Improve error message for search.check_ccs_compatibility=true mode flag

modules/lang-mustache/src/internalClusterTest/java/org/elasticsearch/script/mustache/MultiSearchTemplateIT.java

@@ -18,6 +18,7 @@
 import org.elasticsearch.script.ScriptType;
 import org.elasticsearch.script.mustache.MultiSearchTemplateResponse.Item;
 import org.elasticsearch.search.DummyQueryParserPlugin;
+import org.elasticsearch.search.FailBeforeCurrentVersionQueryBuilder;
 import org.elasticsearch.search.SearchService;
 import org.elasticsearch.test.ESIntegTestCase;
 import org.elasticsearch.xcontent.json.JsonXContent;
@@ -200,9 +201,14 @@ public void testCCSCheckCompatibility() throws Exception {
         Exception ex = response.getFailure();
         assertThat(ex.getMessage(), containsString("[class org.elasticsearch.action.search.SearchRequest] is not compatible with version"));
         assertThat(ex.getMessage(), containsString("'search.check_ccs_compatibility' setting is enabled."));
-        assertEquals(
-            "This query isn't serializable with transport versions before " + TransportVersion.current(),
-            ex.getCause().getMessage()
+
+        String expectedCause = Strings.format(
+            "[fail_before_current_version] was released first in version %s, failed compatibility "
+                + "check trying to send it to node with version %s",
+            FailBeforeCurrentVersionQueryBuilder.FUTURE_VERSION,
+            TransportVersion.MINIMUM_CCS_VERSION
         );
+        String actualCause = ex.getCause().getMessage();
+        assertEquals(expectedCause, actualCause);
     }
 }

modules/lang-mustache/src/internalClusterTest/java/org/elasticsearch/script/mustache/SearchTemplateIT.java

@@ -8,7 +8,6 @@
 package org.elasticsearch.script.mustache;
 
 import org.elasticsearch.ResourceNotFoundException;
-import org.elasticsearch.TransportVersion;
 import org.elasticsearch.action.admin.cluster.storedscripts.GetStoredScriptResponse;
 import org.elasticsearch.action.bulk.BulkRequestBuilder;
 import org.elasticsearch.action.search.SearchRequest;
@@ -365,14 +364,22 @@ public void testCCSCheckCompatibility() throws Exception {
             ExecutionException.class,
             () -> client().execute(SearchTemplateAction.INSTANCE, request).get()
         );
+
+        Throwable primary = ex.getCause();
+        assertNotNull(primary);
+
+        Throwable underlying = primary.getCause();
+        assertNotNull(underlying);
+
         assertThat(
-            ex.getCause().getMessage(),
+            primary.getMessage(),
             containsString("[class org.elasticsearch.action.search.SearchRequest] is not compatible with version")
         );
-        assertThat(ex.getCause().getMessage(), containsString("'search.check_ccs_compatibility' setting is enabled."));
-        assertEquals(
-            "This query isn't serializable with transport versions before " + TransportVersion.current(),
-            ex.getCause().getCause().getMessage()
-        );
+        assertThat(primary.getMessage(), containsString("'search.check_ccs_compatibility' setting is enabled."));
+
+        String expectedCause = "[fail_before_current_version] was released first in version XXXXXXX, failed compatibility check trying to"
+            + " send it to node with version XXXXXXX";
+        String actualCause = underlying.getMessage().replaceAll("\\d{7,}", "XXXXXXX");
+        assertEquals(expectedCause, actualCause);
     }
 }

test/framework/src/main/java/org/elasticsearch/search/FailBeforeCurrentVersionQueryBuilder.java

@@ -10,7 +10,6 @@
 
 import org.elasticsearch.TransportVersion;
 import org.elasticsearch.common.io.stream.StreamInput;
-import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.index.query.QueryBuilder;
 import org.elasticsearch.index.query.QueryRewriteContext;
 import org.elasticsearch.xcontent.XContentParser;
@@ -23,22 +22,14 @@
 public class FailBeforeCurrentVersionQueryBuilder extends DummyQueryBuilder {
 
     public static final String NAME = "fail_before_current_version";
+    public static final int FUTURE_VERSION = TransportVersion.current().id() + 11_111;
 
     public FailBeforeCurrentVersionQueryBuilder(StreamInput in) throws IOException {
         super(in);
     }
 
     public FailBeforeCurrentVersionQueryBuilder() {}
 
-    @Override
-    protected void doWriteTo(StreamOutput out) {
-        if (out.getTransportVersion().before(TransportVersion.current())) {
-            throw new IllegalArgumentException(
-                "This query isn't serializable with transport versions before " + TransportVersion.current()
-            );
-        }
-    }
-
     public static DummyQueryBuilder fromXContent(XContentParser parser) throws IOException {
         DummyQueryBuilder.fromXContent(parser);
         return new FailBeforeCurrentVersionQueryBuilder();
@@ -53,4 +44,11 @@ public String getWriteableName() {
     protected QueryBuilder doRewrite(QueryRewriteContext queryRewriteContext) throws IOException {
         return this;
     }
+
+    @Override
+    public TransportVersion getMinimalSupportedVersion() {
+        // this is what causes the failure - it always reports a version in the future, so it is never compatible with
+        // current or minimum CCS TransportVersion
+        return new TransportVersion(FUTURE_VERSION);
+    }
 }