some tests

server/src/main/java/org/elasticsearch/rest/DeprecationRestHandler.java

@@ -38,6 +38,8 @@ public class DeprecationRestHandler extends FilterRestHandler implements RestHan
      * @param handler The rest handler to deprecate (it's possible that the handler is reused with a different name!)
      * @param method a method of a deprecated endpoint
      * @param path a path of a deprecated endpoint
+     * @param deprecationLevel The level of the deprecation warning, must be non-null
+     *                         and either {@link Level#WARN} or {@link DeprecationLogger#CRITICAL}
      * @param deprecationMessage The message to warn users with when they use the {@code handler}
      * @param deprecationLogger The deprecation logger
      * @param compatibleVersionWarning set to false so that a deprecation warning will be issued for the handled request,
@@ -60,7 +62,7 @@ public DeprecationRestHandler(
         this.deprecationLogger = Objects.requireNonNull(deprecationLogger);
         this.compatibleVersionWarning = compatibleVersionWarning;
         this.deprecationKey = DEPRECATED_ROUTE_KEY + "_" + method + "_" + path;
-        if (deprecationLevel != Level.WARN || deprecationLevel != DeprecationLogger.CRITICAL) {
+        if (deprecationLevel != Level.WARN && deprecationLevel != DeprecationLogger.CRITICAL) {
             throw new IllegalArgumentException(
                 "unexpected deprecation logger level: " + deprecationLevel + ", expected either 'CRITICAL' or 'WARN'"
             );
@@ -137,4 +139,9 @@ public static String requireValidHeader(String value) {
 
         return value;
     }
+
+    // test only
+    Level getDeprecationLevel() {
+        return deprecationLevel;
+    }
 }

server/src/main/java/org/elasticsearch/rest/RestController.java

@@ -237,7 +237,8 @@ protected void registerAsReplacedHandler(
             + "] instead.";
 
         registerHandler(method, path, version, handler);
-        Level deprecationLevel = version == RestApiVersion.current() ? Level.WARN : DeprecationLogger.CRITICAL;
+        //TODO: test this variant
+        Level deprecationLevel = replacedVersion == RestApiVersion.current() ? Level.WARN : DeprecationLogger.CRITICAL;
         registerAsDeprecatedHandler(replacedMethod, replacedPath, replacedVersion, handler, replacedMessage, deprecationLevel);
     }
 
@@ -282,8 +283,7 @@ public void registerHandler(final Route route, final RestHandler handler) {
                 handler,
                 replaced.getMethod(),
                 replaced.getPath(),
-                replaced.getRestApiVersion(),
-                replaced.getDeprecationLevel()
+                replaced.getRestApiVersion()
             );
         } else if (route.isDeprecated()) {
             registerAsDeprecatedHandler(

server/src/main/java/org/elasticsearch/rest/RestHandler.java

@@ -139,7 +139,6 @@ class Route {
         private final RestApiVersion restApiVersion;
         @Nullable
         private final String deprecationMessage;
-        @Nullable
         private final Level deprecationLevel;
         @Nullable
         private final Route replacedRoute;
@@ -149,7 +148,7 @@ private Route(
             String path,
             RestApiVersion restApiVersion,
             String deprecationMessage,
-            @Nullable Level deprecationLevel,
+            Level deprecationLevel,
             Route replacedRoute
         ) {
             this.method = Objects.requireNonNull(method);
@@ -174,7 +173,7 @@ private Route(
          * @param path   the path, e.g. "/"
          */
         public Route(Method method, String path) {
-            this(method, path, RestApiVersion.current(), null, null, null);
+            this(method, path, RestApiVersion.current(), null, Level.OFF, null);
         }
 
         public static class RouteBuilder {
@@ -279,7 +278,7 @@ public Route build() {
                     path,
                     restApiVersion,
                     deprecationMessage,
-                    deprecationLevel,
+                    deprecationLevel == null ? Level.OFF : deprecationLevel,
                     replacedRoute
                 );
 

server/src/test/java/org/elasticsearch/rest/DeprecationRestHandlerTests.java

@@ -73,7 +73,7 @@ public void testHandleRequestLogsThenForwards() throws Exception {
             RestChannel channel = mock(RestChannel.class);
             NodeClient client = mock(NodeClient.class);
 
-            final Level deprecationLevel = randomBoolean() ? null : randomFrom(Level.WARN, DeprecationLogger.CRITICAL);
+            final Level deprecationLevel = randomFrom(Level.WARN, DeprecationLogger.CRITICAL);
 
             DeprecationRestHandler deprecatedHandler = new DeprecationRestHandler(
                 handler,
@@ -159,17 +159,65 @@ public void testInvalidHeaderValueEmpty() {
     public void testSupportsBulkContentTrue() {
         when(handler.supportsBulkContent()).thenReturn(true);
         assertTrue(
-            new DeprecationRestHandler(handler, METHOD, PATH, null, deprecationMessage, deprecationLogger, false).supportsBulkContent()
+            new DeprecationRestHandler(handler, METHOD, PATH, Level.WARN, deprecationMessage, deprecationLogger, false)
+                .supportsBulkContent()
         );
     }
 
     public void testSupportsBulkContentFalse() {
         when(handler.supportsBulkContent()).thenReturn(false);
         assertFalse(
-            new DeprecationRestHandler(handler, METHOD, PATH, null, deprecationMessage, deprecationLogger, false).supportsBulkContent()
+            new DeprecationRestHandler(handler, METHOD, PATH, Level.WARN, deprecationMessage, deprecationLogger, false)
+                .supportsBulkContent()
         );
     }
 
+    public void testDeprecationLevel(){
+        DeprecationRestHandler handler = new DeprecationRestHandler(
+            this.handler,
+            METHOD,
+            PATH,
+            Level.WARN,
+            deprecationMessage,
+            deprecationLogger,
+            false
+        );
+        assertEquals(Level.WARN, handler.getDeprecationLevel());
+
+        handler = new DeprecationRestHandler(
+            this.handler,
+            METHOD,
+            PATH,
+            DeprecationLogger.CRITICAL,
+            deprecationMessage,
+            deprecationLogger,
+            false
+        );
+        assertEquals(DeprecationLogger.CRITICAL, handler.getDeprecationLevel());
+
+        IllegalArgumentException exception = expectThrows(IllegalArgumentException.class, () -> new DeprecationRestHandler(
+            this.handler,
+            METHOD,
+            PATH,
+            null,
+            deprecationMessage,
+            deprecationLogger,
+            false
+        ));
+        assertEquals(exception.getMessage(), "unexpected deprecation logger level: null, expected either 'CRITICAL' or 'WARN'");
+
+        exception = expectThrows(IllegalArgumentException.class, () -> new DeprecationRestHandler(
+            this.handler,
+            METHOD,
+            PATH,
+            Level.OFF,
+            deprecationMessage,
+            deprecationLogger,
+            false
+        ));
+        assertEquals(exception.getMessage(), "unexpected deprecation logger level: OFF, expected either 'CRITICAL' or 'WARN'");
+    }
+
     /**
      * {@code ASCIIHeaderGenerator} only uses characters expected to be valid in headers (simplified US-ASCII).
      */

server/src/test/java/org/elasticsearch/rest/RestControllerTests.java

@@ -9,6 +9,7 @@
 
 package org.elasticsearch.rest;
 
+import org.apache.logging.log4j.Level;
 import org.elasticsearch.ElasticsearchStatusException;
 import org.elasticsearch.client.internal.node.NodeClient;
 import org.elasticsearch.common.breaker.CircuitBreaker;
@@ -17,6 +18,7 @@
 import org.elasticsearch.common.component.AbstractLifecycleComponent;
 import org.elasticsearch.common.io.stream.BytesStream;
 import org.elasticsearch.common.io.stream.RecyclerBytesStreamOutput;
+import org.elasticsearch.common.logging.DeprecationLogger;
 import org.elasticsearch.common.settings.ClusterSettings;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.transport.BoundTransportAddress;
@@ -85,6 +87,7 @@
 import static org.mockito.ArgumentMatchers.anyMap;
 import static org.mockito.ArgumentMatchers.anyString;
 import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.clearInvocations;
 import static org.mockito.Mockito.doCallRealMethod;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.spy;
@@ -351,12 +354,12 @@ public void testRegisterAsDeprecatedHandler() {
         String deprecationMessage = randomAlphaOfLengthBetween(1, 10);
         RestApiVersion deprecatedInVersion = RestApiVersion.current();
 
-        Route route = Route.builder(method, path).deprecated(deprecationMessage, deprecatedInVersion).build();
+        Route route = Route.builder(method, path).deprecatedForRemoval(deprecationMessage, deprecatedInVersion).build();
 
         // don't want to test everything -- just that it actually wraps the handler
         doCallRealMethod().when(controller).registerHandler(route, handler);
         doCallRealMethod().when(controller)
-            .registerAsDeprecatedHandler(method, path, deprecatedInVersion, handler, deprecationMessage, null);
+            .registerAsDeprecatedHandler(method, path, deprecatedInVersion, handler, deprecationMessage, DeprecationLogger.CRITICAL);
 
         controller.registerHandler(route, handler);
 
@@ -383,17 +386,41 @@ public void testRegisterAsReplacedHandler() {
             + path
             + "] instead.";
 
-        final Route route = Route.builder(method, path).replaces(replacedMethod, replacedPath, previous).build();
-
-        // don't want to test everything -- just that it actually wraps the handlers
-        doCallRealMethod().when(controller).registerHandler(route, handler);
-        doCallRealMethod().when(controller)
-            .registerAsReplacedHandler(method, path, current, handler, replacedMethod, replacedPath, previous);
-
-        controller.registerHandler(route, handler);
-
-        verify(controller).registerHandler(method, path, current, handler);
-        verify(controller).registerAsDeprecatedHandler(replacedMethod, replacedPath, previous, handler, deprecationMessage);
+        List<RestApiVersion> replacedInVersions = List.of(current, previous);
+        for (RestApiVersion replacedInVersion : replacedInVersions) {
+            clearInvocations(controller);
+            Route route = Route.builder(method, path).replaces(replacedMethod, replacedPath, replacedInVersion).build();
+
+            // don't want to test everything -- just that it actually wraps the handler
+            doCallRealMethod().when(controller).registerHandler(route, handler);
+            doCallRealMethod().when(controller)
+                .registerAsReplacedHandler(method, path, current, handler, replacedMethod, replacedPath, replacedInVersion);
+
+            controller.registerHandler(route, handler);
+
+            verify(controller).registerHandler(method, path, current, handler);
+            if (replacedInVersion.equals(current)) {
+                // is replaced in current version, which results in a critical deprecation warning
+                verify(controller).registerAsDeprecatedHandler(
+                    replacedMethod,
+                    replacedPath,
+                    replacedInVersion,
+                    handler,
+                    deprecationMessage,
+                    Level.WARN
+                );
+            } else {
+                // is replaced in previous version, which results in a critical deprecation warning
+                verify(controller).registerAsDeprecatedHandler(
+                    replacedMethod,
+                    replacedPath,
+                    replacedInVersion,
+                    handler,
+                    deprecationMessage,
+                    DeprecationLogger.CRITICAL
+                );
+            }
+        }
     }
 
     public void testRegisterSecondMethodWithDifferentNamedWildcard() {