Improve code by adding some null checks

src/main/java/io/lettuce/core/protocol/CommandHandler.java

@@ -82,9 +82,9 @@
 public class CommandHandler extends ChannelDuplexHandler implements HasQueuedCommands {
 
     /**
-     * When we encounter an unexpected IOException we look for these {@link Throwable#getMessage() messages} (because we have no
-     * better way to distinguish) and log them at DEBUG rather than WARN, since they are generally caused by unclean client
-     * disconnects rather than an actual problem.
+     * When we encounter an unexpected {@link IOException} we look for these {@link Throwable#getMessage() messages} (because we
+     * have no better way to distinguish) and log them at DEBUG rather than WARN, since they are generally caused by unclean
+     * client disconnects rather than an actual problem.
      */
     static final Set<String> SUPPRESS_IO_EXCEPTION_MESSAGES = LettuceSets.unmodifiableSet("Connection reset by peer",
             "Broken pipe", "Connection timed out");
@@ -123,7 +123,7 @@ public class CommandHandler extends ChannelDuplexHandler implements HasQueuedCom
 
     private Channel channel;
 
-    private ByteBuf buffer;
+    private ByteBuf readBuffer;
 
     private boolean hasDecodeProgress;
 
@@ -182,8 +182,8 @@ protected void setState(LifecycleState lifecycleState) {
         }
     }
 
-    void setBuffer(ByteBuf buffer) {
-        this.buffer = buffer;
+    void setReadBuffer(ByteBuf readBuffer) {
+        this.readBuffer = readBuffer;
     }
 
     @Override
@@ -222,7 +222,7 @@ public void channelRegistered(ChannelHandlerContext ctx) throws Exception {
 
         setState(LifecycleState.REGISTERED);
 
-        buffer = ctx.alloc().buffer(8192 * 8);
+        readBuffer = ctx.alloc().buffer(8192 * 8);
         rsm = new RedisStateMachine();
         ctx.fireChannelRegistered();
     }
@@ -242,10 +242,15 @@ public void channelUnregistered(ChannelHandlerContext ctx) throws Exception {
             ctx.fireChannelUnregistered();
             return;
         }
-
         channel = null;
-        buffer.release();
-        rsm.close();
+
+        if (readBuffer != null) {
+            readBuffer.release();
+        }
+
+        if (rsm != null) {
+            rsm.close();
+        }
         rsm = null;
 
         reset();
@@ -596,7 +601,7 @@ public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception
         }
 
         try {
-            if (buffer.refCnt() < 1) {
+            if (readBuffer == null || readBuffer.refCnt() < 1) {
                 logger.warn("{} Ignoring received data for closed or abandoned connection", logPrefix());
                 return;
             }
@@ -610,10 +615,10 @@ public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception
                 logger.trace("{} Buffer: {}", logPrefix(), input.toString(Charset.defaultCharset()).trim());
             }
 
-            buffer.touch("CommandHandler.read(…)");
-            buffer.writeBytes(input);
+            readBuffer.touch("CommandHandler.read(…)");
+            readBuffer.writeBytes(input);
 
-            decode(ctx, buffer);
+            decode(ctx, readBuffer);
         } finally {
             input.release();
         }
@@ -829,7 +834,7 @@ private boolean decode0(ChannelHandlerContext ctx, ByteBuf buffer, RedisCommand<
 
     private boolean decode0(ChannelHandlerContext ctx, ByteBuf buffer, CommandOutput<?, ?, ?> pushOutput) {
 
-        if (!rsm.decode(buffer, pushOutput, ctx::fireExceptionCaught)) {
+        if (rsm != null && !rsm.decode(buffer, pushOutput, ctx::fireExceptionCaught)) {
             return false;
         }
 
@@ -852,11 +857,11 @@ private boolean decode0(ChannelHandlerContext ctx, ByteBuf buffer, CommandOutput
     }
 
     protected boolean decode(ByteBuf buffer, CommandOutput<?, ?, ?> output) {
-        return rsm.decode(buffer, output);
+        return rsm != null && rsm.decode(buffer, output);
     }
 
     protected boolean decode(ByteBuf buffer, RedisCommand<?, ?, ?> command, CommandOutput<?, ?, ?> output) {
-        return rsm.decode(buffer, output, command::completeExceptionally);
+        return rsm != null && rsm.decode(buffer, output, command::completeExceptionally);
     }
 
     /**
@@ -918,7 +923,7 @@ private void onProtectedMode(String message) {
      * @param command
      */
     protected void afterDecode(ChannelHandlerContext ctx, RedisCommand<?, ?, ?> command) {
-        decodeBufferPolicy.afterCommandDecoded(buffer);
+        decodeBufferPolicy.afterCommandDecoded(readBuffer);
     }
 
     private void recordLatency(WithLatency withLatency, RedisCommand<?, ?, ?> command) {
@@ -960,8 +965,8 @@ private void resetInternals() {
             rsm.reset();
         }
 
-        if (buffer.refCnt() > 0) {
-            buffer.clear();
+        if (readBuffer != null && readBuffer.refCnt() > 0) {
+            readBuffer.clear();
         }
     }
 

src/main/java/io/lettuce/core/protocol/DecodeBufferPolicies.java

@@ -69,7 +69,7 @@ public static DecodeBufferPolicy ratio(float bufferUsageRatio) {
 
     /**
      * {@link DecodeBufferPolicy} that {@link ByteBuf#discardReadBytes() discards read bytes} after each decoding phase. This
-     * strategy hast the most memory efficiency but also leads to more CPU pressure.
+     * strategy has the most memory efficiency but also leads to more CPU pressure.
      *
      * @return the strategy object.
      */
@@ -80,7 +80,7 @@ public static DecodeBufferPolicy always() {
     /**
      * {@link DecodeBufferPolicy} that {@link ByteBuf#discardSomeReadBytes() discards some read bytes} after each decoding
      * phase. This strategy might discard some, all, or none of read bytes depending on its internal implementation to reduce
-     * overall memory bandwidth consumption at the cost of potentially additional memory consumption.
+     * overall CPU bandwidth consumption at the cost of potentially additional memory consumption.
      *
      * @return the strategy object.
      */

src/test/java/io/lettuce/core/protocol/CommandHandlerUnitTests.java

@@ -530,7 +530,7 @@ void shouldNotDiscardReadBytes() throws Exception {
 
         // set the command handler buffer capacity to 30, make it easy to test
         ByteBuf internalBuffer = context.alloc().buffer(30);
-        sut.setBuffer(internalBuffer);
+        sut.setReadBuffer(internalBuffer);
 
         // mock a multi reply, which will reach the buffer usage ratio
         ByteBuf msg = context.alloc().buffer(100);
@@ -559,7 +559,7 @@ void shouldDiscardReadBytes() throws Exception {
 
         // set the command handler buffer capacity to 30, make it easy to test
         ByteBuf internalBuffer = context.alloc().buffer(30);
-        sut.setBuffer(internalBuffer);
+        sut.setReadBuffer(internalBuffer);
 
         // mock a multi reply, which will reach the buffer usage ratio
         ByteBuf msg = context.alloc().buffer(100);
@@ -638,4 +638,16 @@ void shouldHandleIncompleteResponses() throws Exception {
         assertThat(hmgetCommand.get()).hasSize(3);
     }
 
+    /**
+     * @see <a href="https://github.com/redis/lettuce/issues/3087">Issue 3087</a>
+     */
+    @Test
+    void shouldHandleNullBuffers() throws Exception {
+        sut.setReadBuffer(null);
+        sut.channelRead(context, Unpooled.wrappedBuffer(("*4\r\n" + "$3\r\nONE\r\n" + "$4\r\n>TW").getBytes()));
+        assertThat(stack).hasSize(0);
+
+        sut.channelUnregistered(context);
+    }
+
 }