Make http header list size configurable in HTTP client for HTTP2 (#12172)

Description

This PR adds configurable maxHeaderListSize property to HTTP client configuration for HTTP2.

    Added maxHeaderListSize configuration property with getter/setter methods.
    Updated Http2FrameCodec instantiation to use the configurable header list size.

Considerations

    Can be configured via micronaut.http.client.http2.max-header-list-size property.

Author: Pavlov7

http-client-core/src/main/java/io/micronaut/http/client/HttpClientConfiguration.java

@@ -1274,12 +1274,20 @@ public static class Http2ClientConfiguration {
          */
         public static final String PREFIX = "http2";
 
+        /**
+         * The default max header list size in bytes.
+         */
+        @SuppressWarnings("WeakerAccess")
+        public static final int DEFAULT_MAX_HEADER_LIST_SIZE = 8192;
+
         private Duration pingIntervalRead = null;
 
         private Duration pingIntervalWrite = null;
 
         private Duration pingIntervalIdle = null;
 
+        private int maxHeaderListSize = DEFAULT_MAX_HEADER_LIST_SIZE;
+
         /**
          * For HTTP/2 connections, the interval from the last inbound message to when an automated ping
          * should be sent. This can be used to keep low-traffic connections alive.
@@ -1342,6 +1350,25 @@ public Duration getPingIntervalIdle() {
         public void setPingIntervalIdle(@Nullable Duration pingIntervalIdle) {
             this.pingIntervalIdle = pingIntervalIdle;
         }
+
+        /**
+         * [available in the Netty HTTP client].
+         *
+         * @return The maximum allowed compressed header list size (in bytes) after decompression
+         * using HPACK (the HTTP/2 header compression algorithm).
+         */
+        public int getMaxHeaderListSize() {
+            return maxHeaderListSize;
+        }
+
+        /**
+         * Sets the maximum header list size the client can handle. Default value ({@value io.micronaut.http.client.HttpClientConfiguration.Http2ClientConfiguration#DEFAULT_MAX_HEADER_LIST_SIZE}).
+         *
+         * @param maxHeaderListSize The maximum header list size the client can handle
+         */
+        public void setMaxHeaderListSize(@ReadableBytes int maxHeaderListSize) {
+            this.maxHeaderListSize = maxHeaderListSize;
+        }
     }
 
     /**

http-client/src/main/java/io/micronaut/http/client/netty/ConnectionManager.java

@@ -81,6 +81,7 @@
 import io.netty.handler.codec.http2.Http2MultiplexActiveStreamsException;
 import io.netty.handler.codec.http2.Http2MultiplexHandler;
 import io.netty.handler.codec.http2.Http2PingFrame;
+import io.netty.handler.codec.http2.Http2Settings;
 import io.netty.handler.codec.http2.Http2SettingsAckFrame;
 import io.netty.handler.codec.http2.Http2SettingsFrame;
 import io.netty.handler.codec.http2.Http2StreamChannel;
@@ -654,7 +655,13 @@ final <V, C extends Future<V>> void withPropagation(Future<? extends V> channelF
     }
 
     private Http2FrameCodec makeFrameCodec() {
-        Http2FrameCodecBuilder builder = Http2FrameCodecBuilder.forClient();
+        Http2Settings defaultSettings = Http2Settings.defaultSettings();
+
+        defaultSettings.maxHeaderListSize(configuration.getHttp2Configuration().getMaxHeaderListSize());
+
+        Http2FrameCodecBuilder builder = Http2FrameCodecBuilder.forClient()
+            .initialSettings(defaultSettings);
+
         configuration.getLogLevel().ifPresent(logLevel -> {
             try {
                 final LogLevel nettyLevel =