Fix RMI context propagation (#16979)

Co-authored-by: Lauri Tulmin <ltulmin@splunk.com>

Author: trask

CHANGELOG.md

@@ -1,5 +1,12 @@
 # Changelog
 
+## Version 2.26.1 (2026-03-23)
+
+### 🛠️ Bug fixes
+
+- Fix RMI context propagation
+  ([#16979](https://github.com/open-telemetry/opentelemetry-java-instrumentation/pull/16979))
+
 ## Version 2.26.0 (2026-03-13)
 
 ### ⚠️ Breaking changes to non-stable APIs

README.md

@@ -33,7 +33,7 @@ If you are looking for documentation on using those.
 ## Getting Started
 
 Download
-the [latest version](https://github.com/open-telemetry/opentelemetry-java-instrumentation/releases/download/v2.26.0/opentelemetry-javaagent.jar).
+the [latest version](https://github.com/open-telemetry/opentelemetry-java-instrumentation/releases/download/v2.26.1/opentelemetry-javaagent.jar).
 
 This package includes the instrumentation agent as well as
 instrumentations for all supported libraries and all available data exporters.

docs/apidiffs/current_vs_latest/opentelemetry-instrumentation-annotations.txt

@@ -1,2 +1,2 @@
-Comparing source compatibility of opentelemetry-instrumentation-annotations-2.26.0.jar against opentelemetry-instrumentation-annotations-2.25.0.jar
+Comparing source compatibility of opentelemetry-instrumentation-annotations-2.26.1.jar against opentelemetry-instrumentation-annotations-2.25.0.jar
 No changes.

docs/apidiffs/current_vs_latest/opentelemetry-instrumentation-api.txt

@@ -1,2 +1,2 @@
-Comparing source compatibility of opentelemetry-instrumentation-api-2.26.0.jar against opentelemetry-instrumentation-api-2.25.0.jar
+Comparing source compatibility of opentelemetry-instrumentation-api-2.26.1.jar against opentelemetry-instrumentation-api-2.25.0.jar
 No changes.

docs/apidiffs/current_vs_latest/opentelemetry-spring-boot-autoconfigure.txt

@@ -1,2 +1,2 @@
-Comparing source compatibility of opentelemetry-spring-boot-autoconfigure-2.26.0.jar against opentelemetry-spring-boot-autoconfigure-2.25.0.jar
+Comparing source compatibility of opentelemetry-spring-boot-autoconfigure-2.26.1.jar against opentelemetry-spring-boot-autoconfigure-2.25.0.jar
 No changes.

docs/apidiffs/current_vs_latest/opentelemetry-spring-boot-starter.txt

@@ -1,2 +1,2 @@
-Comparing source compatibility of opentelemetry-spring-boot-starter-2.26.0.jar against opentelemetry-spring-boot-starter-2.25.0.jar
+Comparing source compatibility of opentelemetry-spring-boot-starter-2.26.1.jar against opentelemetry-spring-boot-starter-2.25.0.jar
 No changes.

examples/distro/build.gradle

@@ -14,7 +14,7 @@ buildscript {
   dependencies {
     classpath "com.diffplug.spotless:spotless-plugin-gradle:8.3.0"
     classpath "com.gradleup.shadow:shadow-gradle-plugin:9.3.2"
-    classpath "io.opentelemetry.instrumentation:gradle-plugins:2.26.0-alpha"
+    classpath "io.opentelemetry.instrumentation:gradle-plugins:2.26.1-alpha"
   }
 }
 
@@ -30,8 +30,8 @@ subprojects {
       opentelemetrySdk           : "1.60.1",
 
       // these lines are managed by .github/scripts/update-version.sh
-      opentelemetryJavaagent     : "2.26.0",
-      opentelemetryJavaagentAlpha: "2.26.0-alpha",
+      opentelemetryJavaagent     : "2.26.1",
+      opentelemetryJavaagentAlpha: "2.26.1-alpha",
 
       autoservice                : "1.1.1"
     ]

examples/extension/build.gradle

@@ -13,8 +13,8 @@ plugins {
   id "com.gradleup.shadow" version "9.3.2"
   id "com.diffplug.spotless" version "8.3.0"
 
-  id "io.opentelemetry.instrumentation.muzzle-generation" version "2.26.0-alpha"
-  id "io.opentelemetry.instrumentation.muzzle-check" version "2.26.0-alpha"
+  id "io.opentelemetry.instrumentation.muzzle-generation" version "2.26.1-alpha"
+  id "io.opentelemetry.instrumentation.muzzle-check" version "2.26.1-alpha"
 }
 
 group 'io.opentelemetry.example'
@@ -26,8 +26,8 @@ ext {
     opentelemetrySdk           : "1.60.1",
 
     // these lines are managed by .github/scripts/update-version.sh
-    opentelemetryJavaagent     : "2.26.0",
-    opentelemetryJavaagentAlpha: "2.26.0-alpha"
+    opentelemetryJavaagent     : "2.26.1",
+    opentelemetryJavaagentAlpha: "2.26.1-alpha"
   ]
 
   deps = [

instrumentation/rmi/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/rmi/context/ContextPayload.java

@@ -17,11 +17,13 @@
 import java.util.HashMap;
 import java.util.Map;
 import java.util.logging.Logger;
+import javax.annotation.Nullable;
 
 /** ContextPayload wraps context information shared between client and server. */
 public class ContextPayload {
 
   private static final Logger logger = Logger.getLogger(ContextPayload.class.getName());
+  private static final int MAX_CONTEXT_ENTRIES = 1000;
 
   private final Map<String, String> context;
 
@@ -41,24 +43,40 @@ public static ContextPayload from(Context context) {
     return payload;
   }
 
-  @SuppressWarnings("BanSerializableRead") // fine
+  @Nullable
   public static ContextPayload read(ObjectInput oi) throws IOException {
-    try {
-      Object object = oi.readObject();
-      if (object instanceof Map) {
-        @SuppressWarnings("unchecked") // convert it back to the expected type
-        Map<String, String> map = (Map<String, String>) object;
-        return new ContextPayload(map);
-      }
-    } catch (ClassCastException | ClassNotFoundException ex) {
-      logger.log(FINE, "Error reading object", ex);
+    int size = oi.readInt();
+    if (size > MAX_CONTEXT_ENTRIES) {
+      logger.log(
+          FINE,
+          "RMI context propagation payload size {0} exceeds maximum allowed of {1}, skipping context propagation.",
+          new Object[] {size, MAX_CONTEXT_ENTRIES});
+      return null;
     }
-
-    return null;
+    Map<String, String> map = new HashMap<>();
+    for (int i = 0; i < size; i++) {
+      String key = oi.readUTF();
+      String value = oi.readUTF();
+      map.put(key, value);
+    }
+    return new ContextPayload(map);
   }
 
   public void write(ObjectOutput out) throws IOException {
-    out.writeObject(context);
+    int size = context.size();
+    if (size > MAX_CONTEXT_ENTRIES) {
+      logger.log(
+          FINE,
+          "RMI context propagation payload size {0} exceeds maximum allowed of {1}, skipping context propagation.",
+          new Object[] {size, MAX_CONTEXT_ENTRIES});
+      out.writeInt(0);
+      return;
+    }
+    out.writeInt(size);
+    for (Map.Entry<String, String> entry : context.entrySet()) {
+      out.writeUTF(entry.getKey());
+      out.writeUTF(entry.getValue());
+    }
   }
 
   public Context extract() {

instrumentation/rmi/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/rmi/context/ContextPropagator.java

@@ -32,7 +32,7 @@ public class ContextPropagator {
 
   // RMI object id used to identify agent instrumentation
   public static final ObjID CONTEXT_CALL_ID =
-      new ObjID("io.opentelemetry.javaagent.context-call".hashCode());
+      new ObjID("io.opentelemetry.javaagent.context-call-v2".hashCode());
 
   // Operation id used for checking context propagation is possible
   // RMI expects these operations to have negative identifier, as positive ones mean legacy