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Author: rjernst

server/src/main/java/org/elasticsearch/ElasticsearchException.java

@@ -129,9 +129,7 @@ public class ElasticsearchException extends RuntimeException implements ToXConte
     @SuppressWarnings("this-escape")
     public ElasticsearchException(Throwable cause) {
         super(cause);
-        if (isTimeout()) {
-            headers.put(TIMED_OUT_HEADER, List.of("true"));
-        }
+        maybePutTimeoutHeader();
     }
 
     /**
@@ -146,9 +144,7 @@ public ElasticsearchException(Throwable cause) {
     @SuppressWarnings("this-escape")
     public ElasticsearchException(String msg, Object... args) {
         super(LoggerMessageFormat.format(msg, args));
-        if (isTimeout()) {
-            headers.put(TIMED_OUT_HEADER, List.of("true"));
-        }
+        maybePutTimeoutHeader();
     }
 
     /**
@@ -165,9 +161,7 @@ public ElasticsearchException(String msg, Object... args) {
     @SuppressWarnings("this-escape")
     public ElasticsearchException(String msg, Throwable cause, Object... args) {
         super(LoggerMessageFormat.format(msg, args), cause);
-        if (isTimeout()) {
-            headers.put(TIMED_OUT_HEADER, List.of("true"));
-        }
+        maybePutTimeoutHeader();
     }
 
     @SuppressWarnings("this-escape")
@@ -178,6 +172,13 @@ public ElasticsearchException(StreamInput in) throws IOException {
         metadata.putAll(in.readMapOfLists(StreamInput::readString));
     }
 
+    private void maybePutTimeoutHeader() {
+        if (isTimeout()) {
+            // see https://www.rfc-editor.org/rfc/rfc8941.html#section-4.1.9 for booleans in structured headers
+            headers.put(TIMED_OUT_HEADER, List.of("?1"));
+        }
+    }
+
     /**
      * Adds a new piece of metadata with the given key.
      * If the provided key is already present, the corresponding metadata will be replaced

server/src/test/java/org/elasticsearch/ElasticsearchExceptionTests.java

@@ -1578,7 +1578,7 @@ public void testTimeout() throws IOException {
               "reason": "some timeout",
               "timed_out": true,
               "header": {
-                "X-Timed-Out": "true"
+                "X-Timed-Out": "?1"
               }
             }""";
         assertEquals(XContentHelper.stripWhitespace(expected), Strings.toString(builder));