| /* |
| * 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.druid.query; |
| |
| import com.google.common.util.concurrent.ListenableFuture; |
| |
| /** |
| * This interface is in a very early stage and should not be considered stable. |
| * |
| * The purpose of the QueryWatcher is to give overall visibility into queries running |
| * or pending at the QueryRunner level. This is currently used to cancel all the |
| * parts of a pending query, but may be expanded in the future to offer more direct |
| * visibility into query execution and resource usage. |
| * |
| * QueryRunners executing any computation asynchronously must register their queries |
| * with the QueryWatcher. |
| * |
| */ |
| public interface QueryWatcher |
| { |
| /** |
| * QueryRunners must use this method to register any pending queries. |
| * |
| * The given future may have cancel(true) called at any time, if cancellation of this query has been requested. |
| * |
| * @param query a query, which may be a subset of a larger query, as long as the underlying queryId is unchanged |
| * @param future the future holding the execution status of the query |
| */ |
| void registerQueryFuture(Query<?> query, ListenableFuture<?> future); |
| } |