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/*
 * Copyright 2013-2015 the original author or authors.
 *
 * 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 org.glowroot.jvm;

import java.lang.management.ManagementFactory;
import java.lang.reflect.Method;

import javax.annotation.Nullable;

import org.glowroot.shaded.google.common.annotations.VisibleForTesting;
import org.glowroot.shaded.slf4j.Logger;
import org.glowroot.shaded.slf4j.LoggerFactory;

import org.glowroot.common.Reflections;

public class ThreadAllocatedBytes {

    private static final Logger logger = LoggerFactory.getLogger(ThreadAllocatedBytes.class);

    private final Method getThreadAllocatedBytesMethod;
    private volatile boolean disabledDueToError;

    static OptionalService create() {
        try {
            return createInternal();
        } catch (Exception e) {
            logger.error(e.getMessage(), e);
            return OptionalService.unavailable("");
        }
    }

    private static OptionalService createInternal() throws Exception {
        Class sunThreadMXBeanClass;
        try {
            sunThreadMXBeanClass = Class.forName("com.sun.management.ThreadMXBean");
        } catch (ClassNotFoundException e) {
            // log exception at debug level
            logger.debug(e.getMessage(), e);
            return OptionalService.unavailable("Cannot find class com.sun.management.ThreadMXBean"
                    + " (introduced in Oracle Java SE 6u25)");
        }
        Method isSupportedMethod =
                Reflections.getMethod(sunThreadMXBeanClass, "isThreadAllocatedMemorySupported");
        Boolean supported = (Boolean) Reflections.invoke(isSupportedMethod,
                ManagementFactory.getThreadMXBean());
        return createInternal(supported, sunThreadMXBeanClass);
    }

    @VisibleForTesting
    static OptionalService createInternal(@Nullable Boolean supported,
            Class sunThreadMXBeanClass) throws Exception {
        if (supported == null) {
            return OptionalService.unavailable(
                    "ThreadMXBean.isThreadAllocatedMemorySupported() unexpectedly returned null");
        }
        if (!supported) {
            return OptionalService.unavailable("Method com.sun.management.ThreadMXBean"
                    + ".isThreadAllocatedMemorySupported() returned false");
        }
        Method getThreadAllocatedBytesMethod =
                Reflections.getMethod(sunThreadMXBeanClass, "getThreadAllocatedBytes", long.class);
        return OptionalService.available(new ThreadAllocatedBytes(getThreadAllocatedBytesMethod));
    }

    private ThreadAllocatedBytes(Method getThreadAllocatedBytesMethod) {
        this.getThreadAllocatedBytesMethod = getThreadAllocatedBytesMethod;
    }

    public long getThreadAllocatedBytesSafely(long threadId) {
        if (disabledDueToError) {
            // prevent excessive error logging in case there is a problem
            return -1;
        }
        try {
            Long threadAllocatedBytes = (Long) Reflections.invoke(getThreadAllocatedBytesMethod,
                    ManagementFactory.getThreadMXBean(), threadId);
            if (threadAllocatedBytes == null) {
                logger.error("method unexpectedly returned null:"
                        + " com.sun.management.ThreadMXBean.getThreadAllocatedBytes()");
                disabledDueToError = true;
                return -1;
            }
            return threadAllocatedBytes;
        } catch (Exception e) {
            logger.error(e.getMessage(), e);
            disabledDueToError = true;
            return -1;
        }
    }
}