AnalysisResult.java

/*
 * Copyright (C) 2015 Square, Inc.
 *
 * Licensed 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 com.android.chap04;

import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import java.io.Serializable;

public final class AnalysisResult implements Serializable {

    public static final long RETAINED_HEAP_SKIPPED = -1;

    public static @NonNull AnalysisResult noLeak(String className, long analysisDurationMs) {
        return new AnalysisResult(false, false, className, null, null, 0, analysisDurationMs);
    }

    public static @NonNull AnalysisResult leakDetected(boolean excludedLeak,
                                                       @NonNull String className,
                                                       @NonNull LeakTrace leakTrace, long retainedHeapSize, long analysisDurationMs) {
        return new AnalysisResult(true, excludedLeak, className, leakTrace, null, retainedHeapSize,
                analysisDurationMs);
    }

    public static @NonNull AnalysisResult failure(@NonNull Throwable failure,
                                                  long analysisDurationMs) {
        return new AnalysisResult(false, false, null, null, failure, 0, analysisDurationMs);
    }

    /** True if a leak was found in the heap dump. */
    public final boolean leakFound;

    /**
     * True if {@link #leakFound} is true and the only path to the leaking reference is
     * through excluded references. Usually, that means you can safely ignore this report.
     */
    public final boolean excludedLeak;

    /**
     * Class name of the object that leaked, null if {@link #failure} is not null.
     * The class name format is the same as what would be returned by {@link Class#getName()}.
     */
    @Nullable public final String className;

    /**
     * Shortest path to GC roots for the leaking object if {@link #leakFound} is true, null
     * otherwise. This can be used as a unique signature for the leak.
     */
    @Nullable public final LeakTrace leakTrace;

    /** Null unless the analysis failed. */
    @Nullable public final Throwable failure;

    /**
     * The number of bytes which would be freed if all references to the leaking object were
     * released. {@link #RETAINED_HEAP_SKIPPED} if the retained heap size was not computed. 0 if
     * {@link #leakFound} is false.
     */
    public final long retainedHeapSize;

    /** Total time spent analyzing the heap. */
    public final long analysisDurationMs;

    /**
     * <p>Creates a new {@link RuntimeException} with a fake stack trace that maps the leak trace.
     *
     * <p>Leak traces uniquely identify memory leaks, much like stack traces uniquely identify
     * exceptions.
     *
     * <p>This method enables you to upload leak traces as stack traces to your preferred
     * exception reporting tool and benefit from the grouping and counting these tools provide out
     * of the box. This also means you can track all leaks instead of relying on individuals
     * reporting them when they happen.
     *
     * <p>The following example leak trace:
     * <pre>
     * * com.foo.WibbleActivity has leaked:
     * * GC ROOT static com.foo.Bar.qux
     * * references com.foo.Quz.context
     * * leaks com.foo.WibbleActivity instance
     * </pre>
     *
     * <p>Will turn into an exception with the following stacktrace:
     * <pre>
     * java.lang.RuntimeException: com.foo.WibbleActivity leak from com.foo.Bar (holder=CLASS,
     * type=STATIC_FIELD)
     *         at com.foo.Bar.qux(Bar.java:42)
     *         at com.foo.Quz.context(Quz.java:42)
     *         at com.foo.WibbleActivity.leaking(WibbleActivity.java:42)
     * </pre>
     */
    public @NonNull RuntimeException leakTraceAsFakeException() {
        if (!leakFound) {
            throw new UnsupportedOperationException(
                    "leakTraceAsFakeException() can only be called when leakFound is true");
        }
        LeakTraceElement firstElement = leakTrace.elements.get(0);
        String rootSimpleName = classSimpleName(firstElement.className);
        String leakSimpleName = classSimpleName(className);

        String exceptionMessage = leakSimpleName
                + " leak from "
                + rootSimpleName
                + " (holder="
                + firstElement.holder
                + ", type="
                + firstElement.type
                + ")";
        RuntimeException exception = new RuntimeException(exceptionMessage);

        StackTraceElement[] stackTrace = new StackTraceElement[leakTrace.elements.size()];
        int i = 0;
        for (LeakTraceElement element : leakTrace.elements) {
            String methodName = element.referenceName != null ? element.referenceName : "leaking";
            String file = classSimpleName(element.className) + ".java";
            stackTrace[i] = new StackTraceElement(element.className, methodName, file, 42);
            i++;
        }
        exception.setStackTrace(stackTrace);
        return exception;
    }

    private AnalysisResult(boolean leakFound, boolean excludedLeak, String className,
                           LeakTrace leakTrace, Throwable failure, long retainedHeapSize, long analysisDurationMs) {
        this.leakFound = leakFound;
        this.excludedLeak = excludedLeak;
        this.className = className;
        this.leakTrace = leakTrace;
        this.failure = failure;
        this.retainedHeapSize = retainedHeapSize;
        this.analysisDurationMs = analysisDurationMs;
    }

    private String classSimpleName(String className) {
        int separator = className.lastIndexOf('.');
        return separator == -1 ? className : className.substring(separator + 1);
    }
}