add docs

doc/api/geo_nodes.md

@@ -139,3 +139,36 @@ Example response:
   "last_successful_status_check_timestamp": 1510125268
 }
 ```
+
+## Retrieve project sync failures ocurred on a specific node (only available for the current node)
+
+
+```
+GET /geo_nodes/:id/failures
+```
+
+| Attribute | Type | Required | Description |
+| --------- | ---- | -------- | ----------- |
+| `type` | string | no | Type of failure (repository/wiki) |
+
+This function takes pagination parameters `page` and `per_page` to limit the list of failures.
+
+```bash
+curl --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/geo_nodes/2/failures
+```
+
+Example response:
+
+```json
+{
+    "project_id": 3,
+    "last_repository_synced_at": "2017-10-31 14:25:55 UTC",
+    "last_repository_successful_sync_at": "2017-10-31 14:26:04 UTC",
+    "last_wiki_synced_at": "2017-10-31 14:26:04 UTC",
+    "last_wiki_successful_sync_at": "2017-10-31 14:26:11 UTC",
+    "repository_retry_count": null,
+    "wiki_retry_count": 1,
+    "last_repository_sync_failure": null,
+    "last_wiki_sync_failure": "Error syncing Wiki repository"
+}
+```