| /* |
| * 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.diag.store; |
| |
| import java.util.Comparator; |
| import java.util.Map; |
| import java.util.NavigableMap; |
| import java.util.concurrent.ConcurrentNavigableMap; |
| import java.util.concurrent.ConcurrentSkipListMap; |
| import java.util.concurrent.atomic.AtomicLong; |
| |
| import com.google.common.annotations.VisibleForTesting; |
| |
| import org.apache.cassandra.diag.DiagnosticEvent; |
| |
| /** |
| * Simple on-heap memory store that allows to buffer and retrieve a fixed number of events. |
| */ |
| public final class DiagnosticEventMemoryStore implements DiagnosticEventStore<Long> |
| { |
| private final AtomicLong lastKey = new AtomicLong(0); |
| |
| private int maxSize = 200; |
| |
| // event access will mostly happen based on a recent event offset, so we add new events to the head of the list |
| // for optimized search times |
| private final ConcurrentSkipListMap<Long, DiagnosticEvent> events = new ConcurrentSkipListMap<>(Comparator.reverseOrder()); |
| |
| public void load() |
| { |
| // no-op |
| } |
| |
| public void store(DiagnosticEvent event) |
| { |
| long keyHead = lastKey.incrementAndGet(); |
| events.put(keyHead, event); |
| |
| // remove elements starting exceeding max size |
| if (keyHead > maxSize) events.tailMap(keyHead - maxSize).clear(); |
| } |
| |
| public NavigableMap<Long, DiagnosticEvent> scan(Long id, int limit) |
| { |
| assert id != null && id >= 0; |
| assert limit >= 0; |
| |
| // [10..1].headMap(2, false): [10..3] |
| ConcurrentNavigableMap<Long, DiagnosticEvent> newerEvents = events.headMap(id, true); |
| // [3..10] |
| ConcurrentNavigableMap<Long, DiagnosticEvent> ret = newerEvents.descendingMap(); |
| if (limit == 0) |
| { |
| return ret; |
| } |
| else |
| { |
| Map.Entry<Long, DiagnosticEvent> first = ret.firstEntry(); |
| if (first == null) return ret; |
| else return ret.headMap(first.getKey() + limit); |
| } |
| } |
| |
| public Long getLastEventId() |
| { |
| return lastKey.get(); |
| } |
| |
| @VisibleForTesting |
| int size() |
| { |
| return events.size(); |
| } |
| |
| @VisibleForTesting |
| void setMaxSize(int maxSize) |
| { |
| this.maxSize = maxSize; |
| } |
| |
| } |