Field data

The field data cache is used mainly when sorting on or faceting on a field. It loads all the field values to memory in order to provide fast document based access to those values. The field data cache can be expensive to build for a field, so its recommended to have enough memory to allocate it, and to keep it loaded.

The amount of memory used for the field data cache can be controlled using indices.fielddata.cache.size. Note: reloading the field data which does not fit into your cache will be expensive and perform poorly.

Elasticsearch contains multiple circuit breakers used to prevent operations from causing an OutOfMemoryError. Each breaker specifies a limit for how much memory it can use. Additionally, there is a parent-level breaker that specifies the total amount of memory that can be used across all breakers.

The parent-level breaker can be configured with the following setting:

All circuit breaker settings can be changed dynamically using the cluster update settings API.

The field data circuit breaker allows Elasticsearch to estimate the amount of memory a field will require to be loaded into memory. It can then prevent the field data loading by raising an exception. By default the limit is configured to 60% of the maximum JVM heap. It can be configured with the following parameters:

The request circuit breaker allows Elasticsearch to prevent per-request data structures (for example, memory used for calculating aggregations during a request) from exceeding a certain amount of memory.

You can monitor memory usage for field data as well as the field data circuit breaker using Nodes Stats API