Update shaded JCTools queue due to live-lock (fixes #127)

In #127, a live-lock occurs in the write buffer due to a race when the
consumer tries to transition to the last buffer. This is a shaded copy
of JCTools' MpscGrowableLinkedArrayQueue and fixed in 2.0 (see
JCTools/JCTools#135). This is a difficult to
reproduce bug, except for the reporter due to having thousands of
instances on a loaded system.

The shaded copy is more verbose than the previous one, but that is to
minimize the divergency and introducing bugs by cutting too deep.

Updating to Guava 20 required minor changes due to that cache now
supporting write-through entries. The adapter now mirrors the new
behavior.

Thanks to everyones patience and help in fixing the bug.

caffeine/build.gradle

@@ -41,7 +41,6 @@ dependencies {
   jmh benchmark_libraries.infinispan
   jmh benchmark_libraries.jackrabbit
   jmh benchmark_libraries.elastic_search
-  jmh benchmark_libraries.jctools_experimental
   jmh benchmark_libraries.concurrentlinkedhashmap
 
   javaPoetCompile libraries.guava

caffeine/src/javaPoet/java/com/github/benmanes/caffeine/cache/Specifications.java

@@ -99,7 +99,8 @@ public final class Specifications {
   public static final TypeName WRITE_ORDER_DEQUE = ParameterizedTypeName.get(
       ClassName.get(PACKAGE_NAME, "WriteOrderDeque"), NODE);
 
-  public static final ClassName WRITE_QUEUE_TYPE = ClassName.get(PACKAGE_NAME, "WriteBuffer");
+  public static final ClassName WRITE_QUEUE_TYPE =
+      ClassName.get(PACKAGE_NAME, "MpscGrowableArrayQueue");
   public static final TypeName WRITE_QUEUE = ParameterizedTypeName.get(
       WRITE_QUEUE_TYPE, ClassName.get(Runnable.class));
 

caffeine/src/main/java/com/github/benmanes/caffeine/base/UnsafeAccess.java

@@ -29,6 +29,7 @@
  *
  * @author [email protected] (Ben Manes)
  */
+@SuppressWarnings("restriction")
 public final class UnsafeAccess {
   static final String ANDROID = "THE_ONE";
   static final String OPEN_JDK = "theUnsafe";

caffeine/src/main/java/com/github/benmanes/caffeine/cache/BoundedLocalCache.java

@@ -235,7 +235,7 @@ protected boolean buffersWrites() {
     return false;
   }
 
-  protected WriteBuffer<Runnable> writeBuffer() {
+  protected MpscGrowableArrayQueue<Runnable> writeBuffer() {
     throw new UnsupportedOperationException();
   }
 
@@ -634,6 +634,7 @@ void evictFromMain(int candidates) {
    * @param victimKey the key for the entry chosen by the eviction policy for replacement
    * @return if the candidate should be admitted and the victim ejected
    */
+  @GuardedBy("evictionLock")
   boolean admit(K candidateKey, K victimKey) {
     int victimFreq = frequencySketch().frequency(victimKey);
     int candidateFreq = frequencySketch().frequency(candidateKey);