Clear channel attributes on channel unregister to avoid project leaks (IDEA-158108)

java/compiler/impl/src/com/intellij/compiler/server/BuildMessageDispatcher.java

@@ -71,7 +71,14 @@ class BuildMessageDispatcher extends SimpleChannelInboundHandlerAdapter<CmdlineR
   public BuilderMessageHandler unregisterBuildMessageHandler(UUID sessionId) {
     myCanceledSessions.remove(sessionId);
     final SessionData data = mySessionDescriptors.remove(sessionId);
-    return data != null? data.handler : null;
+    if (data == null) {
+      return null;
+    }
+    final Channel channel = data.channel;
+    if (channel != null) {
+      channel.attr(SESSION_DATA).remove(); // cleanup the attribute so that session data is not leaked
+    }
+    return data.handler;
   }
 
   public void cancelSession(UUID sessionId) {

jps/jps-builders/src/org/jetbrains/jps/javac/ExternalJavacManager.java

@@ -326,7 +326,7 @@ public class ExternalJavacManager {
   private class CompilationRequestsHandler extends SimpleChannelInboundHandler<JavacRemoteProto.Message> {
     @Override
     public void channelUnregistered(ChannelHandlerContext ctx) throws Exception {
-      JavacProcessDescriptor descriptor = ctx.channel().attr(SESSION_DESCRIPTOR).get();
+      JavacProcessDescriptor descriptor = ctx.channel().attr(SESSION_DESCRIPTOR).getAndRemove();
       if (descriptor != null) {
         descriptor.setDone();
       }