Add Gateway deployment arch

content/en/docs/collector/deployment/gateway.md → content/en/docs/collector/deployment/gateway/index.md

@@ -4,7 +4,8 @@ description:
   Why and how to send signals to a single OTLP end-point and from there to
   backends
 weight: 3
-cSpell:ignore: hostnames loadbalancer loadbalancing
+# prettier-ignore
+cSpell:ignore: filelogreceiver hostmetricsreceiver hostnames loadbalancer loadbalancing resourcedetection
 ---
 
 The gateway collector deployment pattern consists of applications (or other
@@ -198,6 +199,42 @@ The load-balancing exporter emits metrics including
 that you can use for health and performance monitoring of the OTLP endpoint
 collector.
 
+## Typical Gateway deployment architecture
+
+A typical Gateway architecture involves running both Collector in Gateway mode
+and Agent mode.
+
+The following diagram shows a typical deployment architecture for a gateway
+deployment. Here
+
+- We use Agent Collectors (running on each host, similar to Kubernetes
+  daemonsets) to collect telemetry from services running on the host and host
+  telemetry, such as host metrics and scrap logs.
+- We use Gateway Collectors to process OTLP data, such as filtering, sampling,
+  and exporting to backends etc.
+
+![gateway](otel-gateway-arch.svg)
+
+There are a few limitations in running the OpenTelemetry Collector in gateway
+mode.
+
+- There are few receivers in OpenTelemetry Collector that need to be unique per
+  host instance. Running multiple instances of these receivers will result in
+  duplicate data. It is recommended not to use them in the Gateway Collector but
+  only for the collector running in Agent mode. Examples include, but are not
+  limited to:
+
+  - [`hostmetricsreceiver`](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/receiver/hostmetricsreceiver),
+    may result in duplicate host metrics.
+  - [`filelogreceiver`](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/receiver/filelogreceiver),
+    may result in duplicate logs.
+
+- Using a
+  [`resourcedetection`](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/processor/resourcedetectionprocessor)
+  processor in gateway mode is not recommended. This processor is used to detect
+  the resources of the host where the Collector is running. Use
+  `resourcedetection` processor in the pipeline of Agent collector deployment.
+
 ## Tradeoffs
 
 Pros: