[Pull-based Ingestion] Add all-active ingestion mode documentation

_api-reference/document-apis/pull-based-ingestion-management.md

@@ -315,7 +315,11 @@ response = client.ingestion.get_state(
         "shard": 0,
         "poller_state": "POLLING",
         "error_policy": "DROP",
-        "poller_paused": false
+        "poller_paused": false,
+        "write_block_enabled" : false,
+        "batch_start_pointer" : "KafkaOffset{offset=2}",
+        "is_primary" : true,
+        "node" : "node_name"
       }
     ]
   }

_api-reference/document-apis/pull-based-ingestion.md

@@ -22,12 +22,11 @@ Before using pull-based ingestion, ensure that the following prerequisites are m
 * Install an ingestion plugin for your streaming source using the command `bin/opensearch-plugin install <plugin-name>`. For more information, see [Additional plugins]({{site.url}}{{site.baseurl}}/install-and-configure/additional-plugins/index/). OpenSearch supports the following ingestion plugins: 
   - `ingestion-kafka`
   - `ingestion-kinesis`
-* Enable [segment replication]({{site.url}}{{site.baseurl}}/tuning-your-cluster/availability-and-recovery/segment-replication/index/) with [remote-backed storage]({{site.url}}{{site.baseurl}}/tuning-your-cluster/availability-and-recovery/remote-store/index/). Pull-based ingestion is not compatible with document replication.
 * Configure pull-based ingestion during [index creation](#creating-an-index-for-pull-based-ingestion). You cannot convert an existing push-based index to a pull-based one.
 
 ## Creating an index for pull-based ingestion
 
-To ingest data from a streaming source, first create an index with pull-based ingestion settings. The following request creates an index that pulls data from a Kafka topic:
+To ingest data from a streaming source, first create an index with pull-based ingestion settings. The following request creates an index that pulls data from a Kafka topic in segment replication mode. See [ingestion modes](#ingestion-modes) for other available modes.
 
 ```json
 PUT /my-index
@@ -75,8 +74,25 @@ The `ingestion_source` parameters control how OpenSearch pulls data from the str
 | `poll.timeout` | The maximum time to wait for data in each poll operation. Optional. |
 | `num_processor_threads` | The number of threads for processing ingested data. Optional. Default is 1. |
 | `internal_queue_size` | The size of the internal blocking queue for advanced tuning. Valid values are from 1 to 100,000, inclusive. Optional. Default is 100. |
+| `all_active` | Boolean value determining if all-active ingestion mode should be enabled. This is not supported in segment replication mode. Default value is false. See [ingestion modes](#ingestion-modes) |
 | `param` | Source-specific configuration parameters. Required. <br>&ensp;&#x2022; The `ingest-kafka` plugin requires:<br>&ensp;&ensp;- `topic`: The Kafka topic to consume from<br>&ensp;&ensp;- `bootstrap_servers`: The Kafka server addresses<br>&ensp;&ensp;Optionally, you can provide additional standard Kafka consumer parameters (such as `fetch.min.bytes`). These parameters are passed directly to the Kafka consumer. <br>&ensp;&#x2022; The `ingest-kinesis` plugin requires:<br>&ensp;&ensp;- `stream`: The Kinesis stream name<br>&ensp;&ensp;- `region`: The AWS Region<br>&ensp;&ensp;- `access_key`: The AWS access key<br>&ensp;&ensp;- `secret_key`: The AWS secret key<br>&ensp;&ensp;Optionally, you can provide an `endpoint_override`. | 
 
+
+### Ingestion modes
+
+Pull-based ingestion supports the following modes:
+
+#### Segment replication mode
+
+Pull-based ingestion can be used in the [segment replication]({{site.url}}{{site.baseurl}}/tuning-your-cluster/availability-and-recovery/segment-replication/index/) mode.
+In this mode, the primary shards ingest events from a streaming source and index the documents. Segments are then copied over to the replica shards.
+It is recommended to use this mode with a [remote-backed storage]({{site.url}}{{site.baseurl}}/tuning-your-cluster/availability-and-recovery/remote-store/index/).
+
+#### All-active mode
+
+All-active mode is the document replication equivalent in pull-based ingestion. Primary and replica shards ingest events from the streaming source and index documents independently.
+There is no replication or coordination between the primary and replica shards. Replica shards however may depend on the primary shard during bootstrapping to copy the segment files if a local copy is unavailable.
+
 ### Stream position
 
 When creating an index, you can specify where OpenSearch should start reading from the stream by configuring the `pointer.init.reset` and `pointer.init.reset.value` settings in the `ingestion_source` parameter. OpenSearch will resume reading from the last commited position for existing indexes.