in_tail: Add a description and note for Unicode.Encoding parameter (#1471)

* in_tail: Add a description and note for Unicode.Encoding parameter

Signed-off-by: Hiroshi Hatake <[email protected]>

* Update pipeline/inputs/tail.md

Co-authored-by: Alexa Kreizinger <[email protected]>
Signed-off-by: Hiroshi Hatake <[email protected]>

---------

Signed-off-by: Hiroshi Hatake <[email protected]>
Co-authored-by: Alexa Kreizinger <[email protected]>

Author: cosmo0920

pipeline/inputs/tail.md

@@ -37,6 +37,7 @@ 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`     |
 | `file_cache_advise`   | Set the `posix_fadvise` in `POSIX_FADV_DONTNEED` mode. This reduces the usage of the kernel file cache. This option is ignored if not running on Linux.                                                                                                                                                                                                                                                                                                            | `on`      |
 | `threaded`            | Indicates whether to run this input in its own [thread](../../administration/multithreading.md#inputs).                                                                                                                                                                                                                                                                                                                                                            | `false`   |
+| `Unicode.Encoding`    | Set the Unicode character encoding of the file data. This parameter requests two-byte aligned chunk and buffer sizes. If data is not 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`    |
 
 ## Buffers and memory management
 
@@ -77,6 +78,12 @@ If no database file is present, positioning behavior depends on the value of `re
 
 The database file essentially stores `inode=offset` so it should be unique per instance of the plugin, for example if you have two tail inputs then use two separate `db` files for each. That way each tail input can independently track its own state.
 
+{% hint style="info" %}
+The `Unicode.Encoding` parameter is dependent on the simdutf library, which is itself dependent on C++ version 11 or later. In environments that use earlier versions of C++, the `Unicode.Encoding` parameter will fail.
+
+Additionally, the `auto` setting for `Unicode.Encoding` isn't supported in all cases, and can make mistakes when it tries to guess the correct encoding. For best results, use either the `UTF-16LE` or `UTF-16BE` setting if you know the encoding type of the target file.
+{% endhint %}
+
 ## Monitor a large number of files
 
 To monitor a large number of files, you can increase the `inotify` settings in your Linux environment by modifying the following `sysctl` parameters: