Use a non-blocking output stream for socket writes (docker-java#1769)

derklaro · web-flow · commit e100e2581fd5 · 2022-02-04T17:13:16.000-05:00
Essentially: Channels.newOutputStream and Channels.newInputStream are synchronizing on the blocking lock provided by the SelectableChannel#blockingLock method. This prevents writing a command to a container stdin while there is no output printed to stdout. This is a long known issue in java and was fixed partially in java 13 (see https://bugs.java.com/bugdatabase/view_bug.do?bug_id=8222774). Concurrent read/writes aren't a problem there anymore as well. References: https://bugs.java.com/bugdatabase/view_bug.do?bug_id=4509080 https://bugs.java.com/bugdatabase/view_bug.do?bug_id=4774871 https://bugs.java.com/bugdatabase/view_bug.do?bug_id=6977788 Closes docker-java#1768
diff --git a/docker-java-transport/src/main/java/com/github/dockerjava/transport/UnixSocket.java b/docker-java-transport/src/main/java/com/github/dockerjava/transport/UnixSocket.java
@@ -6,8 +6,10 @@
 import java.net.Socket;
 import java.net.SocketAddress;
 import java.net.SocketException;
+import java.nio.ByteBuffer;
 import java.nio.channels.Channels;
 import java.nio.channels.SocketChannel;
+import java.nio.channels.WritableByteChannel;
 
 public class UnixSocket extends AbstractSocket {
 
@@ -67,7 +69,7 @@ public OutputStream getOutputStream() throws IOException {
             throw new SocketException("Socket output is shutdown");
         }
 
-        return Channels.newOutputStream(socketChannel);
+        return Channels.newOutputStream(new WrappedWritableByteChannel());
     }
 
     @Override
@@ -85,4 +87,22 @@ public void close() throws IOException {
         super.close();
         this.socketChannel.close();
     }
+
+    private class WrappedWritableByteChannel implements WritableByteChannel {
+
+        @Override
+        public int write(ByteBuffer src) throws IOException {
+            return UnixSocket.this.socketChannel.write(src);
+        }
+
+        @Override
+        public boolean isOpen() {
+            return UnixSocket.this.socketChannel.isOpen();
+        }
+
+        @Override
+        public void close() throws IOException {
+            UnixSocket.this.socketChannel.close();
+        }
+    }
 }
