearch is unable to retrieve or parse the metadata for a specific index or document. This could be due to a corrupted index, incorrect permissions, or a network issue. To resolve this, you can try to restore the index from a backup, check and correct the permissions, or investigate network connectivity. If the index is corrupted and there’s no backup, you may need to reindex the data.
This guide will help you check for common problems that cause the log ” failed to get/parse _meta for [{}] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: routing.
Overview
In Elasticsearch, routing refers to document routing. When you index a document, Elasticsearch will determine which shard the document should be routed to for indexing.
The shard is selected based on the following formula:
shard = hash(_routing) % number_of_primary_shards
Where the default value of _routing is _id.
It is important to know which shard the document is routed to, because Elasticsearch will need to determine where to find that document later on for document retrieval requests.
Examples
In twitter index with 2 primary shards, the document with _id equal to “440” gets routed to the shard number:
shard = hash( 440 ) % 2
PUT twitter/_doc/440
{
...
}Notes and good things to know
- In order to improve search speed, you can create custom routing. For example, you can enable custom routing that will ensure that only a single shard will be queried (the shard that contains your data).
- To create custom routing in Elasticsearch, you will need to configure and define that not all routing will be completed by default settings. ( v <= 5.0)
PUT my_index/customer/_mapping
{
"order":{
"_routing":{
"required":true
}
}
}- This will ensure that every document in the “customer” type must specify a custom routing. For Elasticsearch version 6 or above you will need to update the same mapping as:
PUT my_index/_mapping
{
"order":{
"_routing":{
"required":true
}
}
}Log Context
Log “failed to get/parse _meta for [{}]” classname is RiversRouter.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :
} catch (IndexMissingException e) {
// ignore; we will get it next time
} catch (IllegalIndexShardStateException e) {
// ignore; we will get it next time
} catch (Exception e) {
logger.warn("failed to get/parse _meta for [{}]"; e; mappingType);
}
}
}
// At least one type does not have _meta; so we are
