Track if proxy protocol messages need buffering

zuul-core/src/main/java/com/netflix/netty/common/proxyprotocol/ElbProxyProtocolChannelHandler.java

@@ -48,26 +48,40 @@ public void addProxyProtocol(ChannelPipeline pipeline) {
 
     @Override
     public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
-        if (withProxyProtocol && isHAPMDetected(msg)) {
+        if (!withProxyProtocol) {
+            ctx.pipeline().remove(this);
+            super.channelRead(ctx, msg);
+            return;
+        }
+
+        ProtocolDetectionState haProxyState = getDetectionState(msg);
+        if (haProxyState == ProtocolDetectionState.DETECTED) {
             ctx.pipeline()
                     .addAfter(NAME, null, new HAProxyMessageChannelHandler())
                     .replace(this, null, new HAProxyMessageDecoder());
         } else {
-            if (withProxyProtocol) {
-                final int port = ctx.channel()
-                        .attr(SourceAddressChannelHandler.ATTR_SERVER_LOCAL_PORT)
-                        .get();
-                // This likely means initialization was requested with proxy protocol, but we encountered a non-ppv2
-                // message
-                registry.counter("zuul.hapm.decode", "success", "false", "port", String.valueOf(port))
-                        .increment();
-            }
+            final int port = ctx.channel()
+                    .attr(SourceAddressChannelHandler.ATTR_SERVER_LOCAL_PORT)
+                    .get();
+
+            String needsMoreData = haProxyState == ProtocolDetectionState.NEEDS_MORE_DATA ? "true" : "false";
+            // This likely means initialization was requested with proxy protocol, but we encountered a non-ppv2
+            // message
+            registry.counter(
+                            "zuul.hapm.decode",
+                            "success",
+                            "false",
+                            "port",
+                            String.valueOf(port),
+                            "needs_more_data",
+                            needsMoreData)
+                    .increment();
             ctx.pipeline().remove(this);
         }
         super.channelRead(ctx, msg);
     }
 
-    private boolean isHAPMDetected(Object msg) {
-        return HAProxyMessageDecoder.detectProtocol((ByteBuf) msg).state() == ProtocolDetectionState.DETECTED;
+    private ProtocolDetectionState getDetectionState(Object msg) {
+        return HAProxyMessageDecoder.detectProtocol((ByteBuf) msg).state();
     }
 }

zuul-core/src/test/java/com/netflix/netty/common/proxyprotocol/ElbProxyProtocolChannelHandlerTest.java

@@ -151,7 +151,8 @@ void incrementCounterWhenPPEnabledButNonHAPMMessage() {
         assertEquals(dropped, buf);
         buf.release();
 
-        final Counter counter = registry.counter("zuul.hapm.decode", "success", "false", "port", String.valueOf(port));
+        final Counter counter = registry.counter(
+                "zuul.hapm.decode", "success", "false", "port", String.valueOf(port), "needs_more_data", "false");
         assertEquals(1, counter.count());
     }
 
@@ -181,6 +182,31 @@ void detectsSplitPpv1Message() {
         assertNull(channel.pipeline().context(ElbProxyProtocolChannelHandler.class));
     }
 
+    @Test
+    void tracksSplitMessage() {
+        EmbeddedChannel channel = new EmbeddedChannel();
+        // This is normally done by Server.
+        channel.attr(Server.CONN_DIMENSIONS).set(Attrs.newInstance());
+        int port = 7007;
+        channel.attr(SourceAddressChannelHandler.ATTR_SERVER_LOCAL_PORT).set(port);
+
+        channel.pipeline()
+                .addLast(ElbProxyProtocolChannelHandler.NAME, new ElbProxyProtocolChannelHandler(registry, true));
+        ByteBuf buf1 = Unpooled.wrappedBuffer("PROXY TCP4".getBytes(StandardCharsets.US_ASCII));
+        channel.writeInbound(buf1);
+
+        Object msg = channel.readInbound();
+        assertEquals(buf1, msg);
+        buf1.release();
+
+        // The handler should remove itself.
+        assertNull(channel.pipeline().context(ElbProxyProtocolChannelHandler.class));
+
+        Counter counter = registry.counter(
+                "zuul.hapm.decode", "success", "false", "port", String.valueOf(port), "needs_more_data", "true");
+        assertEquals(1, counter.count());
+    }
+
     @Test
     void negotiateProxy_ppv1_ipv4() {
         EmbeddedChannel channel = new EmbeddedChannel();