| /* |
| * 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.schema; |
| |
| import java.time.Duration; |
| |
| import org.apache.cassandra.schema.SchemaTransformation.SchemaTransformationResult; |
| import org.apache.cassandra.utils.concurrent.Awaitable; |
| |
| /** |
| * Schema update handler is responsible for maintaining the shared schema and synchronizing it with other nodes in |
| * the cluster, which means pushing and pulling changes, as well as tracking the current version in the cluster. |
| * <p/> |
| * The interface has been extracted to abstract out that functionality. It allows for various implementations like |
| * Gossip based (the default), ETCD, offline, etc., and make it easier for mocking in unit tests. |
| */ |
| public interface SchemaUpdateHandler |
| { |
| /** |
| * Starts actively synchronizing schema with the rest of the cluster. It is called in the very beginning of the |
| * node startup. It is not expected to block - to await for the startup completion we have another method |
| * {@link #waitUntilReady(Duration)}. |
| */ |
| void start(); |
| |
| /** |
| * Waits until the schema update handler is ready and returns the result. If the method returns {@code false} it |
| * means that readiness could not be achieved within the specified period of time. The method can be used just to |
| * check if schema is ready by passing {@link Duration#ZERO} as the timeout - in such case it returns immediately. |
| * |
| * @param timeout the maximum time to wait for schema readiness |
| * @return whether readiness is achieved |
| */ |
| boolean waitUntilReady(Duration timeout); |
| |
| /** |
| * Applies schema transformation in the underlying storage and synchronizes with other nodes. |
| * |
| * @param transformation schema transformation to be performed |
| * @param local if true, the caller does not require synchronizing schema with other nodes - in practise local is |
| * used only in some tests |
| * @return transformation result |
| */ |
| SchemaTransformationResult apply(SchemaTransformation transformation, boolean local); |
| |
| /** |
| * Resets the schema either by reloading data from the local storage or from the other nodes. Once the schema is |
| * refreshed, the callbacks provided in the factory method are executed, and the updated schema version is announced. |
| * |
| * @param local whether we should reset with locally stored schema or fetch the schema from other nodes |
| */ |
| void reset(boolean local); |
| |
| /** |
| * Marks the local schema to be cleared and refreshed. Since calling this method, the update handler tries to obtain |
| * a fresh schema definition from a remote source. Once the schema definition is received, the local schema is |
| * replaced (instead of being merged which usually happens when the update is received). |
| * <p/> |
| * The returned awaitable is fulfilled when the schema is received and applied. |
| */ |
| Awaitable clear(); |
| } |