| 1 | /* |
| 2 | * SPDX-License-Identifier: LGPL-2.1-only |
| 3 | * |
| 4 | * Copyright (C) 2015 EfficiOS Inc. |
| 5 | * Copyright (C) 2015 Alexandre Montplaisir <alexmonthy@efficios.com> |
| 6 | */ |
| 7 | |
| 8 | package org.lttng.ust.agent.filter; |
| 9 | |
| 10 | import java.util.Collection; |
| 11 | import java.util.HashMap; |
| 12 | import java.util.LinkedList; |
| 13 | import java.util.List; |
| 14 | import java.util.Map; |
| 15 | |
| 16 | import org.lttng.ust.agent.session.EventRule; |
| 17 | |
| 18 | /** |
| 19 | * Singleton class managing the filter notifications. |
| 20 | * |
| 21 | * Applications can register a {@link IFilterChangeListener} to be notified when |
| 22 | * event filtering rules change in the tracing sessions. |
| 23 | * |
| 24 | * @author Alexandre Montplaisir |
| 25 | */ |
| 26 | public final class FilterChangeNotifier { |
| 27 | |
| 28 | /** Lazy-loaded singleton instance object */ |
| 29 | private static FilterChangeNotifier instance = null; |
| 30 | |
| 31 | private final Map<EventRule, Integer> enabledEventRules = new HashMap<EventRule, Integer>(); |
| 32 | private final Collection<IFilterChangeListener> registeredListeners = new LinkedList<IFilterChangeListener>(); |
| 33 | |
| 34 | |
| 35 | /** |
| 36 | * Private constructor, singleton class should not be instantiated directly. |
| 37 | */ |
| 38 | private FilterChangeNotifier() { |
| 39 | } |
| 40 | |
| 41 | /** |
| 42 | * Get the singleton instance, initializing it if needed. |
| 43 | * |
| 44 | * @return The singleton instance |
| 45 | */ |
| 46 | public static synchronized FilterChangeNotifier getInstance() { |
| 47 | if (instance == null) { |
| 48 | instance = new FilterChangeNotifier(); |
| 49 | } |
| 50 | return instance; |
| 51 | } |
| 52 | |
| 53 | /** |
| 54 | * Notify the filter manager that a new rule was enabled in a tracing |
| 55 | * session ("lttng enable-event ...") |
| 56 | * |
| 57 | * This is meant to be called by the LTTng Agent only. External Java |
| 58 | * applications should not call this. |
| 59 | * |
| 60 | * @param rule |
| 61 | * The rule that was added |
| 62 | */ |
| 63 | public synchronized void addEventRule(EventRule rule) { |
| 64 | Integer count = enabledEventRules.get(rule); |
| 65 | if (count == null) { |
| 66 | /* |
| 67 | * This is the first instance of this rule being enabled. Add it to |
| 68 | * the map and send notifications to the registered notifiers. |
| 69 | */ |
| 70 | enabledEventRules.put(rule, Integer.valueOf(1)); |
| 71 | notifyForAddedRule(rule); |
| 72 | return; |
| 73 | } |
| 74 | if (count.intValue() <= 0) { |
| 75 | /* It should not have been in the map! */ |
| 76 | throw new IllegalStateException(); |
| 77 | } |
| 78 | /* |
| 79 | * This exact event rule was already enabled, just increment its |
| 80 | * refcount without sending notifications |
| 81 | */ |
| 82 | enabledEventRules.put(rule, Integer.valueOf(count.intValue() + 1)); |
| 83 | } |
| 84 | |
| 85 | /** |
| 86 | * Notify the filter manager that an event name was disabled in the tracing |
| 87 | * sessions ("lttng disable-event ..."). |
| 88 | * |
| 89 | * The "disable-event" only specifies an event name. This means all the |
| 90 | * rules containing this event name are to be disabled. |
| 91 | * |
| 92 | * This is meant to be called by the LTTng Agent only. External Java |
| 93 | * applications should not call this. |
| 94 | * |
| 95 | * @param eventName |
| 96 | * The event name to disable |
| 97 | */ |
| 98 | public synchronized void removeEventRules(String eventName) { |
| 99 | List<EventRule> rulesToRemove = new LinkedList<EventRule>(); |
| 100 | |
| 101 | for (EventRule eventRule : enabledEventRules.keySet()) { |
| 102 | if (eventRule.getEventName().equals(eventName)) { |
| 103 | rulesToRemove.add(eventRule); |
| 104 | } |
| 105 | } |
| 106 | /* |
| 107 | * We cannot modify the map while iterating on it. We have to do the |
| 108 | * removal separately from the iteration above. |
| 109 | */ |
| 110 | for (EventRule rule : rulesToRemove) { |
| 111 | removeEventRule(rule); |
| 112 | } |
| 113 | } |
| 114 | |
| 115 | private synchronized void removeEventRule(EventRule eventRule) { |
| 116 | Integer count = enabledEventRules.get(eventRule); |
| 117 | if (count == null || count.intValue() <= 0) { |
| 118 | /* |
| 119 | * We were asked us to disable an event rule that was not enabled |
| 120 | * previously. Command error? |
| 121 | */ |
| 122 | throw new IllegalStateException(); |
| 123 | } |
| 124 | if (count.intValue() == 1) { |
| 125 | /* |
| 126 | * This is the last instance of this event rule being disabled, |
| 127 | * remove it from the map and send notifications of this rule being |
| 128 | * gone. |
| 129 | */ |
| 130 | enabledEventRules.remove(eventRule); |
| 131 | notifyForRemovedRule(eventRule); |
| 132 | return; |
| 133 | } |
| 134 | /* |
| 135 | * Other sessions/daemons are still looking for this event rule, simply |
| 136 | * decrement its refcount, and do not send notifications. |
| 137 | */ |
| 138 | enabledEventRules.put(eventRule, Integer.valueOf(count.intValue() - 1)); |
| 139 | |
| 140 | } |
| 141 | |
| 142 | /** |
| 143 | * Register a new listener to the manager. |
| 144 | * |
| 145 | * @param listener |
| 146 | * The listener to add |
| 147 | */ |
| 148 | public synchronized void registerListener(IFilterChangeListener listener) { |
| 149 | registeredListeners.add(listener); |
| 150 | |
| 151 | /* Send the current rules to the new listener ("statedump") */ |
| 152 | for (EventRule rule : enabledEventRules.keySet()) { |
| 153 | listener.eventRuleAdded(rule); |
| 154 | } |
| 155 | } |
| 156 | |
| 157 | /** |
| 158 | * Unregister a listener from the manager. |
| 159 | * |
| 160 | * @param listener |
| 161 | * The listener to remove |
| 162 | */ |
| 163 | public synchronized void unregisterListener(IFilterChangeListener listener) { |
| 164 | registeredListeners.remove(listener); |
| 165 | } |
| 166 | |
| 167 | private void notifyForAddedRule(final EventRule rule) { |
| 168 | for (IFilterChangeListener notifier : registeredListeners) { |
| 169 | notifier.eventRuleAdded(rule); |
| 170 | } |
| 171 | } |
| 172 | |
| 173 | private void notifyForRemovedRule(final EventRule rule) { |
| 174 | for (IFilterChangeListener notifier : registeredListeners) { |
| 175 | notifier.eventRuleRemoved(rule); |
| 176 | } |
| 177 | } |
| 178 | } |