remove java.util.concurrent.ThreadLocalRandom to keep compatible with…

… jdk6. alibaba#28
qipa · Sep 19, 2018 · 3221e44 · 3221e44
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diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
@@ -13,6 +13,7 @@
 
 ## 开发者相关
 
+编绎要求jdk7以上。因为使用到了jdk7才有的`java.lang.management.BufferPoolMXBea`，运行时要求是jdk6。
 
 ### 安装到本地
 

diff --git a/core/src/main/java/com/taobao/arthas/core/util/ThreadLocalRandom.java b/core/src/main/java/com/taobao/arthas/core/util/ThreadLocalRandom.java
@@ -0,0 +1,271 @@
+package com.taobao.arthas.core.util;
+import java.security.SecureRandom;
+import java.util.Random;
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicLong;
+
+/**
+ * A random number generator isolated to the current thread. Like the global {@link java.util.Random} generator used by
+ * the {@link java.lang.Math} class, a {@code ThreadLocalRandom} is initialized with an internally generated seed that
+ * may not otherwise be modified. When applicable, use of {@code ThreadLocalRandom} rather than shared {@code Random}
+ * objects in concurrent programs will typically encounter much less overhead and contention. Use of
+ * {@code ThreadLocalRandom} is particularly appropriate when multiple tasks (for example, each a
+ * {@link io.netty.util.internal.chmv8.ForkJoinTask}) use random numbers in parallel in thread pools.
+ *
+ * <p>
+ * Usages of this class should typically be of the form: {@code ThreadLocalRandom.current().nextX(...)} (where {@code X}
+ * is {@code Int}, {@code Long}, etc). When all usages are of this form, it is never possible to accidently share a
+ * {@code ThreadLocalRandom} across multiple threads.
+ *
+ * <p>
+ * This class also provides additional commonly used bounded random generation methods.
+ *
+ * //since 1.7 //author Doug Lea
+ */
+@SuppressWarnings("all")
+public class ThreadLocalRandom extends Random {
+    private static final AtomicLong seedUniquifier = new AtomicLong();
+
+    private static volatile long initialSeedUniquifier;
+
+    public static void setInitialSeedUniquifier(long initialSeedUniquifier) {
+        ThreadLocalRandom.initialSeedUniquifier = initialSeedUniquifier;
+    }
+
+    public static synchronized long getInitialSeedUniquifier() {
+        // Use the value set via the setter.
+        long initialSeedUniquifier = ThreadLocalRandom.initialSeedUniquifier;
+        // Otherwise, generate one.
+        if (initialSeedUniquifier == 0) {
+            // Try to generate a real random number from /dev/random.
+            // Get from a different thread to avoid blocking indefinitely on a machine without much entrophy.
+            final BlockingQueue<Long> queue = new LinkedBlockingQueue<Long>();
+            Thread generatorThread = new Thread("initialSeedUniquifierGenerator") {
+                @Override
+                public void run() {
+                    SecureRandom random = new SecureRandom(); // Get the real random seed from /dev/random
+                    queue.add(random.nextLong());
+                }
+            };
+            generatorThread.start();
+
+            // Get the random seed from the thread with timeout.
+            final long timeoutSeconds = 3;
+            final long deadLine = System.nanoTime() + TimeUnit.SECONDS.toNanos(timeoutSeconds);
+            for (;;) {
+                long waitTime = deadLine - System.nanoTime();
+                if (waitTime <= 0) {
+                    break;
+                }
+
+                try {
+                    Long result = queue.poll(waitTime, TimeUnit.NANOSECONDS);
+                    if (result != null) {
+                        initialSeedUniquifier = result;
+                        break;
+                    }
+                } catch (InterruptedException ignore) {
+                    // Ignore
+                }
+            }
+
+            // Just in case the initialSeedUniquifier is zero or some other constant
+            initialSeedUniquifier ^= 0x3255ecdc33bae119L; // just a meaningless random number
+            initialSeedUniquifier ^= Long.reverse(System.nanoTime());
+
+            ThreadLocalRandom.initialSeedUniquifier = initialSeedUniquifier;
+        }
+
+        return initialSeedUniquifier;
+    }
+
+    private static long newSeed() {
+        for (;;) {
+            final long current = seedUniquifier.get();
+            final long actualCurrent = current != 0 ? current : getInitialSeedUniquifier();
+
+            // L'Ecuyer, "Tables of Linear Congruential Generators of Different Sizes and Good Lattice Structure", 1999
+            final long next = actualCurrent * 181783497276652981L;
+
+            if (seedUniquifier.compareAndSet(current, next)) {
+                return next ^ System.nanoTime();
+            }
+        }
+    }
+
+    // same constants as Random, but must be redeclared because private
+    private static final long multiplier = 0x5DEECE66DL;
+    private static final long addend = 0xBL;
+    private static final long mask = (1L << 48) - 1;
+
+    /**
+     * The random seed. We can't use super.seed.
+     */
+    private long rnd;
+
+    /**
+     * Initialization flag to permit calls to setSeed to succeed only while executing the Random constructor. We can't
+     * allow others since it would cause setting seed in one part of a program to unintentionally impact other usages by
+     * the thread.
+     */
+    boolean initialized;
+
+    // Padding to help avoid memory contention among seed updates in
+    // different TLRs in the common case that they are located near
+    // each other.
+    private long pad0, pad1, pad2, pad3, pad4, pad5, pad6, pad7;
+
+    /**
+     * Constructor called only by localRandom.initialValue.
+     */
+    ThreadLocalRandom() {
+        super(newSeed());
+        initialized = true;
+    }
+
+    /**
+     * The actual ThreadLocal
+     */
+    private static final ThreadLocal<ThreadLocalRandom> localRandom = new ThreadLocal<ThreadLocalRandom>() {
+        protected ThreadLocalRandom initialValue() {
+            return new ThreadLocalRandom();
+        }
+    };
+
+    /**
+     * Returns the current thread's {@code ThreadLocalRandom}.
+     *
+     * @return the current thread's {@code ThreadLocalRandom}
+     */
+    public static ThreadLocalRandom current() {
+        return localRandom.get();
+    }
+
+    /**
+     * Throws {@code UnsupportedOperationException}. Setting seeds in this generator is not supported.
+     *
+     * @throws UnsupportedOperationException
+     *             always
+     */
+    public void setSeed(long seed) {
+        if (initialized) {
+            throw new UnsupportedOperationException();
+        }
+        rnd = (seed ^ multiplier) & mask;
+    }
+
+    protected int next(int bits) {
+        rnd = (rnd * multiplier + addend) & mask;
+        return (int) (rnd >>> (48 - bits));
+    }
+
+    /**
+     * Returns a pseudorandom, uniformly distributed value between the given least value (inclusive) and bound
+     * (exclusive).
+     *
+     * @param least
+     *            the least value returned
+     * @param bound
+     *            the upper bound (exclusive)
+     * @throws IllegalArgumentException
+     *             if least greater than or equal to bound
+     * @return the next value
+     */
+    public int nextInt(int least, int bound) {
+        if (least >= bound) {
+            throw new IllegalArgumentException();
+        }
+        return nextInt(bound - least) + least;
+    }
+
+    /**
+     * Returns a pseudorandom, uniformly distributed value between 0 (inclusive) and the specified value (exclusive).
+     *
+     * @param n
+     *            the bound on the random number to be returned. Must be positive.
+     * @return the next value
+     * @throws IllegalArgumentException
+     *             if n is not positive
+     */
+    public long nextLong(long n) {
+        if (n <= 0) {
+            throw new IllegalArgumentException("n must be positive");
+        }
+
+        // Divide n by two until small enough for nextInt. On each
+        // iteration (at most 31 of them but usually much less),
+        // randomly choose both whether to include high bit in result
+        // (offset) and whether to continue with the lower vs upper
+        // half (which makes a difference only if odd).
+        long offset = 0;
+        while (n >= Integer.MAX_VALUE) {
+            int bits = next(2);
+            long half = n >>> 1;
+            long nextn = ((bits & 2) == 0) ? half : n - half;
+            if ((bits & 1) == 0) {
+                offset += n - nextn;
+            }
+            n = nextn;
+        }
+        return offset + nextInt((int) n);
+    }
+
+    /**
+     * Returns a pseudorandom, uniformly distributed value between the given least value (inclusive) and bound
+     * (exclusive).
+     *
+     * @param least
+     *            the least value returned
+     * @param bound
+     *            the upper bound (exclusive)
+     * @return the next value
+     * @throws IllegalArgumentException
+     *             if least greater than or equal to bound
+     */
+    public long nextLong(long least, long bound) {
+        if (least >= bound) {
+            throw new IllegalArgumentException();
+        }
+        return nextLong(bound - least) + least;
+    }
+
+    /**
+     * Returns a pseudorandom, uniformly distributed {@code double} value between 0 (inclusive) and the specified value
+     * (exclusive).
+     *
+     * @param n
+     *            the bound on the random number to be returned. Must be positive.
+     * @return the next value
+     * @throws IllegalArgumentException
+     *             if n is not positive
+     */
+    public double nextDouble(double n) {
+        if (n <= 0) {
+            throw new IllegalArgumentException("n must be positive");
+        }
+        return nextDouble() * n;
+    }
+
+    /**
+     * Returns a pseudorandom, uniformly distributed value between the given least value (inclusive) and bound
+     * (exclusive).
+     *
+     * @param least
+     *            the least value returned
+     * @param bound
+     *            the upper bound (exclusive)
+     * @return the next value
+     * @throws IllegalArgumentException
+     *             if least greater than or equal to bound
+     */
+    public double nextDouble(double least, double bound) {
+        if (least >= bound) {
+            throw new IllegalArgumentException();
+        }
+        return nextDouble() * (bound - least) + least;
+    }
+
+    private static final long serialVersionUID = -5851777807851030925L;
+}
diff --git a/core/src/main/java/com/taobao/arthas/core/util/metrics/RateCounter.java b/core/src/main/java/com/taobao/arthas/core/util/metrics/RateCounter.java
@@ -1,17 +1,18 @@
 package com.taobao.arthas.core.util.metrics;
 
-import java.util.concurrent.ThreadLocalRandom;
 import java.util.concurrent.atomic.AtomicLong;
 import java.util.concurrent.atomic.AtomicLongArray;
 
+import com.taobao.arthas.core.util.ThreadLocalRandom;
+
 /**
  * <pre>
  * 统计平均速率，比如统计5秒内的平均速率。
  * 5秒的数据是：234, 345,124,366,235，
  * 则速率是 (234+345+124+366+235)/5 = 260
- * 
+ *
  * </pre>
- * 
+ *
  * @author hengyunabc 2015年12月18日 下午3:40:19
  *
  */
Original file line number	Diff line number	Diff line change
Expand Up		@@ -13,6 +13,7 @@

		## 开发者相关

		编绎要求jdk7以上。因为使用到了jdk7才有的`java.lang.management.BufferPoolMXBea`，运行时要求是jdk6。

		### 安装到本地

Expand Down