| /* |
| * Copyright (c) 2008, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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| */ |
| |
| /** |
| * This package provides a mechanism for defining and |
| * inserting tracepoints into Java-technology based applications, which |
| * can then be monitored by the tracing tools available on the system. |
| * <p> |
| * To add tracepoints to a program, you must first decide where to place the |
| * tracepoints, what the logical names are for these points, what information |
| * will be available to the tracing mechanisms at each point, and decide upon |
| * any logical grouping. |
| * <p> |
| * You add instrumentation to a program in three steps: |
| * <ul> |
| * <li>First, declare tracepoints by creating interfaces to define |
| * them, and include these interfaces in the program definition. |
| * The declared interfaces are standard Java technology-based |
| * interfaces and are compiled with the program.</li> |
| * <li>Second, add code in the application to create an instance of the |
| * interface at some point during the initialization of the application, |
| * using a factory class provided by the system. The reference to the |
| * instance can be stored as a global static, or passed as context to all |
| * the places where it is needed.</li> |
| * <li>Finally, add the actual tracepoints to the desired locations in the |
| * application by inserting a call to one of the methods defined in the |
| * interface, via the factory-created reference.</li> |
| * </ul> |
| * <p> |
| * The method calls representing the tracepoints have no logical |
| * impact on the program. The side effect of the call is that any |
| * activated tracing mechanisms will be notified that the tracepoint has |
| * been hit, and will take whatever actions are appropriate (for example, |
| * logging the tracepoint, or triggering a DTrace probe, etc.). In most |
| * cases, the impact on performance of adding tracepoints to the application |
| * will be minimal. |
| * <p> |
| * Each logical grouping of tracepoints should be defined in a common |
| * interface, called a <i>provider</i>. An application can have one or many |
| * providers. Each provider is independent and can be created whenever |
| * it is appropriate for that provider, for example, when a subsytem is |
| * initialized. Providers should be disposed of when they are no longer |
| * needed, to free up any associated system resources. Each tracepoint |
| * in a provider is represented by a method in that interface. These methods |
| * are referred to as <i>probes</i>. The method signature determines the probe |
| * parameters. A call to the method with the specified parameters triggers |
| * the probe and makes its parameter values visible to any associated tracing |
| * mechanism. |
| * <p> |
| * User-defined interfaces which represent providers must extend the |
| * {@code Provider} interface. To activate the system-defined |
| * tracing mechanisms, you must obtain an instance of the |
| * {@code ProviderFactory} class, and pass the class of the provider to |
| * the {@code createProvider()} method. The returned instance is then used to |
| * trigger the probes later in the application. |
| * <p> |
| * In addition to triggering the probes, the provider instance can be used |
| * to obtain direct references to the {@code Probe} objects, which can be used |
| * directly for triggering, or can be queried to determine whether the probe is |
| * currently being traced. The {@code Provider} interface also defines a |
| * {@code Provider.dispose()} method which is used to free up any resources |
| * that might be associated with that provider. |
| * <p> |
| * When a probe is triggered, any activated tracing system will be given |
| * the provider name, the probe name, and the values of the probe arguments. |
| * The tracing system is free to consume this data is whatever way is |
| * appropriate. |
| * By default, the provider name is the same as the class name of the interface |
| * that defines the provider. Similarly, the probe name is |
| * the name of the method that defines the probe. These default values |
| * can be over-ridden by annotations. The provider definition can be |
| * annotated with the {@code @ProviderName} annotation, whose value will |
| * indicate the provider name that the tracing system will use. Similarly, |
| * the {@code @ProbeName} annotation annotates a declared method and |
| * indicates the probe name that should be used in the place of the |
| * method name. These annotations can be used to define providers and |
| * probes with the same name, in cases where the semantics of the Java language |
| * may prevent this. |
| * <p> |
| * Here is a very small and simple usage example: |
| * <p> |
| * |
| <PRE> |
| import com.sun.tracing.Provider; |
| import com.sun.tracing.ProviderFactory; |
| |
| interface MyProvider extends Provider { |
| void startProbe(); |
| void finishProbe(int value); |
| } |
| |
| public class MyApplication { |
| public static void main(String argv[]) { |
| ProviderFactory factory = ProviderFactory.getDefaultFactory(); |
| MyProvider trace = factory.createProvider(MyProvider.class); |
| |
| trace.startProbe(); |
| int result = foo(); |
| trace.finishProbe(result); |
| |
| trace.dispose(); |
| } |
| } |
| </PRE> |
| * <p> |
| * The Java Development Kit (JDK) currently only includes one system-defined |
| * tracing framework: DTrace. DTrace is enabled automatically whenever an |
| * application is run on a system and a JDK release that supports it. When |
| * DTrace is enabled, probes are made available for listing and matching by |
| * DTrace scripts as soon as the provider is created. At the tracepoint, an |
| * associated DTrace script is informed of the creation of the provider, and |
| * it takes whatever action it is designed to take. Tracepoints in the |
| * program have the following DTrace probe names:<br> |
| * {@code <provider><pid>:<module>:<function>:<probe>} |
| * Where: |
| * <ul> |
| * <li>{@code <provider>} the provider name as specified by the application</li> |
| * <li>{@code <pid>} the operating system process ID</li> |
| * <li>{@code <module>} undefined, unless specified by the application</li> |
| * <li>{@code <function>} undefined, unless specified by the application</li> |
| * <li>{@code <probe>} the probe name as specified by the application</li> |
| * </ul> |
| * <p> |
| * The {@code com.sun.tracing.dtrace} package contains additional |
| * annotations that can be used to control the names used for the |
| * <code>module</code> and <code>function</code> fields, as well as annotations |
| * that can be added to the provider to control probe stability and dependency |
| * attributes. |
| * <p> |
| * Integer, float and string probe parameters are made available to DTrace |
| * using |
| * the built-in argument variables, {@code arg0 ... arg_n}. Integer-types |
| * are passed by value (boxed values are unboxed), floating-point types are |
| * passed as encoded integer |
| * arguments, and {@code java.lang.String} objects are converted |
| * to UTF8 strings, so they can be read into the DTrace script using the |
| * {@code copyinstr()} intrinsic. Non-string and non-boxed primitive |
| * reference arguments are only |
| * placeholders and have no value. |
| * <p> |
| * Using the example above, with a theoretical process ID of 123, these are |
| * the probes that can be traced from DTrace: |
| <PRE> |
| MyProvider123:::startProbe |
| MyProvider123:::finishProbe |
| </PRE> |
| * When {@code finishProbe} executes, {@code arg0} will contain the |
| * value of {@code result}. |
| * <p> |
| * The DTrace tracing mechanism is enabled for all providers, apart from in the |
| * following circumstances: |
| * <ul> |
| * <li>DTrace is not supported on the underlying system.</li> |
| * <li>The property {@code com.sun.tracing.dtrace} is set to "disable".</li> |
| * <li>The RuntimePermission {@code com.sun.tracing.dtrace.createProvider} |
| * is denied to the process.</li> |
| * </ul> |
| * <p> |
| */ |
| |
| package com.sun.tracing; |
