address pr comments

x-pack/filebeat/docs/inputs/input-http-endpoint.asciidoc

@@ -379,10 +379,12 @@ observe the activity of the input.
 | `api_errors_total`        | Number of API errors.
 | `batches_received_total`  | Number of event arrays received.
 | `batches_published_total` | Number of event arrays published.
+| `batches_acked_total`     | Number of event arrays ACKed.
 | `events_published_total`  | Number of events published.
 | `size`                    | Histogram of request content lengths.
 | `batch_size`              | Histogram of the received event array length.
 | `batch_processing_time`   | Histogram of the elapsed successful batch processing times in nanoseconds (time of receipt to time of ACK for non-empty batches).
+| `batch_ack_time`          | Histogram of the elapsed successful batch ACKing times in nanoseconds (time of handler start to time of ACK for non-empty batches).
 |=======
 
 [id="{beatname_lc}-input-{type}-common-options"]

x-pack/filebeat/input/http_endpoint/ack.go

@@ -47,8 +47,8 @@ func newBatchACKTracker(fn func()) *batchACKTracker {
 }
 
 // Ready signals that the batch has been fully consumed. Only
-// after the batch is marked as "ready" can the lumberjack batch
-// be ACKed. This prevents the batch from being ACKed prematurely.
+// after the batch is marked as "ready" can the batch be ACKed.
+// This prevents the batch from being ACKed prematurely.
 func (t *batchACKTracker) Ready() {
 	t.ACK()
 }