Issue ReactiveX#12 AtomicRateLimiter tests and additional documentation

Author: storozhukBM

build.gradle

@@ -69,6 +69,9 @@ dependencies {
     testCompile "ch.qos.logback:logback-classic:0.9.26"
     testCompile "io.dropwizard.metrics:metrics-healthchecks:3.1.2"
     testCompile "org.mockito:mockito-core:1.10.19"
+    testCompile "org.powermock:powermock:1.6.6"
+    testCompile "org.powermock:powermock-api-mockito:1.6.6"
+    testCompile "org.powermock:powermock-module-junit4:1.6.6"
     testCompile "io.projectreactor:reactor-core:2.5.0.M2"
     testCompile "com.jayway.awaitility:awaitility:1.7.0"
 

src/jmh/java/javaslang/circuitbreaker/30-Nov-2016-i7-I7-5557U-OSX-Java-1.8.0_112-x64.txt

@@ -4,7 +4,6 @@
 import javaslang.ratelimiter.RateLimiterConfig;
 import javaslang.ratelimiter.internal.AtomicRateLimiter;
 import javaslang.ratelimiter.internal.SemaphoreBasedRateLimiter;
-import javaslang.ratelimiter.internal.TimeBasedRateLimiter;
 import org.openjdk.jmh.annotations.Benchmark;
 import org.openjdk.jmh.annotations.BenchmarkMode;
 import org.openjdk.jmh.annotations.Fork;
@@ -33,11 +32,9 @@ public class RateLimiterBenchmark {
     private static final int THREAD_COUNT = 2;
 
     private RateLimiter semaphoreBasedRateLimiter;
-    private RateLimiter timeBasedRateLimiter;
     private RateLimiter atomicRateLimiter;
 
     private Supplier<String> semaphoreGuardedSupplier;
-    private Supplier<String> timeGuardedSupplier;
     private Supplier<String> atomicGuardedSupplier;
 
     @Setup
@@ -48,15 +45,13 @@ public void setUp() {
             .timeoutDuration(Duration.ofSeconds(5))
             .build();
         semaphoreBasedRateLimiter = new SemaphoreBasedRateLimiter("semaphoreBased", rateLimiterConfig);
-        timeBasedRateLimiter = new TimeBasedRateLimiter("timeBased", rateLimiterConfig);
         atomicRateLimiter = new AtomicRateLimiter("atomicBased", rateLimiterConfig);
 
         Supplier<String> stringSupplier = () -> {
             Blackhole.consumeCPU(1);
             return "Hello Benchmark";
         };
         semaphoreGuardedSupplier = RateLimiter.decorateSupplier(semaphoreBasedRateLimiter, stringSupplier);
-        timeGuardedSupplier = RateLimiter.decorateSupplier(timeBasedRateLimiter, stringSupplier);
         atomicGuardedSupplier = RateLimiter.decorateSupplier(atomicRateLimiter, stringSupplier);
     }
 
@@ -69,15 +64,6 @@ public String semaphoreBasedPermission() {
         return semaphoreGuardedSupplier.get();
     }
 
-    @Benchmark
-    @Threads(value = THREAD_COUNT)
-    @Warmup(iterations = WARMUP_COUNT)
-    @Fork(value = FORK_COUNT)
-    @Measurement(iterations = ITERATION_COUNT)
-    public String timeBasedPermission() {
-        return timeGuardedSupplier.get();
-    }
-
     @Benchmark
     @Threads(value = THREAD_COUNT)
     @Warmup(iterations = WARMUP_COUNT)

src/jmh/java/javaslang/circuitbreaker/RateLimiterBenchmark.java

@@ -7,8 +7,7 @@
 public class RateLimiterConfig {
     private static final String TIMEOUT_DURATION_MUST_NOT_BE_NULL = "TimeoutDuration must not be null";
     private static final String LIMIT_REFRESH_PERIOD_MUST_NOT_BE_NULL = "LimitRefreshPeriod must not be null";
-
-    private static final Duration ACCEPTABLE_REFRESH_PERIOD = Duration.ofNanos(1L); // TODO: use jmh to find real one
+    private static final Duration ACCEPTABLE_REFRESH_PERIOD = Duration.ofNanos(1L);
 
     private final Duration timeoutDuration;
     private final Duration limitRefreshPeriod;

src/main/java/javaslang/ratelimiter/RateLimiterConfig.java

@@ -42,9 +42,7 @@ public AtomicRateLimiter(String name, RateLimiterConfig rateLimiterConfig) {
         permissionsPerCycle = rateLimiterConfig.getLimitForPeriod();
 
         waitingThreads = new AtomicInteger(0);
-        long activeCycle = nanoTime() / cyclePeriodInNanos;
-        int activePermissions = permissionsPerCycle;
-        state = new AtomicReference<>(new State(activeCycle, activePermissions, 0));
+        state = new AtomicReference<>(new State(0, 0, 0));
     }
 
     /**
@@ -69,7 +67,7 @@ public boolean getPermission(final Duration timeoutDuration) {
      * @return next {@link State}
      */
     private State calculateNextState(final long timeoutInNanos, final State activeState) {
-        long currentNanos = nanoTime();
+        long currentNanos = currentNanoTime();
         long currentCycle = currentNanos / cyclePeriodInNanos;
 
         long nextCycle = activeState.activeCycle;
@@ -85,6 +83,7 @@ private State calculateNextState(final long timeoutInNanos, final State activeSt
         return nextState;
     }
 
+
     /**
      * Calculates time to wait for next permission as
      * [time to the next cycle] + [duration of full cycles until reserved permissions expire]
@@ -147,19 +146,27 @@ private boolean waitForPermissionIfNecessary(final long timeoutInNanos, final lo
 
     /**
      * Parks {@link Thread} for nanosToWait.
+     * <p>If the current thread is {@linkplain Thread#interrupted}
+     * while waiting for a permit then it won't throw {@linkplain InterruptedException},
+     * but its interrupt status will be set.
      *
      * @param nanosToWait nanoseconds caller need to wait
      * @return true if caller was not {@link Thread#interrupted} while waiting
      */
     private boolean waitForPermission(final long nanosToWait) {
         waitingThreads.incrementAndGet();
-        long deadline = nanoTime() + nanosToWait;
-        while (nanoTime() < deadline || currentThread().isInterrupted()) {
-            long sleepBlockDuration = deadline - nanoTime();
+        long deadline = currentNanoTime() + nanosToWait;
+        boolean wasInterrupted = false;
+        while (currentNanoTime() < deadline && !wasInterrupted) {
+            long sleepBlockDuration = deadline - currentNanoTime();
             parkNanos(sleepBlockDuration);
+            wasInterrupted = Thread.interrupted();
         }
         waitingThreads.decrementAndGet();
-        return !currentThread().isInterrupted();
+        if (wasInterrupted) {
+            currentThread().interrupt();
+        }
+        return !wasInterrupted;
     }
 
     /**
@@ -182,7 +189,7 @@ public RateLimiterConfig getRateLimiterConfig() {
      * {@inheritDoc}
      */
     @Override
-    public Metrics getMetrics() {
+    public AtomicRateLimiterMetrics getMetrics() {
         return new AtomicRateLimiterMetrics();
     }
 
@@ -201,6 +208,7 @@ public Metrics getMetrics() {
      * </ul>
      */
     private static class State {
+
         private final long activeCycle;
         private final int activePermissions;
         private final long nanosToWait;
@@ -210,12 +218,14 @@ public State(final long activeCycle, final int activePermissions, final long nan
             this.activePermissions = activePermissions;
             this.nanosToWait = nanosToWait;
         }
+
     }
 
     /**
      * Enhanced {@link Metrics} with some implementation specific details
      */
     public final class AtomicRateLimiterMetrics implements Metrics {
+
         private AtomicRateLimiterMetrics() {
         }
 
@@ -228,5 +238,33 @@ private AtomicRateLimiterMetrics() {
         public int getNumberOfWaitingThreads() {
             return waitingThreads.get();
         }
+
+        /**
+         * @return estimated time duration in nanos to wait for the next permission
+         */
+        public long getNanosToWait() {
+            State currentState = state.get();
+            State estimatedState = calculateNextState(-1, currentState);
+            return estimatedState.nanosToWait;
+        }
+
+        /**
+         * Estimates count of permissions available permissions.
+         * Can be negative if some permissions where reserved.
+         *
+         * @return estimated count of permissions
+         */
+        public long getAvailablePermissions() {
+            State currentState = state.get();
+            State estimatedState = calculateNextState(-1, currentState);
+            return estimatedState.activePermissions;
+        }
+    }
+
+    /**
+     * Created only for test purposes. Simply calls {@link System#nanoTime()}
+     */
+    private long currentNanoTime() {
+        return nanoTime();
     }
 }