From a5817d7149bc9d85767aa6a2c8474a9099e5a88f Mon Sep 17 00:00:00 2001
From: rkargMsft <164392675+rkargMsft@users.noreply.github.com>
Date: Thu, 19 Mar 2026 07:55:23 -0700
Subject: [PATCH] Document RequestContext access in placement and placement
 filtering

Added example code for accessing RequestContext data during placement filtering.
---
 docs/orleans/grains/request-context.md | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/docs/orleans/grains/request-context.md b/docs/orleans/grains/request-context.md
index 66abf04f124b7..71e41873ecf14 100644
--- a/docs/orleans/grains/request-context.md
+++ b/docs/orleans/grains/request-context.md
@@ -114,3 +114,28 @@ Console.WriteLine(message);
 ```
 
 In this example, the client sets the trace ID to "example-id-set-by-client" before calling the `SayHello` method on the `HelloGrain`. The grain retrieves the trace ID from the request context and logs it.
+
+## Example placement access code
+
+The <xref:Orleans.Runtime.RequestContext> data can be accessed during Placement or Placement Filtering through the <xref:Orleans.Runtime.Placement.PlacementTarget> `RequestContextData`. The static <xref:Orleans.Runtime.RequestContext> is not populated at this time as there is not yet an activation of the grain.  The following placement filter code demonstrates how to get <xref:Orleans.Runtime.RequestContext> data while handling placement:
+
+```csharp
+internal sealed class ExamplePlacementFilterDirector(ILogger<ExamplePlacementFilterDirector> logger)
+    : IPlacementFilterDirector
+{
+    public IEnumerable<SiloAddress> Filter(
+        PlacementFilterStrategy filterStrategy,
+        PlacementTarget target,
+        IEnumerable<SiloAddress> silos)
+    {
+        if (target.RequestContextData.TryGetValue("somekey", out var somevalue) 
+            && somevalue is string somestring)
+        {
+            logger.LogInformation("Read {Value} for {Key} from the RequestContext", somestring, "somekey");
+            // somestring is available for the filtering logic
+        }
+        return silos;
+    }
+}
+```
+In this example, the "somekey" value is read from the <xref:Orleans.Runtime.Placement.PlacementTarget> `RequestContextData` during the placement filtering.