Allow only a fixed-size receive predictor (elastic#26165)

With this commit we simplify our network layer by only allowing to define a
fixed receive predictor size instead of a minimum and maximum value. This also
means that the following (previously undocumented) settings are removed:

* http.netty.receive_predictor_min
* http.netty.receive_predictor_max

Using an adaptive sizing policy in the receive predictor is a very low-level
optimization. The implications on allocation behavior are extremely hard to grasp
(see our previous work in elastic#23185) and adaptive sizing does not provide a lot of
benefits (see benchmarks in elastic#26165 for more details).

modules/transport-netty4/src/main/java/org/elasticsearch/http/netty4/Netty4HttpServerTransport.java

@@ -22,7 +22,6 @@
 import com.carrotsearch.hppc.IntHashSet;
 import com.carrotsearch.hppc.IntSet;
 import io.netty.bootstrap.ServerBootstrap;
-import io.netty.channel.AdaptiveRecvByteBufAllocator;
 import io.netty.channel.Channel;
 import io.netty.channel.ChannelFuture;
 import io.netty.channel.ChannelHandler;
@@ -88,7 +87,6 @@
 import java.util.regex.Pattern;
 
 import static org.elasticsearch.common.settings.Setting.boolSetting;
-import static org.elasticsearch.common.settings.Setting.byteSizeSetting;
 import static org.elasticsearch.common.util.concurrent.EsExecutors.daemonThreadFactory;
 import static org.elasticsearch.http.HttpTransportSettings.SETTING_CORS_ALLOW_CREDENTIALS;
 import static org.elasticsearch.http.HttpTransportSettings.SETTING_CORS_ALLOW_HEADERS;
@@ -132,10 +130,6 @@ public class Netty4HttpServerTransport extends AbstractLifecycleComponent implem
 
     public static final Setting<ByteSizeValue> SETTING_HTTP_NETTY_RECEIVE_PREDICTOR_SIZE =
         Setting.byteSizeSetting("http.netty.receive_predictor_size", new ByteSizeValue(64, ByteSizeUnit.KB), Property.NodeScope);
-    public static final Setting<ByteSizeValue> SETTING_HTTP_NETTY_RECEIVE_PREDICTOR_MIN =
-        byteSizeSetting("http.netty.receive_predictor_min", SETTING_HTTP_NETTY_RECEIVE_PREDICTOR_SIZE, Property.NodeScope);
-    public static final Setting<ByteSizeValue> SETTING_HTTP_NETTY_RECEIVE_PREDICTOR_MAX =
-        byteSizeSetting("http.netty.receive_predictor_max", SETTING_HTTP_NETTY_RECEIVE_PREDICTOR_SIZE, Property.NodeScope);
 
 
     protected final NetworkService networkService;
@@ -227,17 +221,8 @@ public Netty4HttpServerTransport(Settings settings, NetworkService networkServic
         this.tcpReceiveBufferSize = SETTING_HTTP_TCP_RECEIVE_BUFFER_SIZE.get(settings);
         this.detailedErrorsEnabled = SETTING_HTTP_DETAILED_ERRORS_ENABLED.get(settings);
 
-        // See AdaptiveReceiveBufferSizePredictor#DEFAULT_XXX for default values in netty..., we can use higher ones for us, even fixed one
-        ByteSizeValue receivePredictorMin = SETTING_HTTP_NETTY_RECEIVE_PREDICTOR_MIN.get(settings);
-        ByteSizeValue receivePredictorMax = SETTING_HTTP_NETTY_RECEIVE_PREDICTOR_MAX.get(settings);
-        if (receivePredictorMax.getBytes() == receivePredictorMin.getBytes()) {
-            recvByteBufAllocator = new FixedRecvByteBufAllocator(Math.toIntExact(receivePredictorMax.getBytes()));
-        } else {
-            recvByteBufAllocator = new AdaptiveRecvByteBufAllocator(
-                Math.toIntExact(receivePredictorMin.getBytes()),
-                Math.toIntExact(receivePredictorMin.getBytes()),
-                Math.toIntExact(receivePredictorMax.getBytes()));
-        }
+        ByteSizeValue receivePredictor = SETTING_HTTP_NETTY_RECEIVE_PREDICTOR_SIZE.get(settings);
+        recvByteBufAllocator = new FixedRecvByteBufAllocator(receivePredictor.bytesAsInt());
 
         this.compression = SETTING_HTTP_COMPRESSION.get(settings);
         this.compressionLevel = SETTING_HTTP_COMPRESSION_LEVEL.get(settings);
@@ -253,9 +238,8 @@ public Netty4HttpServerTransport(Settings settings, NetworkService networkServic
         this.maxContentLength = maxContentLength;
 
         logger.debug("using max_chunk_size[{}], max_header_size[{}], max_initial_line_length[{}], max_content_length[{}], " +
-                "receive_predictor[{}->{}], pipelining[{}], pipelining_max_events[{}]",
-            maxChunkSize, maxHeaderSize, maxInitialLineLength, this.maxContentLength,
-            receivePredictorMin, receivePredictorMax, pipelining, pipeliningMaxEvents);
+                "receive_predictor[{}], pipelining[{}], pipelining_max_events[{}]",
+            maxChunkSize, maxHeaderSize, maxInitialLineLength, this.maxContentLength, receivePredictor, pipelining, pipeliningMaxEvents);
     }
 
     public Settings settings() {

modules/transport-netty4/src/main/java/org/elasticsearch/transport/Netty4Plugin.java

@@ -56,8 +56,6 @@ public List<Setting<?>> getSettings() {
             Netty4HttpServerTransport.SETTING_HTTP_NETTY_MAX_COMPOSITE_BUFFER_COMPONENTS,
             Netty4HttpServerTransport.SETTING_HTTP_WORKER_COUNT,
             Netty4HttpServerTransport.SETTING_HTTP_NETTY_RECEIVE_PREDICTOR_SIZE,
-            Netty4HttpServerTransport.SETTING_HTTP_NETTY_RECEIVE_PREDICTOR_MIN,
-            Netty4HttpServerTransport.SETTING_HTTP_NETTY_RECEIVE_PREDICTOR_MAX,
             Netty4Transport.WORKER_COUNT,
             Netty4Transport.NETTY_RECEIVE_PREDICTOR_SIZE,
             Netty4Transport.NETTY_RECEIVE_PREDICTOR_MIN,