Adds ZSTD and ZSTD_NO_DICT codecs to core (out of sandbox)

_api-reference/index-apis/create-index.md

@@ -70,30 +70,27 @@ timeout | Time | How long to wait for the request to return. Default is `30s`.
 
 As part of your request, you can supply parameters in your request's body that specify index settings, mappings, and [aliases]({{site.url}}{{site.baseurl}}/opensearch/index-alias/) for your newly created index. The following sections provide more information about index settings and mappings.
 
-
-### Index settings
-
 Index settings are separated into two varieties: static index settings and dynamic index settings. Static index settings are settings that you specify at index creation and can't change later. You can change dynamic settings at any time, including at index creation.
 
-#### Static index settings
+### Static index settings
 
 Setting | Description
 :--- | :---
 index.number_of_shards | The number of primary shards in the index. Default is 1.
 index.number_of_routing_shards | The number of routing shards used to split an index.
 index.shard.check_on_startup | Whether the index's shards should be checked for corruption. Available options are `false` (do not check for corruption), `checksum` (check for physical corruption), and `true` (check for both physical and logical corruption). Default is `false`.
-index.codec | The compression type to use to compress stored data. Available values are `default` (optimizes for retrieval speed) and `best_compression` (optimizes for better compression at the expense of speed, leading to smaller data sizes on disk). For snapshot distributions built with the sandbox feature enabled, `-Dsandbox.enabled=true`, OpenSearch offers a custom-codecs plugin that supports the value `zstd` for Zstandard compression.
 index.routing_partition_size | The number of shards a custom routing value can go to. Routing helps an imbalanced cluster by relocating values to a subset of shards rather than just a single shard. To enable, set this value to greater than 1 but less than `index.number_of_shards`. Default is 1.
 index.soft_deletes.retention_lease.period | The maximum amount of time to retain a shard's history of operations. Default is `12h`.
 index.load_fixed_bitset_filters_eagerly | Whether OpenSearch should pre-load cached filters. Available options are `true` and `false`. Default is `true`.
 index.hidden | Whether the index should be hidden. Hidden indexes are not returned as part of queries that have wildcards. Available options are `true` and `false`. Default is `false`.
 
-#### Dynamic index Settings
+### Dynamic index Settings
 
 Setting | Description
 :--- | :---
 index.number_of_replicas | The number of replica shards each primary shard should have. For example, if you have 4 primary shards and set `index.number_of_replicas` to 3, the index has 12 replica shards. Default is 1.
 index.auto_expand_replicas | Whether the cluster should automatically add replica shards based on the number of data nodes. Specify a lower bound and upper limit (for example, 0-9), or `all` for the upper limit. For example, if you have 5 data nodes and set `index.auto_expand_replicas` to 0-3, then the cluster does not automatically add another replica shard. However, if you set this value to `0-all` and add 2 more nodes for a total of 7, the cluster will expand to now have 6 replica shards. Default is disabled.
+index.codec |  Determines how the index’s stored fields are compressed and stored on the disk. This setting impacts the size of the index shards and the performance of the operations on the index. Available values are: `default', 'best_compression`, `zstd' and `zstd_no_dict`. Two new codecs are introduced in OpenSearch 2.9: `zstd` and `zstd_no_dict`. They provide an option to configure the compression level as an index setting `index.codec.compression_level` which is not available for other codecs. For information about each setting, see [Index codec settomgs](#index-codec-settings).
 index.search.idle.after | Amount of time a shard should wait for a search or get request until it goes idle. Default is `30s`.
 index.refresh_interval | How often the index should refresh, which publishes its most recent changes and makes them available for searching. Can be set to `-1` to disable refreshing. Default is `1s`.
 index.max_result_window | The maximum value of `from` + `size` for searches to the index. `from` is the starting index to search from, and `size` is the amount of results to return. Default: 10000.
@@ -113,4 +110,33 @@ index.routing.allocation.enable | Specifies options for the index’s shard allo
 index.routing.rebalance.enable | Enables shard rebalancing for the index. Available options are `all` (allow rebalancing for all shards), `primaries` (allow rebalancing only for primary shards), `replicas` (allow rebalancing only for replicas), and `none` (do not allow rebalancing). Default is `all`.
 index.gc_deletes | Amount of time to retain a deleted document's version number. Default is `60s`.
 index.default_pipeline | The default ingest node pipeline for the index. If the default pipeline is set and the pipeline does not exist, then index requests fail. The pipeline name `_none` specifies that the index does not have an ingest pipeline.
-index.final_pipeline | The final ingest node pipeline for the index. If the final pipeline is set and the pipeline does not exist, then index requests fail. The pipeline name `_none` specifies that the index does not have an ingest pipeline.
+index.final_pipeline | The final ingest node pipeline for the index. If the final pipeline is set and the pipeline does not exist, then index requests fail. The pipeline name `_none` specifies that the index does not have an ingest pipeline.
+
+### Index codec settings 
+The `index.codec` setting of an OpenSearch index determines how the index’s stored fields are compressed and stored on the disk. It impacts the size of the index shards and the performance of the operations on the index. OpenSearch provides support for four different codecs that can be used for compressing the stored fields. Each codec offers different trade-offs between compression ratio (storage size) and indexing performance (speed). The available codecs are:
+* `default` - This codec employs the `LZ4` algorithm with a preset dictionary, which prioritizes performance over compression ratio. It offers faster indexing and search operations when compared with `best_compression`, but may result in larger index/shard sizes. If no codec is provided in the index settings, then `LZ4`  is used as default algorithm for compression.
+* `best_compression` -  This codec utilizes `zlib` as an underlying algorithm for compression. It achieves high compression ratios resulting in smaller index sizes. However, this may incur additional CPU usage during operations on the index and subsequently may result in high indexing and search latencies. 
+* `zstd` - This codec uses the [`Zstandard` compression algorithm](https://github.com/facebook/zstd), which provides a good balance between compression ratio and speed. It provides significant compression comparable to `best_compression` codec with reasonable CPU usage and improved indexing/search performance comparable to `default` codec.
+* `zstd_no_dict` This codec is similar to `zstd` but excludes the dictionary compression feature. It provides faster indexing and search operations compared to `zstd` at the expense of a slightly larger index size.
+
+`Compression_level` provides a trade-off between compression ratio and speed. Higher compression level results in higher compression ratio (lesser storage size) with a trade off on speed, that is, slower compression and decompression speeds (slower indexing and search latencies). Currently, the `zstd` and `zstd_no_dict`  supports the compression level in the range from 1 to 6. Similar to `index.codec`, `index.codec.compression_level` is an optional index setting. Default compression level 3 is used if an option is not provided.
+
+The setting of an index can be updated using a PUT request. Here's an example using the curl commands to i) close, ii) update the settings and iii) open an index.
+
+# Close the index
+```curl -XPOST "http://localhost:9200/your_index/_close"```
+
+# Update the index.codec setting
+```curl -XPUT "http://localhost:9200/your_index/_settings" -H 'Content-Type: application/json' -d'
+{
+  "index": {
+    "codec": "zstd_no_dict"
+    "codec.compression_level": 3
+  }
+}
+'
+```
+# Reopen the index
+```curl -XPOST "http://localhost:9200/your_index/_open"```
+
+

_install-and-configure/plugins.md

@@ -289,21 +289,6 @@ Members of the OpenSearch community have built countless plugins for the service
 | store-smb | 1.0.0 |
 | transport-nio | 1.0.0 |
 
-### Experimental plugins
-
-OpenSearch offers experimental plugins that may be used in a snapshot distribution that has the [sandbox feature enabled](https://github.com/opensearch-project/OpenSearch/blob/main/sandbox/build.gradle).
-
-| Plugin Name | Description | Earliest Available Version |
-| :--- | :--- |
-| custom-codecs | Provides additional compression codecs. | 1.0.0 |
-
-Use the following example command to enable the sandbox feature:
-
-```bash
-./gradlew assemble -Dsandbox.enabled=true
-bin/opensearch-plugin install file:///path/to/plugin-<version>-SNAPSHOT.zip
-```
-
 ## Related links
 
 - [About Observability]({{site.url}}{{site.baseurl}}/observability-plugin/index/)