Update tiered cache documentation (#6817)

* Update tiered cache documentation Signed-off-by: Fanit Kolchina <[email protected]> * Remove comma Signed-off-by: Fanit Kolchina <[email protected]> * Update _search-plugins/caching/tiered-cache.md Co-authored-by: Nathan Bower <[email protected]> Signed-off-by: kolchfa-aws <[email protected]> * Editorial comments Signed-off-by: Fanit Kolchina <[email protected]> --------- Signed-off-by: Fanit Kolchina <[email protected]> Signed-off-by: kolchfa-aws <[email protected]> Co-authored-by: Nathan Bower <[email protected]>
opensearch-project · Apr 1, 2024 · 3ee76bb · 3ee76bb
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diff --git a/_search-plugins/caching/tiered-cache.md b/_search-plugins/caching/tiered-cache.md
@@ -11,11 +11,11 @@ nav_order: 10
 This is an experimental feature and is not recommended for use in a production environment. For updates on the progress of the feature or if you want to leave feedback, see the associated [GitHub issue](https://github.com/opensearch-project/OpenSearch/issues/10024).    
 {: .warning}
 
-A tiered cache is a multi-level cache, in which each tier has its own characteristics and performance levels. By combining different tiers, you can achieve a balance between cache performance and size.
+A tiered cache is a multi-level cache in which each tier has its own characteristics and performance levels. By combining different tiers, you can achieve a balance between cache performance and size.
 
 ## Types of tiered caches
 
-OpenSearch 2.13 provides an implementation of _tiered spillover cache_. This implementation spills the evicted items from upper to lower tiers. The upper tier is smaller in size but offers better latency, like the on-heap tier. The lower tier is larger in size but is slower in terms of latency compared to the upper tier. A disk cache is an example of a lower tier. OpenSearch 2.13 offers on-heap and disk tiers. 
+OpenSearch 2.13 provides an implementation of a _tiered spillover cache_. This implementation spills the evicted items from upper to lower tiers. An upper tier, such as an on-heap tier, is smaller in size but offers better latency. A lower tier, such as a disk cache, is larger in size but is slower in terms of latency. OpenSearch 2.13 offers on-heap and disk tiers. 
 
 ## Enabling a tiered cache
 
@@ -30,7 +30,7 @@ For more information about ways to enable experimental features, see [Experiment
 
 ## Installing required plugins
 
-A tiered cache provides a way to plug in any disk or on-heap tier implementation. You can install the plugins you intend to use in the tiered cache. As of OpenSearch 2.13, the available cache plugin is the `cache-ehcache` plugin. This plugin provides a disk cache implementation to use within a tiered cache as a disk tier. 
+To use tiered caching, install a tiered cache plugin. As of OpenSearch 2.13, the only available cache plugin is the `cache-ehcache` plugin. This plugin provides a disk cache implementation to use within a tiered cache as a disk tier. For more information about installing non-bundled plugins, see [Additional plugins]({{site.url}}{{site.baseurl}}/install-and-configure/plugins/#additional-plugins).
 
 A tiered cache will fail to initialize if the `cache-ehcache` plugin is not installed or disk cache properties are not set.
 {: .warning}
@@ -41,42 +41,44 @@ In OpenSearch 2.13, a request cache can use a tiered cache. To begin, configure
 
 ### Cache store name
 
-Set the cache store name to `tiered_spillover` to use the OpenSearch-provided tiered spillover cache implementation:
+To use the OpenSearch-provided tiered spillover cache implementation, set the cache store name to `tiered_spillover`:
 
 ```yaml
-indices.request.cache.store.name: tiered_spillover: true
+indices.request.cache.store.name: tiered_spillover
 ```
 {% include copy.html %}
 
 ### Setting on-heap and disk store tiers
 
-The `opensearch_onheap` setting is the built-in on-heap cache available in OpenSearch. The `ehcache_disk` setting is the disk cache implementation from [Ehcache](https://www.ehcache.org/). This requires installing the `cache-ehcache` plugin:
+Set the on-heap and disk store tiers as follows:
 
 ```yaml
 indices.request.cache.tiered_spillover.onheap.store.name: opensearch_onheap
 indices.request.cache.tiered_spillover.disk.store.name: ehcache_disk
 ```
 {% include copy.html %}
 
-For more information about installing non-bundled plugins, see [Additional plugins]({{site.url}}{{site.baseurl}}/install-and-configure/plugins/#additional-plugins).
+The `opensearch_onheap` setting specifies to use the built-in on-heap cache available in OpenSearch. 
+
+The `ehcache_disk` setting specifies to use the disk cache implementation from [Ehcache](https://www.ehcache.org/). Using `ehcache_disk` requires installing the `cache-ehcache` plugin. 
 
 ### Configuring on-heap and disk stores
 
 The following table lists the cache store settings for the `opensearch_onheap` store.
 
-Setting | Default | Description
-:--- | :--- | :---
-`indices.request.cache.opensearch_onheap.size` | 1% of the heap | The size of the on-heap cache. Optional.
-`indices.request.cache.opensearch_onheap.expire` | `MAX_VALUE` (disabled) | Specify a time-to-live (TTL) for the cached results. Optional.
+Setting | Data type | Default | Description
+:--- | :--- | :--- | :---
+`indices.request.cache.opensearch_onheap.size` | Percentage (for example, `1%`) | 1% of the heap | The size of the on-heap cache. Optional.
+`indices.request.cache.opensearch_onheap.expire` | Integer | `MAX_VALUE` (disabled) | Specify a time-to-live (TTL) for the cached results. Optional.
 
 The following table lists the disk cache store settings for the `ehcache_disk` store.
 
-Setting | Default | Description
-:--- | :--- | :---
-`indices.request.cache.ehcache_disk.max_size_in_bytes` | `1073741824` (1 GB)  | Defines the size of the disk cache. Optional.
-`indices.request.cache.ehcache_disk.storage.path` | `""` | Defines the storage path for the disk cache. Required.
-`indices.request.cache.ehcache_disk.expire_after_access` | `MAX_VALUE` (disabled) | Specify a time-to-live (TTL) for the cached results. Optional.
-`indices.request.cache.ehcache_disk.alias` | `ehcacheDiskCache#INDICES_REQUEST_CACHE` (this is an example of request cache) | Specify an alias for the disk cache. Optional.
-`indices.request.cache.ehcache_disk.segments` | `16` | Defines the number of segments the disk cache is separated into. Used for concurrency. Optional.
-`indices.request.cache.ehcache_disk.concurrency` | `1` | Defines the number of distinct write queues created for the disk store, where a group of segments share a write queue. Optional.
+Setting | Data type | Default | Description
+:--- | :--- | :--- | :---
+`indices.request.cache.ehcache_disk.storage.path` | String | `""` | Defines the storage path for the disk cache. Required.
+`indices.request.cache.ehcache_disk.max_size_in_bytes` | Integer | `1073741824` (1 GB)  | Defines the size of the disk cache, in bytes. Optional.
+`indices.request.cache.ehcache_disk.expire_after_access` | Integer | `MAX_VALUE` (disabled) | Specify a time-to-live (TTL) for the cached results. Optional.
+`indices.request.cache.ehcache_disk.alias` | String | `ehcacheDiskCache#INDICES_REQUEST_CACHE` (this is an example of request cache) | Specify an alias for the disk cache. Optional.
+`indices.request.cache.ehcache_disk.segments` | Integer | `16` | Defines the number of segments the disk cache is separated into. Used for concurrency. Optional.
+`indices.request.cache.ehcache_disk.concurrency` | Integer | `1` | Defines the number of distinct write queues created for the disk store, where a group of segments share a write queue. Optional.