/core/src/main/java/hudson/ExtensionFinder.java
Java | 454 lines | 256 code | 42 blank | 156 comment | 21 complexity | 19a4880df73e52290f792f89393a9e5c MD5 | raw file
- /*
- * The MIT License
- *
- * Copyright (c) 2004-2010, Sun Microsystems, Inc., InfraDNA, Inc., CloudBees, Inc.
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
- package hudson;
- import com.google.inject.AbstractModule;
- import com.google.inject.Binding;
- import com.google.inject.CreationException;
- import com.google.inject.Guice;
- import com.google.inject.Injector;
- import com.google.inject.Key;
- import com.google.inject.Module;
- import com.google.inject.Provider;
- import com.google.inject.Scope;
- import com.google.inject.Scopes;
- import com.google.inject.name.Names;
- import com.google.common.collect.ImmutableList;
- import hudson.init.InitMilestone;
- import hudson.model.Descriptor;
- import hudson.model.Hudson;
- import jenkins.model.Jenkins;
- import net.java.sezpoz.Index;
- import net.java.sezpoz.IndexItem;
- import org.kohsuke.accmod.Restricted;
- import org.kohsuke.accmod.restrictions.NoExternalUse;
- import java.lang.annotation.Annotation;
- import java.util.Collections;
- import java.util.HashMap;
- import java.util.Map;
- import java.util.Map.Entry;
- import java.util.logging.Logger;
- import java.util.logging.Level;
- import java.util.List;
- import java.util.ArrayList;
- import java.util.Collection;
- import java.lang.reflect.AnnotatedElement;
- import java.lang.reflect.Field;
- import java.lang.reflect.Method;
- /**
- * Discovers the implementations of an extension point.
- *
- * <p>
- * This extension point allows you to write your implementations of {@link ExtensionPoint}s
- * in arbitrary DI containers, and have Hudson discover them.
- *
- * <p>
- * {@link ExtensionFinder} itself is an extension point, but to avoid infinite recursion,
- * Hudson discovers {@link ExtensionFinder}s through {@link Sezpoz} and that alone.
- *
- * @author Kohsuke Kawaguchi
- * @since 1.286
- */
- public abstract class ExtensionFinder implements ExtensionPoint {
- /**
- * @deprecated as of 1.356
- * Use and implement {@link #find(Class,Hudson)} that allows us to put some metadata.
- */
- @Restricted(NoExternalUse.class)
- public <T> Collection<T> findExtensions(Class<T> type, Hudson hudson) {
- return Collections.emptyList();
- }
- /**
- * Discover extensions of the given type.
- *
- * <p>
- * This method is called only once per the given type after all the plugins are loaded,
- * so implementations need not worry about caching.
- *
- * @param <T>
- * The type of the extension points. This is not bound to {@link ExtensionPoint} because
- * of {@link Descriptor}, which by itself doesn't implement {@link ExtensionPoint} for
- * a historical reason.
- * @param hudson
- * Hudson whose behalf this extension finder is performing lookup.
- * @return
- * Can be empty but never null.
- * @since 1.356
- * Older implementations provide {@link #findExtensions(Class,Hudson)}
- */
- public abstract <T> Collection<ExtensionComponent<T>> find(Class<T> type, Hudson hudson);
- /**
- * A pointless function to work around what appears to be a HotSpot problem. See JENKINS-5756 and bug 6933067
- * on BugParade for more details.
- */
- public <T> Collection<ExtensionComponent<T>> _find(Class<T> type, Hudson hudson) {
- return find(type,hudson);
- }
- /**
- * Performs class initializations without creating instances.
- *
- * If two threads try to initialize classes in the opposite order, a dead lock will ensue,
- * and we can get into a similar situation with {@link ExtensionFinder}s.
- *
- * <p>
- * That is, one thread can try to list extensions, which results in {@link ExtensionFinder}
- * loading and initializing classes. This happens inside a context of a lock, so that
- * another thread that tries to list the same extensions don't end up creating different
- * extension instances. So this activity locks extension list first, then class initialization next.
- *
- * <p>
- * In the mean time, another thread can load and initialize a class, and that initialization
- * can eventually results in listing up extensions, for example through static initializer.
- * Such activity locks class initialization first, then locks extension list.
- *
- * <p>
- * This inconsistent locking order results in a dead lock, you see.
- *
- * <p>
- * So to reduce the likelihood, this method is called in prior to {@link #find(Class,Hudson)} invocation,
- * but from outside the lock. The implementation is expected to perform all the class initialization activities
- * from here.
- *
- * <p>
- * See http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6459208 for how to force a class initialization.
- * Also see http://kohsuke.org/2010/09/01/deadlock-that-you-cant-avoid/ for how class initialization
- * can results in a dead lock.
- */
- public void scout(Class extensionType, Hudson hudson) {
- }
- @Extension
- public static final class GuiceFinder extends AbstractGuiceFinder<Extension> {
- public GuiceFinder() {
- super(Extension.class);
- }
- @Override
- protected boolean isOptional(Extension annotation) {
- return annotation.optional();
- }
- @Override
- protected double getOrdinal(Extension annotation) {
- return annotation.ordinal();
- }
- }
- /**
- * Discovers components via sezpoz but instantiates them by using Guice.
- */
- public static abstract class AbstractGuiceFinder<T extends Annotation> extends ExtensionFinder {
- private Injector container;
- private final Map<Key,T> annotations = new HashMap<Key,T>();
- public AbstractGuiceFinder(final Class<T> annotationType) {
- List<Module> modules = new ArrayList<Module>();
- modules.add(new SezpozModule(annotationType,Jenkins.getInstance().getPluginManager().uberClassLoader));
- for (ExtensionComponent<Module> ec : new Sezpoz().find(Module.class, Hudson.getInstance())) {
- modules.add(ec.getInstance());
- }
- try {
- container = Guice.createInjector(modules);
- } catch (CreationException e) {
- LOGGER.log(Level.SEVERE, "Failed to create Guice container from all the plugins",e);
- // failing to load all bindings are disastrous, so recover by creating minimum that works
- // by just including the core
- container = Guice.createInjector(new SezpozModule(annotationType,Jenkins.class.getClassLoader()));
- }
- }
- protected abstract double getOrdinal(T annotation);
- /**
- * Hook to enable subtypes to control which ones to pick up and which ones to ignore.
- */
- protected boolean isActive(AnnotatedElement e) {
- return true;
- }
- protected abstract boolean isOptional(T annotation);
- private Object instantiate(IndexItem<T,Object> item) {
- try {
- return item.instance();
- } catch (LinkageError e) {
- // sometimes the instantiation fails in an indirect classloading failure,
- // which results in a LinkageError
- LOGGER.log(isOptional(item.annotation()) ? Level.FINE : Level.WARNING,
- "Failed to load "+item.className(), e);
- } catch (InstantiationException e) {
- LOGGER.log(isOptional(item.annotation()) ? Level.FINE : Level.WARNING,
- "Failed to load "+item.className(), e);
- }
- return null;
- }
- public <U> Collection<ExtensionComponent<U>> find(Class<U> type, Hudson hudson) {
- List<ExtensionComponent<U>> result = new ArrayList<ExtensionComponent<U>>();
- for (Entry<Key<?>, Binding<?>> e : container.getBindings().entrySet()) {
- if (type.isAssignableFrom(e.getKey().getTypeLiteral().getRawType())) {
- T a = annotations.get(e.getKey());
- Object o = e.getValue().getProvider().get();
- if (o!=null)
- result.add(new ExtensionComponent<U>(type.cast(o),a!=null?getOrdinal(a):0));
- }
- }
- return result;
- }
- /**
- * TODO: need to learn more about concurrent access to {@link Injector} and how it interacts
- * with classloading.
- */
- @Override
- public void scout(Class extensionType, Hudson hudson) {
- }
- /**
- * {@link Scope} that allows a failure to create a component,
- * and change the value to null.
- *
- * <p>
- * This is necessary as a failure to load one plugin shouldn't fail the startup of the entire Jenkins.
- * Instead, we should just drop the failing plugins.
- */
- public static final Scope FAULT_TOLERANT_SCOPE = new Scope() {
- public <T> Provider<T> scope(Key<T> key, Provider<T> unscoped) {
- final Provider<T> base = Scopes.SINGLETON.scope(key,unscoped);
- return new Provider<T>() {
- public T get() {
- try {
- return base.get();
- } catch (Exception e) {
- LOGGER.log(Level.WARNING,"Failed to instantiate",e);
- return null;
- }
- }
- };
- }
- };
- private static final Logger LOGGER = Logger.getLogger(GuiceFinder.class.getName());
- private class SezpozModule extends AbstractModule {
- private final Class<T> annotationType;
- private final ClassLoader cl;
- public SezpozModule(Class<T> annotationType, ClassLoader cl) {
- this.annotationType = annotationType;
- this.cl = cl;
- }
- /**
- * Guice performs various reflection operations on the class to figure out the dependency graph,
- * and that process can cause additional classloading problems, which will fail the injector creation,
- * which in turn has disastrous effect on the startup.
- *
- * <p>
- * Ultimately I'd like to isolate problems to plugins and selectively disable them, allowing
- * Jenkins to start with plugins that work, but I haven't figured out how.
- *
- * So this is an attempt to detect subset of problems eagerly, by invoking various reflection
- * operations and try to find non-existent classes early.
- */
- private void resolve(Class c) {
- try {
- c.getGenericSuperclass();
- c.getGenericInterfaces();
- ClassLoader ecl = c.getClassLoader();
- Method m = ClassLoader.class.getDeclaredMethod("resolveClass", Class.class);
- m.setAccessible(true);
- m.invoke(ecl, c);
- } catch (Exception x) {
- throw (LinkageError)new LinkageError("Failed to resolve "+c).initCause(x);
- }
- }
- @SuppressWarnings({"unchecked", "ChainOfInstanceofChecks"})
- @Override
- protected void configure() {
- int id=0;
- for (final IndexItem<T,Object> item : Index.load(annotationType, Object.class, cl)) {
- id++;
- try {
- AnnotatedElement e = item.element();
- if (!isActive(e)) continue;
- T a = item.annotation();
- if (e instanceof Class) {
- Key key = Key.get((Class)e);
- resolve((Class)e);
- annotations.put(key,a);
- bind(key).in(FAULT_TOLERANT_SCOPE);
- } else {
- Class extType;
- if (e instanceof Field) {
- extType = ((Field)e).getType();
- } else
- if (e instanceof Method) {
- extType = ((Method)e).getReturnType();
- } else
- throw new AssertionError();
- resolve(extType);
- // use arbitrary id to make unique key, because Guice wants that.
- Key key = Key.get(extType, Names.named(String.valueOf(id)));
- annotations.put(key,a);
- bind(key).toProvider(new Provider() {
- public Object get() {
- return instantiate(item);
- }
- }).in(FAULT_TOLERANT_SCOPE);
- }
- } catch (LinkageError e) {
- // sometimes the instantiation fails in an indirect classloading failure,
- // which results in a LinkageError
- LOGGER.log(isOptional(item.annotation()) ? Level.FINE : Level.WARNING,
- "Failed to load "+item.className(), e);
- } catch (InstantiationException e) {
- LOGGER.log(isOptional(item.annotation()) ? Level.FINE : Level.WARNING,
- "Failed to load "+item.className(), e);
- }
- }
- }
- }
- }
- /**
- * The bootstrap implementation that looks for the {@link Extension} marker.
- *
- * <p>
- * Uses Sezpoz as the underlying mechanism.
- */
- public static final class Sezpoz extends ExtensionFinder {
- private volatile List<IndexItem<Extension,Object>> indices;
- /**
- * Loads indices (ideally once but as few times as possible), then reuse them later.
- * {@link ExtensionList#ensureLoaded()} guarantees that this method won't be called until
- * {@link InitMilestone#PLUGINS_PREPARED} is attained, so this method is guaranteed to
- * see all the classes and indices.
- */
- private List<IndexItem<Extension,Object>> getIndices() {
- // this method cannot be synchronized because of a dead lock possibility in the following order of events:
- // 1. thread X can start listing indices, locking this object 'SZ'
- // 2. thread Y starts loading a class, locking a classloader 'CL'
- // 3. thread X needs to load a class, now blocked on CL
- // 4. thread Y decides to load extensions, now blocked on SZ.
- // 5. dead lock
- if (indices==null) {
- ClassLoader cl = Jenkins.getInstance().getPluginManager().uberClassLoader;
- indices = ImmutableList.copyOf(Index.load(Extension.class, Object.class, cl));
- }
- return indices;
- }
- public <T> Collection<ExtensionComponent<T>> find(Class<T> type, Hudson hudson) {
- List<ExtensionComponent<T>> result = new ArrayList<ExtensionComponent<T>>();
- for (IndexItem<Extension,Object> item : getIndices()) {
- try {
- AnnotatedElement e = item.element();
- Class<?> extType;
- if (e instanceof Class) {
- extType = (Class) e;
- } else
- if (e instanceof Field) {
- extType = ((Field)e).getType();
- } else
- if (e instanceof Method) {
- extType = ((Method)e).getReturnType();
- } else
- throw new AssertionError();
- if(type.isAssignableFrom(extType)) {
- Object instance = item.instance();
- if(instance!=null)
- result.add(new ExtensionComponent<T>(type.cast(instance),item.annotation()));
- }
- } catch (LinkageError e) {
- // sometimes the instantiation fails in an indirect classloading failure,
- // which results in a LinkageError
- LOGGER.log(logLevel(item), "Failed to load "+item.className(), e);
- } catch (InstantiationException e) {
- LOGGER.log(logLevel(item), "Failed to load "+item.className(), e);
- }
- }
- return result;
- }
- @Override
- public void scout(Class extensionType, Hudson hudson) {
- for (IndexItem<Extension,Object> item : getIndices()) {
- try {
- // we might end up having multiple threads concurrently calling into element(),
- // but we can't synchronize this --- if we do, the one thread that's supposed to load a class
- // can block while other threads wait for the entry into the element call().
- // looking at the sezpoz code, it should be safe to do so
- AnnotatedElement e = item.element();
- Class<?> extType;
- if (e instanceof Class) {
- extType = (Class) e;
- } else
- if (e instanceof Field) {
- extType = ((Field)e).getType();
- } else
- if (e instanceof Method) {
- extType = ((Method)e).getReturnType();
- } else
- throw new AssertionError();
- // according to http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6459208
- // this appears to be the only way to force a class initialization
- Class.forName(extType.getName(),true,extType.getClassLoader());
- } catch (InstantiationException e) {
- LOGGER.log(logLevel(item), "Failed to scout "+item.className(), e);
- } catch (ClassNotFoundException e) {
- LOGGER.log(logLevel(item), "Failed to scout "+item.className(), e);
- } catch (LinkageError e) {
- LOGGER.log(logLevel(item), "Failed to scout "+item.className(), e);
- }
- }
- }
- private Level logLevel(IndexItem<Extension, Object> item) {
- return item.annotation().optional() ? Level.FINE : Level.WARNING;
- }
- }
- private static final Logger LOGGER = Logger.getLogger(ExtensionFinder.class.getName());
- }