| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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 org.apache.cassandra.db.guardrails; |
| |
| import java.util.function.Function; |
| import java.util.function.Predicate; |
| import javax.annotation.Nullable; |
| |
| import org.apache.cassandra.service.ClientState; |
| |
| /** |
| * A guardrail based on two predicates. |
| * |
| * <p>A {@link Predicates} guardrail defines (up to) 2 predicates, one at which a warning is issued, and another one |
| * at which a failure is triggered. If failure is triggered, warning is skipped. |
| * |
| * @param <T> the type of the values to be tested against predicates. |
| */ |
| public class Predicates<T> extends Guardrail |
| { |
| private final Function<ClientState, Predicate<T>> warnPredicate; |
| private final Function<ClientState, Predicate<T>> failurePredicate; |
| private final MessageProvider<T> messageProvider; |
| |
| /** |
| * A function used to build the warning or error message of a triggered {@link Predicates} guardrail. |
| */ |
| public interface MessageProvider<T> |
| { |
| /** |
| * Called when the guardrail is triggered to build the corresponding message. |
| * |
| * @param isWarning whether the trigger is a warning one; otherwise it is failure one. |
| * @param value the value that triggers guardrail. |
| */ |
| String createMessage(boolean isWarning, T value); |
| } |
| |
| /** |
| * Creates a new {@link Predicates} guardrail. |
| * |
| * @param name the identifying name of the guardrail |
| * @param reason the optional description of the reason for guarding the operation |
| * @param warnPredicate a {@link ClientState}-based predicate provider that is used to check if given value should trigger a warning. |
| * @param failurePredicate a {@link ClientState}-based predicate provider that is used to check if given value should trigger a failure. |
| * @param messageProvider a function to generate the warning or error message if the guardrail is triggered |
| */ |
| Predicates(String name, |
| @Nullable String reason, |
| Function<ClientState, Predicate<T>> warnPredicate, |
| Function<ClientState, Predicate<T>> failurePredicate, |
| MessageProvider<T> messageProvider) |
| { |
| super(name, reason); |
| this.warnPredicate = warnPredicate; |
| this.failurePredicate = failurePredicate; |
| this.messageProvider = messageProvider; |
| } |
| |
| /** |
| * Apply the guardrail to the provided value, triggering a warning or failure if appropriate. |
| * |
| * @param value the value to check. |
| */ |
| public void guard(T value, @Nullable ClientState state) |
| { |
| if (!enabled(state)) |
| return; |
| |
| if (failurePredicate.apply(state).test(value)) |
| { |
| fail(messageProvider.createMessage(false, value), state); |
| } |
| else if (warnPredicate.apply(state).test(value)) |
| { |
| warn(messageProvider.createMessage(true, value)); |
| } |
| } |
| } |