circuit_breaking_exception: CircuitBreakingException[[parent] Data too large, data for [<...>] would be [...], which is larger than the limit of [...]]

What does it mean?

A request was rejected because it would exceed the memory (heap) circuit breaker limit. Elasticsearch stops the request up front to prevent the node from crashing with an OutOfMemoryError. The [parent] breaker guards total memory usage; the [fielddata] breaker guards fielddata memory on text fields.

Why does it happen?

Insufficient JVM heap, very large/complex aggregations, large result sets, large bulk requests, fielddata loaded on text fields, or many heavy concurrent queries filling the heap. It is usually a symptom of heap pressure.

How to fix it

Shrink the queries: reduce aggregation size, bulk batch size and returned fields. Aggregate on the keyword sub-field (.keyword) instead of fielddata on text fields. Increase the JVM heap (~50% of server RAM, at most ~31GB). Monitor heap pressure: GET _cat/nodes?v&h=name,heap.percent. Fix the root cause (memory/query) rather than temporarily raising breaker limits. Check which breaker tripped with GET _nodes/stats/breaker.