Align rmi context propagation limits with tomcat (open-telemetry#17870)

Author: laurit

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

@@ -23,7 +23,11 @@
 public class ContextPayload {
 
   private static final Logger logger = Logger.getLogger(ContextPayload.class.getName());
-  private static final int MAX_CONTEXT_ENTRIES = 1000;
+  // using limits similar to Tomcat's maxHeaderCount and maxHttpHeaderSize
+  // https://tomcat.apache.org/tomcat-9.0-doc/config/http.html
+  private static final int MAX_CONTEXT_ENTRIES = 100;
+  // Tomcat limits in bytes we use character count
+  private static final int MAX_CONTEXT_SIZE = 8 * 1024;
 
   private final Map<String, String> context;
 
@@ -49,14 +53,23 @@ public static ContextPayload read(ObjectInput oi) throws IOException {
     if (size > MAX_CONTEXT_ENTRIES) {
       logger.log(
           FINE,
-          "RMI context propagation payload size {0} exceeds maximum allowed of {1}, skipping context propagation.",
+          "RMI context propagation entries count {0} exceeds maximum allowed of {1}, skipping context propagation.",
           new Object[] {size, MAX_CONTEXT_ENTRIES});
       return null;
     }
+    int contextSize = 0;
     Map<String, String> map = new HashMap<>();
     for (int i = 0; i < size; i++) {
       String key = oi.readUTF();
       String value = oi.readUTF();
+      contextSize += key.length() + value.length();
+      if (contextSize > MAX_CONTEXT_SIZE) {
+        logger.log(
+            FINE,
+            "RMI context propagation payload size exceeds maximum allowed of {0}, skipping context propagation.",
+            new Object[] {MAX_CONTEXT_SIZE});
+        return null;
+      }
       map.put(key, value);
     }
     return new ContextPayload(map);
@@ -67,7 +80,7 @@ public void write(ObjectOutput out) throws IOException {
     if (size > MAX_CONTEXT_ENTRIES) {
       logger.log(
           FINE,
-          "RMI context propagation payload size {0} exceeds maximum allowed of {1}, skipping context propagation.",
+          "RMI context propagation entries count {0} exceeds maximum allowed of {1}, skipping context propagation.",
           new Object[] {size, MAX_CONTEXT_ENTRIES});
       out.writeInt(0);
       return;