fix: intermitent error on multithread (#70)

async-profiler-context/src/main/java/io/pyroscope/labels/ScopedContext.java

@@ -5,19 +5,21 @@
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.function.BiConsumer;
 
 public class ScopedContext implements AutoCloseable {
-    static final ThreadLocal<Context> context = ThreadLocal.withInitial(() ->
-            new Context(0L, Collections.emptyMap())
-    );
+    static final Map<Thread, Context> threadContext = new ConcurrentHashMap<>();
 
     final Context previous;
     final Context current;
+    final Thread originalThread;
     final Ref<Map<Ref<String>, Ref<String>>> currentRef;
     boolean closed = false;
+
     public ScopedContext(LabelsSet labels) {
-        previous = context.get();
+        originalThread = Thread.currentThread();
+        previous = getContext();
         Map<Ref<String>, Ref<String>> nextContext = new HashMap<>(
                 previous.labels.size() + labels.args.length / 2
         );
@@ -58,7 +60,7 @@ public ScopedContext(LabelsSet labels) {
 
         AsyncProfiler.getInstance().setContextId(currentRef.id);
         current = new Context(currentRef.id, nextContext);
-        context.set(current);
+        setContext(current);
     }
 
 
@@ -69,7 +71,7 @@ public void close() {
         }
         closed = true;
         currentRef.refCount.decrementAndGet();
-        context.set(previous);
+        setContext(previous);
         AsyncProfiler.getInstance().setContextId(previous.id);
     }
 
@@ -79,6 +81,18 @@ public void forEach(BiConsumer<String, String> consumer) {
         }
     }
 
+    private Context getContext() {
+        return threadContext.computeIfAbsent(this.originalThread, k -> new Context(0L, Collections.emptyMap()));
+    }
+
+    private void setContext(Context context) {
+        threadContext.put(this.originalThread, context);
+    }
+
+    static Context currentContext() {
+        return threadContext.get(Thread.currentThread());
+    }
+
     static class Context {
         public final Long id;
         public final Map<Ref<String>, Ref<String>> labels;

async-profiler-context/src/test/java/io/pyroscope/labels/LabelsTest.java

@@ -68,7 +68,7 @@ void testOneLabelSet() {
                 assertEquals(1, v1.refCount.get());
             }
         }
-        assertEquals(0, ScopedContext.context.get().id);
+        assertEquals(0, ScopedContext.currentContext().id);
         assertEquals(0, ctxRef.refCount.get());
         assertEquals(1, k1.refCount.get());
         assertEquals(1, v1.refCount.get());
@@ -195,7 +195,7 @@ void testLabelsSetMerge() {
 
         }
         Pyroscope.LabelsWrapper.dump();
-        assertEquals(0, ScopedContext.context.get().id);
+        assertEquals(0, ScopedContext.currentContext().id);
         assertEquals(0, RefCounted.strings.valueToRef.size());
         assertEquals(0, RefCounted.contexts.valueToRef.size());
     }
@@ -226,7 +226,7 @@ void stressTest() throws InterruptedException {
         e.shutdown();
         e.awaitTermination(100, TimeUnit.SECONDS);
         Snapshot res = Pyroscope.LabelsWrapper.dump();
-        assertEquals(0, ScopedContext.context.get().id);
+        assertEquals(0, ScopedContext.currentContext().id);
         assertEquals(0, RefCounted.strings.valueToRef.size());
         assertEquals(0, RefCounted.contexts.valueToRef.size());
     }

async-profiler-context/src/test/java/io/pyroscope/labels/ScopedContextTest.java

@@ -0,0 +1,28 @@
+package io.pyroscope.labels;
+
+import io.pyroscope.labels.io.pyroscope.PyroscopeAsyncProfiler;
+import org.junit.jupiter.api.Test;
+
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+public class ScopedContextTest {
+
+    static {
+        PyroscopeAsyncProfiler.getAsyncProfiler();
+    }
+
+
+    /**
+     * This test demonstrates the issue reported <a href="https://github.com/grafana/pyroscope-java/issues/70">here</a>
+     */
+    @Test
+    void closeContextOnOtherThread() throws ExecutionException, InterruptedException {
+        ExecutorService executorService = Executors.newFixedThreadPool(1);
+        ScopedContext context = new ScopedContext(new LabelsSet("k1", "v1"));
+        executorService.submit(context::close).get();
+        Pyroscope.LabelsWrapper.dump();
+        new ScopedContext(new LabelsSet("k1", "v1"));
+    }
+}