remove any Reentrant locks in favor of a CAS linked list

.github/workflows/master.yml

@@ -28,6 +28,6 @@ jobs:
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@v5
       - name: build test and publish
-        run: ./gradlew assemble && ./gradlew check --info && ./gradlew publishToSonatype closeAndReleaseSonatypeStagingRepository -x check --info --stacktrace
+        run: ./gradlew assemble && ./gradlew check --info && && ./gradlew jcstress && ./gradlew publishToSonatype closeAndReleaseSonatypeStagingRepository -x check --info --stacktrace
         env:
           CI: true

.github/workflows/pull_request.yml

@@ -26,6 +26,6 @@ jobs:
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@v5
       - name: build and test
-        run: ./gradlew assemble && ./gradlew check --info --stacktrace
+        run: ./gradlew assemble && ./gradlew check --info --stacktrace && ./gradlew jcstress
         env:
           CI: true

build.gradle

@@ -1,6 +1,7 @@
+import net.ltgt.gradle.errorprone.CheckSeverity
 import org.jetbrains.kotlin.gradle.dsl.JvmTarget
 import org.jetbrains.kotlin.gradle.dsl.KotlinVersion
-import net.ltgt.gradle.errorprone.CheckSeverity
+
 import java.text.SimpleDateFormat
 
 plugins {
@@ -15,6 +16,7 @@ plugins {
     id 'com.github.ben-manes.versions' version '0.53.0'
     id "me.champeau.jmh" version "0.7.3"
     id "net.ltgt.errorprone" version '4.3.0'
+    id "io.github.reyerizo.gradle.jcstress" version "0.8.15"
 
     // Kotlin just for tests - not production code
     id 'org.jetbrains.kotlin.jvm' version '2.2.20'
@@ -229,7 +231,8 @@ nexusPublishing {
             // https://central.sonatype.org/publish/publish-portal-ossrh-staging-api/#configuration
             nexusUrl.set(uri("https://ossrh-staging-api.central.sonatype.com/service/local/"))
             // GraphQL Java does not publish snapshots, but adding this URL for completeness
-            snapshotRepositoryUrl.set(uri("https://central.sonatype.com/repository/maven-snapshots/"))        }
+            snapshotRepositoryUrl.set(uri("https://central.sonatype.com/repository/maven-snapshots/"))
+        }
     }
 }
 
@@ -258,3 +261,7 @@ tasks.named("dependencyUpdates").configure {
         isNonStable(it.candidate.version)
     }
 }
+
+jcstress {
+//    verbose = true
+}

src/jcstress/java/org/dataloader/DataLoader_Batching_Caching_JCStress.java

@@ -0,0 +1,108 @@
+package org.dataloader;
+
+import org.openjdk.jcstress.annotations.Actor;
+import org.openjdk.jcstress.annotations.Arbiter;
+import org.openjdk.jcstress.annotations.JCStressTest;
+import org.openjdk.jcstress.annotations.Outcome;
+import org.openjdk.jcstress.annotations.State;
+import org.openjdk.jcstress.infra.results.II_Result;
+
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static org.openjdk.jcstress.annotations.Expect.ACCEPTABLE;
+
+@JCStressTest
+@State
+@Outcome(id = "2000, 2000", expect = ACCEPTABLE, desc = "accepted")
+public class DataLoader_Batching_Caching_JCStress {
+
+
+    AtomicInteger counter = new AtomicInteger();
+    AtomicInteger batchLoaderCount = new AtomicInteger();
+    volatile boolean finished1;
+    volatile boolean finished2;
+
+
+    BatchLoader<String, String> batchLoader = keys -> {
+        return CompletableFuture.supplyAsync(() -> {
+            batchLoaderCount.getAndAdd(keys.size());
+            return keys;
+        });
+    };
+    DataLoader<String, String> dataLoader = DataLoaderFactory.newDataLoader(batchLoader);
+
+    public DataLoader_Batching_Caching_JCStress() {
+
+    }
+
+    @Actor
+    public void load1() {
+        for (int i = 0; i < 1000; i++) {
+            dataLoader.load("load-1-" + i);
+        }
+        // we load the same keys again
+        for (int i = 0; i < 1000; i++) {
+            dataLoader.load("load-1-" + i);
+        }
+        finished1 = true;
+    }
+
+    @Actor
+    public void load2() {
+        for (int i = 0; i < 1000; i++) {
+            dataLoader.load("load-2-" + i);
+        }
+        // we load the same keys again
+        for (int i = 0; i < 1000; i++) {
+            dataLoader.load("load-2-" + i);
+        }
+        finished2 = true;
+    }
+
+
+    @Actor
+    public void dispatch1() {
+        while (!finished1 || !finished2) {
+            try {
+                List<String> dispatchedResult = dataLoader.dispatch().get();
+                counter.getAndAdd(dispatchedResult.size());
+            } catch (Exception e) {
+                throw new RuntimeException(e);
+            }
+        }
+        try {
+            List<String> dispatchedResult = dataLoader.dispatch().get();
+            counter.getAndAdd(dispatchedResult.size());
+        } catch (Exception e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    @Actor
+    public void dispatch2() {
+        while (!finished1 || !finished2) {
+            try {
+                List<String> dispatchedResult = dataLoader.dispatch().get();
+                counter.getAndAdd(dispatchedResult.size());
+            } catch (Exception e) {
+                throw new RuntimeException(e);
+            }
+        }
+        try {
+            List<String> dispatchedResult = dataLoader.dispatch().get();
+            counter.getAndAdd(dispatchedResult.size());
+        } catch (Exception e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    @Arbiter
+    public void arbiter(II_Result r) {
+        r.r1 = counter.get();
+        r.r2 = batchLoaderCount.get();
+    }
+
+
+}

src/jcstress/java/org/dataloader/DataLoader_NoBatching_Caching_JCStress.java

@@ -0,0 +1,54 @@
+package org.dataloader;
+
+import org.openjdk.jcstress.annotations.Actor;
+import org.openjdk.jcstress.annotations.Arbiter;
+import org.openjdk.jcstress.annotations.JCStressTest;
+import org.openjdk.jcstress.annotations.Outcome;
+import org.openjdk.jcstress.annotations.State;
+import org.openjdk.jcstress.infra.results.II_Result;
+
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static org.openjdk.jcstress.annotations.Expect.ACCEPTABLE;
+import static org.openjdk.jcstress.annotations.Expect.ACCEPTABLE_INTERESTING;
+
+@JCStressTest
+@State
+@Outcome(id = "1000, 1000", expect = ACCEPTABLE, desc = "No keys loaded twice")
+@Outcome(id = "1.*, 1000", expect = ACCEPTABLE_INTERESTING, desc = "Some keys loaded twice")
+public class DataLoader_NoBatching_Caching_JCStress {
+
+
+    AtomicInteger batchLoaderCount = new AtomicInteger();
+
+    BatchLoader<String, String> batchLoader = keys -> {
+        batchLoaderCount.getAndAdd(keys.size());
+        return CompletableFuture.completedFuture(keys);
+    };
+
+
+    DataLoader<String, String> dataLoader = DataLoaderFactory.newDataLoader(batchLoader, DataLoaderOptions.newOptions().setBatchingEnabled(false).build());
+
+    @Actor
+    public void load1() {
+        for (int i = 0; i < 1000; i++) {
+            dataLoader.load("load-1-" + i);
+        }
+    }
+
+    @Actor
+    public void load2() {
+        for (int i = 0; i < 1000; i++) {
+            dataLoader.load("load-1-" + i);
+        }
+    }
+
+
+    @Arbiter
+    public void arbiter(II_Result r) {
+        r.r1 = batchLoaderCount.get();
+        r.r2 = dataLoader.getCacheMap().size();
+    }
+
+}

src/jmh/java/performance/DataLoaderDispatchPerformance.java

@@ -12,6 +12,7 @@
 import org.openjdk.jmh.annotations.Scope;
 import org.openjdk.jmh.annotations.Setup;
 import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Threads;
 import org.openjdk.jmh.annotations.Warmup;
 import org.openjdk.jmh.infra.Blackhole;
 
@@ -280,15 +281,20 @@ public void setup() {
 
         }
 
+        DataLoader ownerDL = DataLoaderFactory.newDataLoader(ownerBatchLoader);
+        DataLoader petDL = DataLoaderFactory.newDataLoader(petBatchLoader);
+
+
     }
 
 
     @Benchmark
     @BenchmarkMode(Mode.AverageTime)
     @OutputTimeUnit(TimeUnit.NANOSECONDS)
+    @Threads(Threads.MAX)
     public void loadAndDispatch(MyState myState, Blackhole blackhole) {
-        DataLoader ownerDL = DataLoaderFactory.newDataLoader(ownerBatchLoader);
-        DataLoader petDL = DataLoaderFactory.newDataLoader(petBatchLoader);
+        DataLoader ownerDL = myState.ownerDL;
+        DataLoader petDL = myState.petDL;
 
         for (Owner owner : owners.values()) {
             ownerDL.load(owner.id);

src/main/java/org/dataloader/CacheMap.java

@@ -74,10 +74,11 @@ static <K, V> CacheMap<K, V> simpleMap() {
      *
      * @return the cached value, or {@code null} if not found (depends on cache implementation)
      */
-    @Nullable  CompletableFuture<V> get(K key);
+    @Nullable CompletableFuture<V> get(K key);
 
     /**
      * Gets a collection of CompletableFutures from the cache map.
+     *
      * @return the collection of cached values
      */
     Collection<CompletableFuture<V>> getAll();
@@ -90,7 +91,7 @@ static <K, V> CacheMap<K, V> simpleMap() {
      *
      * @return the cache map for fluent coding
      */
-    CacheMap<K, V> set(K key, CompletableFuture<V> value);
+    CompletableFuture<V> setIfAbsent(K key, CompletableFuture<V> value);
 
     /**
      * Deletes the entry with the specified key from the cache map, if it exists.
@@ -107,4 +108,13 @@ static <K, V> CacheMap<K, V> simpleMap() {
      * @return the cache map for fluent coding
      */
     CacheMap<K, V> clear();
+
+    /**
+     * Returns the current size of the cache. This is not used by DataLoader directly
+     * and intended for testing and debugging.
+     * If a cache doesn't support it, it can throw an Exception.
+     *
+     * @return
+     */
+    int size();
 }