adding example to getMetadata

_data-prepper/pipelines/get-metadata.md

@@ -14,29 +14,86 @@ If the key contains a `/`, then the function looks up the metadata recursively.
 
 The value returned can be of any type. For example, if the metadata contains `{"key1": "value2", "key2": 10}`, then the function `getMetadata("key1")` returns `value2`. The function `getMetadata("key2")` returns `10`.
 
-#### Example 
+## Example 
+
+The following pipeline writes request derived values into event metadata, then uses `getMetadata()` in the OpenSearch sink to build tenant scoped daily index names and document IDs:
+
+```yaml
+metadata-pass-demo:
+  source:
+    http:
+      ssl: false
+
+  processor:
+    - add_entries:
+        entries:
+          # write to metadata
+          - metadata_key: tenant        
+            value_expression: /tenant
+          - metadata_key: ingest_marker
+            value: batch-001
+    - add_entries:
+        entries:
+          - key: tenant_from_meta
+            value_expression: getMetadata("tenant")
+
+  sink:
+    - opensearch:
+        hosts: ["https://opensearch:9200"]
+        insecure: true
+        username: admin
+        password: admin_password
+        index_type: custom
+        # Use metadata inside sink format strings
+        index: demo-%{yyyy.MM.dd}-${getMetadata("tenant")}
+        document_id: ${/id}-${getMetadata("tenant")}
+```
+{% include copy.html %}
+
+You can test the pipeline using the following command:
+
+```bash
+curl -sS -X POST "http://localhost:2021/log/ingest" \
+  -H "Content-Type: application/json" \
+  -d '[{"id":"1","tenant":"eu","message":"hello"}, {"id":"2","tenant":"us","message":"hi"}]'
+```
+{% include copy.html %}
+
+The documents stored in OpenSearch contain the following information:
 
 ```json
 {
-  "event": {
-    "metadata": {
-      "key1": "value2",
-      "key2": 10
-    },
-    "data": {
-      // ...
-    }
-  },
-  "output": [
-    {
-      "key": "key1",
-      "value": "value2"
+  ...
+  "hits": {
+    "total": {
+      "value": 2,
+      "relation": "eq"
     },
-    {
-      "key": "key2",
-      "value": 10
-    }
-  ]
+    "max_score": 1,
+    "hits": [
+      {
+        "_index": "demo-2025.10.22-eu",
+        "_id": "1-eu",
+        "_score": 1,
+        "_source": {
+          "id": "1",
+          "tenant": "eu",
+          "message": "hello",
+          "tenant_from_meta": "eu"
+        }
+      },
+      {
+        "_index": "demo-2025.10.22-us",
+        "_id": "2-us",
+        "_score": 1,
+        "_source": {
+          "id": "2",
+          "tenant": "us",
+          "message": "hi",
+          "tenant_from_meta": "us"
+        }
+      }
+    ]
+  }
 }
 ```
-{% include copy.html %}