[Backport 2.5] Add Trace peer forwarder doc.

_data-prepper/pipelines/configuration/processors/trace-peer-forwarder.md

@@ -0,0 +1,52 @@
+---
+layout: default
+title: trace peer forwarder
+parent: Processors
+grand_parent: Pipelines
+nav_order: 45
+---
+
+# trace peer forwarder
+
+The `trace peer forwarder` processor is used with [peer forwarder]({{site.url}}{{site.baseurl}}/data-prepper/managing-data-prepper/peer-forwarder/) to reduce by half the number of events forwarded in a [Trace Analytics]({{site.url}}{{site.baseurl}}/data-prepper/common-use-cases/trace-analytics/) pipeline. In Trace Analytics, each event is typically duplicated when it is sent from `otel-trace-pipeline` to `raw-pipeline` and `service-map-pipeline`. When pipelines forward events, this causes the core peer forwarder to send multiple HTTP requests for the same event. You can use `trace peer forwarder` to forward an event once through the `otel-trace-pipeline` instead of `raw-pipeline` and `service-map-pipeline`, which prevents unnecessary HTTP requests.
+
+You should use `trace peer forwarder` for Trace Analytics pipelines when you have multiple nodes.
+
+## Usage
+
+To get started with `trace peer forwarder`, first configure [peer forwarder]({{site.url}}{{site.baseurl}}/data-prepper/managing-data-prepper/peer-forwarder/). Then create a `pipeline.yaml` file and specify `trace peer forwarder` as the processor. You can configure `peer forwarder` in your `data-prepper-config.yaml` file. For more detailed information, see [Configuring Data Prepper]({{site.url}}{{site.baseurl}}/data-prepper/getting-started/#2-configuring-data-prepper).
+
+See the following example `pipeline.yaml` file: 
+
+```yaml
+otel-trace-pipeline:
+  delay: "100"
+  source:
+    otel_trace_source:
+  processor:
+    - trace_peer_forwarder:
+  sink:
+    - pipeline:
+        name: "raw-pipeline"
+    - pipeline:
+        name: "service-map-pipeline"
+raw-pipeline:
+  source:
+    pipeline:
+      name: "entry-pipeline"
+  processor:
+    - otel_trace_raw:
+  sink:
+    - opensearch:
+service-map-pipeline:
+  delay: "100"
+  source:
+    pipeline:
+      name: "entry-pipeline"
+  processor:
+    - service_map_stateful:
+  sink:
+    - opensearch:
+```
+
+In the preceding `pipeline.yaml` file, events are forwarded in the `otel-trace-pipeline` to the target peer, and no forwarding is performed in `raw-pipeline` or `service-map-pipeline`. This process helps improve network performance by forwarding events (as HTTP requests) once instead of twice.