[[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 60% of JVM heap

`indices.breaker.request.overhead`::

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

[[in-flight-circuit-breaker]]
[float]
==== In flight requests circuit breaker

The in flight requests circuit breaker allows Elasticsearch to limit the memory usage of all
currently active incoming requests on transport or HTTP level from exceeding a certain amount of
memory on a node. The memory usage is based on the content length of the request itself.

`network.breaker.inflight_requests.limit`::

    Limit for in flight requests breaker, defaults to 100% of JVM heap. This means that it is bound
    by the limit configured for the parent circuit breaker.

`network.breaker.inflight_requests.overhead`::

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

[[script-compilation-circuit-breaker]]
[float]
==== Script compilation circuit breaker

Slightly different than the previous memory-based circuit breaker, the script
compilation circuit breaker limits the number of inline script compilations
within a period of time.

See the "prefer-parameters" section of the <<modules-scripting-using,scripting>>
documentation for more information.

`script.max_compilations_rate`::

    Limit for the number of unique dynamic scripts within a certain interval
    that are allowed to be compiled. Defaults to 75/5m, meaning 75 every 5 
    minutes.