OpenSearch/docs/reference/modules/indices/circuit_breaker.asciidoc
Lee Hinman 2be52eff09 Circuit break the number of inline scripts compiled per minute
When compiling many dynamically changing scripts, parameterized
scripts (<https://www.elastic.co/guide/en/elasticsearch/reference/master/modules-scripting-using.html#prefer-params>)
should be preferred. This enforces a limit to the number of scripts that
can be compiled within a minute. A new dynamic setting is added -
`script.max_compilations_per_minute`, which defaults to 15.

If more dynamic scripts are sent, a user will get the following
exception:

```json
{
  "error" : {
    "root_cause" : [
      {
        "type" : "circuit_breaking_exception",
        "reason" : "[script] Too many dynamic script compilations within one minute, max: [15/min]; please use on-disk, indexed, or scripts with parameters instead",
        "bytes_wanted" : 0,
        "bytes_limit" : 0
      }
    ],
    "type" : "search_phase_execution_exception",
    "reason" : "all shards failed",
    "phase" : "query",
    "grouped" : true,
    "failed_shards" : [
      {
        "shard" : 0,
        "index" : "i",
        "node" : "a5V1eXcZRYiIk8lecjZ4Jw",
        "reason" : {
          "type" : "general_script_exception",
          "reason" : "Failed to compile inline script [\"aaaaaaaaaaaaaaaa\"] using lang [painless]",
          "caused_by" : {
            "type" : "circuit_breaking_exception",
            "reason" : "[script] Too many dynamic script compilations within one minute, max: [15/min]; please use on-disk, indexed, or scripts with parameters instead",
            "bytes_wanted" : 0,
            "bytes_limit" : 0
          }
        }
      }
    ],
    "caused_by" : {
      "type" : "general_script_exception",
      "reason" : "Failed to compile inline script [\"aaaaaaaaaaaaaaaa\"] using lang [painless]",
      "caused_by" : {
        "type" : "circuit_breaking_exception",
        "reason" : "[script] Too many dynamic script compilations within one minute, max: [15/min]; please use on-disk, indexed, or scripts with parameters instead",
        "bytes_wanted" : 0,
        "bytes_limit" : 0
      }
    }
  },
  "status" : 500
}
```

This also fixes a bug in `ScriptService` where requests being executed
concurrently on a single node could cause a script to be compiled
multiple times (many in the case of a powerful node with many shards)
due to no synchronization between checking the cache and compiling the
script. There is now synchronization so that a script being compiled
will only be compiled once regardless of the number of concurrent
searches on a node.

Relates to #19396
2016-08-09 10:26:27 -06:00

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[[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_per_minute`::
Limit for the number of unique dynamic scripts within a minute that are
allowed to be compiled. Defaults to 15.