Document new ingest and search pipeline allowlist settings

_ingest-pipelines/processors/index-processors.md

@@ -71,3 +71,7 @@ Processor type | Description
 ## Batch-enabled processors
 
 Some processors support batch ingestion---they can process multiple documents at the same time as a batch. These batch-enabled processors usually provide better performance when using batch processing. For batch processing, use the [Bulk API]({{site.url}}{{site.baseurl}}/api-reference/document-apis/bulk/) and provide a `batch_size` parameter. All batch-enabled processors have a batch mode and a single-document mode. When you ingest documents using the `PUT` method, the processor functions in single-document mode and processes documents in series. Currently, only the `text_embedding` and `sparse_encoding` processors are batch enabled. All other processors process documents one at a time.
+
+## Selectively enabling processors
+
+Processors defined by the [ingest-common module](https://github.com/opensearch-project/OpenSearch/blob/2.x/modules/ingest-common/src/main/java/org/opensearch/ingest/common/IngestCommonPlugin.java) can be selectively enabled by providing the static cluster setting `ingest-common.processors.allowed`. If not specified, then all processors are enabled by default. If an empty list is specified, then all processors are disabled. If the setting is changed to remove previously enabled processors, then any pipeline using a disabled processor will fail after the node is restarted and the new setting takes effect.

_search-plugins/search-pipelines/search-processors.md

@@ -121,3 +121,7 @@ The response contains the `search_pipelines` object that lists the available req
 
 In addition to the processors provided by OpenSearch, additional processors may be provided by plugins.
 {: .note}
+
+## Selectively enabling processors
+
+Processors defined by the [search-pipeline-common module](https://github.com/opensearch-project/OpenSearch/blob/2.x/modules/search-pipeline-common/src/main/java/org/opensearch/search/pipeline/common/SearchPipelineCommonModulePlugin.java) can be selectively enabled by providing the following static cluster settings: `search.pipeline.common.request.processors.allowed`, `search.pipeline.common.response.processors.allowed`, or `search.pipeline.common.search.phase.results.processors.allowed`. If not specified, then all processors are enabled by default. If an empty list is specified, then all processors are disabled. If the setting is changed to remove previously-enabled processors, then any pipeline using a disabled processor will fail after the node is restarted and the new setting takes effect.