diff --git a/plugins/output/http.md b/plugins/output/http.md
index d647955e..296c0eb1 100644
--- a/plugins/output/http.md
+++ b/plugins/output/http.md
@@ -86,12 +86,22 @@ The proxy for HTTP request
Content-Type for HTTP request. `out_http` automatically set `Content-Type` for built-in formatters when this parameter is not specified. Here is a table:
-* `json`: `application/x-ndjson`
+* `json(json_array: false)`: `application/x-ndjson`
+* `json(json_array: true)`: `application/json`
* `csv`: `text/csv`
* `tsv`, `ltsv`: `text/tab-separated-values`
* `msgpack`: `application/x-msgpack`
* `out_file`, `single_value`, `stdout`, `hash`: `text/plain`
+### json_array
+
+| type | default | version |
+|:-------|:--------|:--------|
+| bool | false | 1.10.4 |
+
+Using array format of JSON. This parameter is used and valid only for json format.
+When `json_array` as true, Content-Type should be `application/json` and be able to use JSON data for the HTTP request body.
+
### <format> directive
The format of the payload. The default `@type` is `json`. Here is `single_value` example:
@@ -282,6 +292,79 @@ log line4\n
...
```
+## Troubleshooting
+
+### 400 Bad request between out\_http and in\_http
+
+When getting the following error:
+
+```
+#0 got unrecoverable error in primary and no secondary error_class=Fluent::UnrecoverableError error="400 Bad Request 400 Bad Request\n'json' or 'msgpack' parameter is required\n"
+#0 bad chunk is moved to /tmp/fluent/backup/worker0/object_3ff8a73edae8/5a71a08ca19b1b343c8dce1b74c9a963.log
+```
+
+Users should be specify `json` format with `json_array` as true for out\_http configuration:
+
+```
+
+ @type http
+ endpoint http://some.your.http.endpoint:9811/your-awesome-path
+
+ @type json
+
+ json_array true
+
+ flush_interval 2s
+
+
+```
+
+And receiver in\_http configuration should be:
+
+```
+
+ @type http
+ port 9811
+ bind 0.0.0.0
+
+ @type json
+
+
+```
+
+Or specify msgpack format:
+
+```
+
+ @type http
+ endpoint http://some.your.http.endpoint:9882/your-awesome-path
+
+ @type msgpack
+
+
+ flush_interval 2s
+
+
+```
+
+And receiver in\_http configuration should be:
+
+```
+
+ @type http
+ port 9882
+ bind 0.0.0.0
+
+ @type msgpack
+
+
+ @type json
+
+
+```
+
+But, we recommend to use in/out [`forward`](forward.md) plugin to communicate with two Fluentds due to at-most-once and at-least-once semantics for rigidty.
+
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