Use MVEL for rule evaluation

gateway-ha/pom.xml

@@ -270,6 +270,12 @@
             <version>${dep.jeasy.version}</version>
         </dependency>
 
+        <dependency>
+            <groupId>org.mvel</groupId>
+            <artifactId>mvel2</artifactId>
+            <version>2.5.2.Final</version>
+        </dependency>
+
         <dependency>
             <groupId>org.weakref</groupId>
             <artifactId>jmxutils</artifactId>
@@ -290,13 +296,6 @@
             <scope>runtime</scope>
         </dependency>
 
-        <dependency>
-            <groupId>org.mvel</groupId>
-            <artifactId>mvel2</artifactId>
-            <version>2.5.2.Final</version>
-            <scope>runtime</scope>
-        </dependency>
-
         <dependency>
             <groupId>org.postgresql</groupId>
             <artifactId>postgresql</artifactId>
@@ -513,6 +512,15 @@
                     </execution>
                 </executions>
             </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>22</source>
+                    <target>22</target>
+                    <compilerArgs>--enable-preview</compilerArgs>
+                </configuration>
+            </plugin>
         </plugins>
     </build>
 </project>

gateway-ha/src/main/java/io/trino/gateway/ha/router/MVELRoutingGroupSelector.java

@@ -0,0 +1,55 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.trino.gateway.ha.router;
+
+import com.google.common.collect.ImmutableMap;
+import jakarta.servlet.http.HttpServletRequest;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import static org.mvel2.MVEL.executeExpression;
+import static java.util.Collections.sort;
+
+public class MVELRoutingGroupSelector
+        implements RoutingGroupSelector
+{
+    final List<MVELRule> rules;
+
+    public MVELRoutingGroupSelector(List<MVELRule> rules)
+    {
+        this.rules = new ArrayList<>(rules);
+        sort(this.rules);
+    }
+
+    // TODO: add CRUD operations for the rules
+
+    @Override
+    public String findRoutingGroup(HttpServletRequest request)
+    {
+        Map<String, String> result = new HashMap<>();
+        Map<String, Object> variables = ImmutableMap.of("result", result, "request", request);
+        rules.forEach(rule -> evaluateMVELRule(rule, variables));
+        return result.getOrDefault("routingGroup", "adhoc");
+    }
+
+    private void evaluateMVELRule(MVELRule rule, Map<String, Object> variables)
+    {
+        if ((boolean) executeExpression(rule.condition(), variables)) {
+            executeExpression(rule.action(), variables);
+        }
+    }
+}

gateway-ha/src/main/java/io/trino/gateway/ha/router/MVELRule.java

@@ -0,0 +1,51 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.trino.gateway.ha.router;
+
+import java.io.Serializable;
+import org.mvel2.compiler.ExecutableStatement;
+
+import static java.util.Objects.requireNonNull;
+import static java.util.Objects.requireNonNullElse;
+import static org.mvel2.MVEL.compileExpression;
+
+
+public record MVELRule(String name, String description, Serializable condition, Serializable action, Integer priority)
+    implements Comparable<MVELRule>
+{
+    // String is Serializable - how can we ensure the condition and action are compiled?
+    public MVELRule(String name, String description, Serializable condition, Serializable action, Integer priority)
+    {
+        if (condition instanceof String stringCondition) {
+            condition = compileExpression(stringCondition);
+        }
+        if (action instanceof String stringAction) {
+            action = compileExpression(stringAction);
+        }
+        this.name = requireNonNull(name, "name is null");
+        this.description = requireNonNullElse(description, "");
+        this.condition = requireNonNull(condition, "condition is null");
+        this.action = requireNonNull(action, "action is null");
+        this.priority = requireNonNull(priority, "priority is null");
+    }
+
+    @Override
+    public int compareTo(MVELRule o)
+    {
+        if (o == null) {
+            return 1;
+        }
+        return priority.compareTo(o.priority);
+    }
+}

gateway-ha/src/test/java/io/trino/gateway/ha/TestMVELRoutingGroupSelector.java

@@ -0,0 +1,41 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.trino.gateway.ha;
+
+import com.google.common.collect.ImmutableList;
+import io.trino.gateway.ha.router.MVELRoutingGroupSelector;
+import io.trino.gateway.ha.router.MVELRule;
+import jakarta.servlet.http.HttpServletRequest;
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.mock;
+
+public class TestMVELRoutingGroupSelector
+{
+
+    @Test
+    void testMVELRoutingGroupSelector()
+    {
+        String condition = "request != null";
+        String action = "result.put(\"routingGroup\", \"custom\")";
+        List<MVELRule> rules = ImmutableList.of(new MVELRule("test", "test rule", condition, action, 0));
+        MVELRoutingGroupSelector mvelRoutingGroupSelector = new MVELRoutingGroupSelector(rules);
+
+        HttpServletRequest mockRequest = mock(HttpServletRequest.class);
+        assertThat(mvelRoutingGroupSelector.findRoutingGroup(mockRequest)).isEqualTo("custom");
+    }
+}