DOCAPI-6213: Docs for send_progress_in_http_headers setting.

docs/en/interfaces/http.md

@@ -205,7 +205,13 @@ For information about other parameters, see the section "SET".
 
 Similarly, you can use ClickHouse sessions in the HTTP protocol. To do this, you need to add the `session_id` GET parameter to the request. You can use any string as the session ID. By default, the session is terminated after 60 seconds of inactivity. To change this timeout, modify the `default_session_timeout` setting in the server configuration, or add the `session_timeout` GET parameter to the request. To check the session status, use the `session_check=1` parameter. Only one query at a time can be executed within a single session.
 
-You have the option to receive information about the progress of query execution in X-ClickHouse-Progress headers. To do this, enable the setting send_progress_in_http_headers.
+You have the option to receive information about the progress of query execution in `X-ClickHouse-Progress` headers. To do this, enable the setting [send_progress_in_http_headers](../operations/settings/settings.md#settings-send_progress_in_http_headers). Example of the header:
+
+```
+X-ClickHouse-Progress: {"read_rows":"393216","read_bytes":"28368934","total_rows":"8880128"}
+```
+
+File [Progress.h](https://github.com/yandex/ClickHouse/blob/master/dbms/src/IO/Progress.h) contains structures `struct ProgressValues` and `struct Progress` which define fields that you see in the HTTP header.
 
 Running requests don't stop automatically if the HTTP connection is lost. Parsing and data formatting are performed on the server side, and using the network might be ineffective.
 The optional 'query_id' parameter can be passed as the query ID (any string). For more information, see the section "Settings, replace_running_query".

docs/en/operations/settings/settings.md

@@ -114,6 +114,19 @@ Possible values:
 
 Default value: 0.
 
+## send_progress_in_http_headers {#settings-send_progress_in_http_headers}
+
+Enables or disables sending of the `X-ClickHouse-Progress` header in an answer from `clickhouse-server`.
+
+For more information, read the [HTTP interface description](../../interfaces/http.md).
+
+Possible values:
+
+- 0 — Disabled.
+- 1 — Enabled.
+
+Default value: 0.
+
 ## input_format_allow_errors_num
 
 Sets the maximum number of acceptable errors when reading from text formats (CSV, TSV, etc.).