Ensure session counts are reported thread safe

Author: Pezzah

bugsnag/src/main/java/com/bugsnag/Bugsnag.java

@@ -472,11 +472,16 @@ public boolean notify(Report report, Callback reportCallback) {
         Session session = sessionTracker.getSession();
 
         if (session != null) {
-            if (report.getUnhandled()) {
-                session.incrementUnhandledCount();
-            } else {
-                session.incrementHandledCount();
+            try {
+                if (report.getUnhandled()) {
+                    session = session.incrementUnhandledCountAndClone();
+                } else {
+                    session = session.incrementHandledCountAndClone();
+                }
+            } catch (InterruptedException ex) {
+                // Failed to increment session counts properly
             }
+
             report.setSession(session);
         }
 

bugsnag/src/main/java/com/bugsnag/Session.java

@@ -3,10 +3,13 @@
 import com.bugsnag.serialization.Expose;
 
 import java.util.Date;
+import java.util.concurrent.Semaphore;
 import java.util.concurrent.atomic.AtomicInteger;
 
 class Session {
 
+    private final Semaphore incrementRequest = new Semaphore(1);
+
     private final String id;
     private final Date startedAt;
     private final AtomicInteger handledCount;
@@ -19,6 +22,13 @@ class Session {
         this.unhandledCount = new AtomicInteger(0);
     }
 
+    private Session(String id, Date startedAt, int handledCount, int unhandledCount) {
+        this.id = id;
+        this.startedAt = startedAt;
+        this.handledCount = new AtomicInteger(handledCount);
+        this.unhandledCount = new AtomicInteger(unhandledCount);
+    }
+
     int getHandledCount() {
         return handledCount.get();
     }
@@ -27,6 +37,16 @@ void incrementHandledCount() {
         this.handledCount.incrementAndGet();
     }
 
+    Session incrementHandledCountAndClone() throws InterruptedException {
+        try {
+            incrementRequest.acquire();
+            incrementHandledCount();
+            return cloneSession();
+        } finally {
+            incrementRequest.release();
+        }
+    }
+
     int getUnhandledCount() {
         return unhandledCount.get();
     }
@@ -35,6 +55,20 @@ void incrementUnhandledCount() {
         this.unhandledCount.incrementAndGet();
     }
 
+    Session incrementUnhandledCountAndClone() throws InterruptedException {
+        try {
+            incrementRequest.acquire();
+            incrementUnhandledCount();
+            return cloneSession();
+        } finally {
+            incrementRequest.release();
+        }
+    }
+
+    private Session cloneSession() {
+        return new Session(id, startedAt, handledCount.get(), unhandledCount.get());
+    }
+
     String getId() {
         return id;
     }