[[circuit-breaker]]
=== Circuit Breaker

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.

These settings can be dynamically updated on a live cluster with the
<<cluster-update-settings,cluster-update-settings>> API.

[[parent-circuit-breaker]]
[float]
==== Parent circuit breaker

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

`indices.breaker.total.limit`::

    Starting limit for overall parent breaker, defaults to 70% of JVM heap.

[[fielddata-circuit-breaker]]
[float]
==== Field data circuit breaker
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:

`indices.breaker.fielddata.limit`::

    Limit for fielddata breaker, defaults to 60% of JVM heap

`indices.breaker.fielddata.overhead`::

    A constant that all field data estimations are multiplied with to determine a
    final estimation. Defaults to 1.03

[[request-circuit-breaker]]
[float]
==== Request circuit breaker

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.

`indices.breaker.request.limit`::

    Limit for request breaker, defaults to 40% of JVM heap

`indices.breaker.request.overhead`::

    A constant that all request estimations are multiplied with to determine a
    final estimation. Defaults to 1