in_tail: add thread ring buffer configuration options (#2320)

Add thread.ring_buffer.capacity and thread.ring_buffer.window configuration
parameters to the Tail input plugin documentation. These options control the
ring buffer behavior when running in threaded mode.

Signed-off-by: jinyong.choi <[email protected]>

Author: jinyongchoi

pipeline/inputs/tail.md

@@ -45,6 +45,8 @@ The plugin supports the following configuration parameters:
 | `static_batch_size` | Set the maximum number of bytes to process per iteration for the monitored static files (files that already exist upon Fluent Bit start). | `50M` |
 | `tag` | Set a tag with `regexextract` fields that will be placed on lines read. For example, `kube.<namespace_name>.<pod_name>.<container_name>.<container_id>`. Tag expansion is supported: if the tag includes an asterisk (`*`), that asterisk will be replaced with the absolute path of the monitored file, with slashes replaced by dots. See [Workflow of Tail + Kubernetes Filter](../filters/kubernetes.md#workflow-of-tail--kubernetes-filter). | _none_ |
 | `tag_regex` | Set a regular expression to extract fields from the filename. For example: `(?<pod_name>[a-z0-9](?:[-a-z0-9]*[a-z0-9])?(?:\\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*)_(?<namespace_name>[^_]+)_(?<container_name>.+)-(?<container_id>[a-z0-9]{64})\.log$`. | _none_ |
+| `thread.ring_buffer.capacity` | Number of slots in the ring buffer for data entries when running in [threaded](../../administration/multithreading.md) mode. Each slot can hold one data entry. | `1024` |
+| `thread.ring_buffer.window` | Percentage threshold (1-100) of the ring buffer capacity at which a flush is triggered when running in [threaded](../../administration/multithreading.md) mode. | `5` |
 | `threaded` | Indicates whether to run this input in its own [thread](../../administration/multithreading.md#inputs). | `false` |
 | `truncate_long_lines` | When enabled, truncates lines that exceed the buffer capacity after input encoding conversion to UTF-8. Use this option when dealing with character encoding conversions that might expand the line length. | `false` |
 | `unicode.encoding` | Set the Unicode character encoding of the file data. This parameter requests two-byte aligned chunk and buffer sizes. If data isn't aligned for two bytes, Fluent Bit will use two-byte alignment automatically to avoid character breakages on consuming boundaries. Supported values: `UTF-16LE`, `UTF-16BE`, and `auto`. | _none_ |