Zipkin: add ability to upload trace json (#37483)

* Zipkin: upload json

* Change back mock json

docs/sources/datasources/zipkin.md

@@ -32,7 +32,7 @@ This is a configuration for the [trace to logs feature]({{< relref "../explore/t
 
 - **Data source -** Target data source.
 - **Tags -** The tags that will be used in the Loki query. Default is `'cluster', 'hostname', 'namespace', 'pod'`.
-- **Span start time shift -** Shift in the start time for the Loki query based on the span start time. In order to extend to the past, you need to use a negative value.  Time units can be used here, for example, 5s, 1m, 3h. The default is 0.
+- **Span start time shift -** Shift in the start time for the Loki query based on the span start time. In order to extend to the past, you need to use a negative value. Use time interval units like 5s, 1m, 3h. The default is 0.
 - **Span end time shift -** Shift in the end time for the Loki query based on the span end time. Time units can be used here, for example, 5s, 1m, 3h. The default is 0.
 
 ![Trace to logs settings](/static/img/docs/explore/trace-to-logs-settings-8.png 'Screenshot of the trace to logs settings')
@@ -57,6 +57,36 @@ Use the trace selector to pick particular trace from all traces logged in the ti
 
 Zipkin annotations are shown in the trace view as logs with annotation value shown under annotation key.
 
+## Upload JSON trace file
+
+You can upload a JSON file that contains a single trace to visualize it.
+
+{{< figure src="/static/img/docs/explore/zipkin-upload-json.png" class="docs-image--no-shadow" caption="Screenshot of the Zipkin data source in explore with upload selected" >}}
+
+Here is an example JSON:
+
+```json
+[
+  {
+    "traceId": "efe9cb8857f68c8f",
+    "parentId": "efe9cb8857f68c8f",
+    "id": "8608dc6ce5cafe8e",
+    "kind": "SERVER",
+    "name": "get /api",
+    "timestamp": 1627975249601797,
+    "duration": 23457,
+    "localEndpoint": { "serviceName": "backend", "ipv4": "127.0.0.1", "port": 9000 },
+    "tags": {
+      "http.method": "GET",
+      "http.path": "/api",
+      "jaxrs.resource.class": "Resource",
+      "jaxrs.resource.method": "printDate"
+    },
+    "shared": true
+  }
+]
+```
+
 ## Linking Trace ID from logs
 
 You can link to Zipkin trace from logs in Loki by configuring a derived field with internal link. See [Loki documentation]({{< relref "loki#derived-fields" >}}) for details.