What is the main cause of the warning “x of y shards failed” in Kibana?
This warning comes when field data is not present in x number of index of Txnstore. So, Kibana will show a visualization/dashboard just for (y-x) index’s data.
Refer to Knowledge Base for more information - Kibana Reporting
Reason for this worning - when you have old index data in Txnstore. After that you are adding new fields, creating reports using that field and you forgot to add mappings for that new field in old indexes.
In ElasticSearch an index can store a large amount of data that can exceed the hardware limits of a single node. Elasticsearch provides the ability to subdivide your index into multiple pieces called shards. When you create an index, you can define the number of shards that you want. Documents are stored in shards, and shards are allocated to nodes in your cluster.
There can be n number of reason why a shard failed to load. Sometimes may be due to n/w issue, hardware space issue, data aggregation issue or Field Type Conflict
You can inspect the browser requests and find the actual rca.