| 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.context; |
| 9 | |
| 10 | import java.io.IOException; |
| 11 | import java.util.HashMap; |
| 12 | import java.util.Map; |
| 13 | import java.util.concurrent.ConcurrentHashMap; |
| 14 | import java.util.regex.Matcher; |
| 15 | import java.util.regex.Pattern; |
| 16 | |
| 17 | /** |
| 18 | * The singleton manager of {@link IContextInfoRetriever} objects. |
| 19 | * |
| 20 | * @author Alexandre Montplaisir |
| 21 | */ |
| 22 | public final class ContextInfoManager { |
| 23 | |
| 24 | private static final String SHARED_LIBRARY_NAME = "lttng-ust-context-jni"; |
| 25 | |
| 26 | private static final Pattern VALID_CONTEXT_NAME_PATTERN = Pattern.compile("^[a-zA-Z0-9_\\.]+$"); |
| 27 | |
| 28 | private static ContextInfoManager instance; |
| 29 | |
| 30 | private final Map<String, IContextInfoRetriever> contextInfoRetrievers = new ConcurrentHashMap<String, IContextInfoRetriever>(); |
| 31 | private final Map<String, Long> contextInforRetrieverRefs = new HashMap<String, Long>(); |
| 32 | |
| 33 | /** |
| 34 | * Lock used to keep the two maps above in sync when retrievers are |
| 35 | * registered or unregistered. |
| 36 | */ |
| 37 | private final Object retrieverLock = new Object(); |
| 38 | |
| 39 | /** Singleton class, constructor should not be accessed directly */ |
| 40 | private ContextInfoManager() { |
| 41 | } |
| 42 | |
| 43 | /** |
| 44 | * Get the singleton instance. |
| 45 | * |
| 46 | * <p> |
| 47 | * Usage of this class requires the "liblttng-ust-context-jni.so" native |
| 48 | * library to be present on the system and available (passing |
| 49 | * -Djava.library.path=path to the JVM may be needed). |
| 50 | * </p> |
| 51 | * |
| 52 | * @return The singleton instance |
| 53 | * @throws IOException |
| 54 | * If the shared library cannot be found. |
| 55 | * @throws SecurityException |
| 56 | * We will forward any SecurityExcepion that may be thrown when |
| 57 | * trying to load the JNI library. |
| 58 | */ |
| 59 | public static synchronized ContextInfoManager getInstance() throws IOException, SecurityException { |
| 60 | if (instance == null) { |
| 61 | try { |
| 62 | System.loadLibrary(SHARED_LIBRARY_NAME); |
| 63 | } catch (UnsatisfiedLinkError e) { |
| 64 | throw new IOException(e); |
| 65 | } |
| 66 | instance = new ContextInfoManager(); |
| 67 | } |
| 68 | return instance; |
| 69 | } |
| 70 | |
| 71 | /** |
| 72 | * Register a new context info retriever. |
| 73 | * |
| 74 | * <p> |
| 75 | * Each context info retriever is registered with a given "retriever name", |
| 76 | * which specifies the namespace of the context elements. This name is |
| 77 | * specified separately from the retriever objects, which would allow |
| 78 | * register the same retriever under different namespaces for example. |
| 79 | * </p> |
| 80 | * |
| 81 | * <p> |
| 82 | * If the method returns false (indicating registration failure), then the |
| 83 | * retriever object will *not* be used for context information. |
| 84 | * </p> |
| 85 | * |
| 86 | * @param retrieverName |
| 87 | * The name to register to the context retriever object with. |
| 88 | * @param contextInfoRetriever |
| 89 | * The context info retriever to register |
| 90 | * @return True if the retriever was successfully registered, false if there |
| 91 | * was an error, for example if a retriever is already registered |
| 92 | * with that name. |
| 93 | */ |
| 94 | public boolean registerContextInfoRetriever(String retrieverName, IContextInfoRetriever contextInfoRetriever) { |
| 95 | synchronized (retrieverLock) { |
| 96 | if (!validateRetrieverName(retrieverName)) { |
| 97 | return false; |
| 98 | } |
| 99 | |
| 100 | if (contextInfoRetrievers.containsKey(retrieverName)) { |
| 101 | /* |
| 102 | * There is already a retriever registered with that name, |
| 103 | * refuse the new registration. |
| 104 | */ |
| 105 | return false; |
| 106 | } |
| 107 | /* |
| 108 | * Inform LTTng-UST of the new retriever. The names have to start |
| 109 | * with "$app." on the UST side! |
| 110 | */ |
| 111 | long ref = LttngContextApi.registerProvider("$app." + retrieverName); |
| 112 | if (ref == 0) { |
| 113 | return false; |
| 114 | } |
| 115 | |
| 116 | contextInfoRetrievers.put(retrieverName, contextInfoRetriever); |
| 117 | contextInforRetrieverRefs.put(retrieverName, Long.valueOf(ref)); |
| 118 | |
| 119 | return true; |
| 120 | } |
| 121 | } |
| 122 | |
| 123 | /** |
| 124 | * Unregister a previously added context info retriever. |
| 125 | * |
| 126 | * This method has no effect if the retriever was not already registered. |
| 127 | * |
| 128 | * @param retrieverName |
| 129 | * The context info retriever to unregister |
| 130 | * @return True if unregistration was successful, false if there was an |
| 131 | * error |
| 132 | */ |
| 133 | public boolean unregisterContextInfoRetriever(String retrieverName) { |
| 134 | synchronized (retrieverLock) { |
| 135 | if (!contextInfoRetrievers.containsKey(retrieverName)) { |
| 136 | /* |
| 137 | * There was no retriever registered with that name. |
| 138 | */ |
| 139 | return false; |
| 140 | } |
| 141 | contextInfoRetrievers.remove(retrieverName); |
| 142 | long ref = contextInforRetrieverRefs.remove(retrieverName).longValue(); |
| 143 | |
| 144 | /* Unregister the retriever on the UST side too */ |
| 145 | LttngContextApi.unregisterProvider(ref); |
| 146 | |
| 147 | return true; |
| 148 | } |
| 149 | } |
| 150 | |
| 151 | /** |
| 152 | * Return the context info retriever object registered with the given name. |
| 153 | * |
| 154 | * @param retrieverName |
| 155 | * The retriever name to look for |
| 156 | * @return The corresponding retriever object, or <code>null</code> if there |
| 157 | * was none |
| 158 | */ |
| 159 | public IContextInfoRetriever getContextInfoRetriever(String retrieverName) { |
| 160 | /* |
| 161 | * Note that this method does not take the retrieverLock, it lets |
| 162 | * concurrent threads access the ConcurrentHashMap directly. |
| 163 | * |
| 164 | * It's fine for a get() to happen during a registration or |
| 165 | * unregistration, it's first-come-first-serve. |
| 166 | */ |
| 167 | return contextInfoRetrievers.get(retrieverName); |
| 168 | } |
| 169 | |
| 170 | /** |
| 171 | * Validate that the given retriever name contains only the allowed |
| 172 | * characters, which are alphanumerical characters, period "." and |
| 173 | * underscore "_". The name must also not start with a number. |
| 174 | */ |
| 175 | private static boolean validateRetrieverName(String contextName) { |
| 176 | if (contextName.isEmpty()) { |
| 177 | return false; |
| 178 | } |
| 179 | |
| 180 | /* First character must not be a number */ |
| 181 | if (Character.isDigit(contextName.charAt(0))) { |
| 182 | return false; |
| 183 | } |
| 184 | |
| 185 | /* Validate the other characters of the string */ |
| 186 | Matcher matcher = VALID_CONTEXT_NAME_PATTERN.matcher(contextName); |
| 187 | return matcher.matches(); |
| 188 | } |
| 189 | } |