[Master] Enforce HTTP/2 maxConcurrentStreams limit on server

README.md

@@ -107,6 +107,26 @@ built-in support for basic authentication, JWT authentication, and OAuth2 authen
 In addition to that, supports both the HTTP/1.1 and HTTP2 protocols and connection keep-alive, content
 chunking, HTTP caching, data compression/decompression, payload binding, and authorization can be highlighted as the features of a `Service`.
 
+#### HTTP/2 Stream Concurrency
+
+Each HTTP/2 connection can carry multiple requests simultaneously using independent streams. To prevent a single
+connection from opening an unbounded number of streams and exhausting server memory, the listener enforces a limit
+of **100 concurrent streams per connection** by default. This is the value recommended by RFC 7540 and consistent
+with other widely-used HTTP/2 server implementations such as Nginx and Envoy.
+
+When a client reaches this limit on a connection, it will automatically open an additional connection rather than
+stalling, so normal traffic is unaffected for typical workloads.
+
+The server-side stream limit can be tuned per listener using `http2MaxActiveStreams` in `ListenerConfiguration`:
+
+```ballerina
+listener http:Listener h2Listener = new (9090, {
+    http2MaxActiveStreams: 500
+});
+```
+
+When not set, the listener defaults to 100.
+
 ## Issues and projects 
 
 Issues and Projects tabs are disabled for this repository as this is part of the Ballerina Standard Library. To report bugs, request new features, start new discussions, view project boards, etc. please visit Ballerina Standard Library [parent repository](https://github.com/ballerina-platform/ballerina-standard-library). 

ballerina/README.md

@@ -97,3 +97,23 @@ built-in support for basic authentication, JWT authentication, and OAuth2 authen
 
 In addition to that, supports both the HTTP/1.1 and HTTP2 protocols and connection keep-alive, content 
 chunking, HTTP caching, data compression/decompression, payload binding, and authorization can be highlighted as the features of a `Service`.
+
+#### HTTP/2 Stream Concurrency
+
+Each HTTP/2 connection can carry multiple requests simultaneously using independent streams. To prevent a single
+connection from opening an unbounded number of streams and exhausting server memory, the listener enforces a limit
+of **100 concurrent streams per connection** by default. This is the value recommended by RFC 7540 and consistent
+with other widely-used HTTP/2 server implementations such as Nginx and Envoy.
+
+When a client reaches this limit on a connection, it will automatically open an additional connection rather than
+stalling, so normal traffic is unaffected for typical workloads.
+
+The server-side stream limit can be tuned per listener using `http2MaxActiveStreams` in `ListenerConfiguration`:
+
+```ballerina
+listener http:Listener h2Listener = new (9090, {
+    http2MaxActiveStreams: 500
+});
+```
+
+When not set, the listener defaults to 100.

ballerina/http_service_endpoint.bal

@@ -148,6 +148,8 @@ public type Local record {|
 # + gracefulStopTimeout - Grace period of time in seconds for listener gracefulStop
 # + socketConfig - Provides settings related to server socket configuration
 # + http2InitialWindowSize - Configuration to change the initial window size in HTTP/2
+# + http2MaxActiveStreams - Maximum concurrent HTTP/2 streams per connection advertised to clients.
+#                          Defaults to 100
 # + minIdleTimeInStaleState - Minimum time in seconds for a connection to be kept open which has received a GOAWAY.
 #                             This only applies for HTTP/2. Default value is 5 minutes. If the value is set to -1,
 #                             the connection will be closed after all in-flight streams are completed
@@ -164,6 +166,7 @@ public type ListenerConfiguration record {|
     decimal gracefulStopTimeout = DEFAULT_GRACEFULSTOP_TIMEOUT;
     ServerSocketConfig socketConfig = {};
     int http2InitialWindowSize = 65535;
+    int http2MaxActiveStreams = 100;
     decimal minIdleTimeInStaleState = 300;
     decimal timeBetweenStaleEviction = 30;
 |};

native/src/main/java/io/ballerina/stdlib/http/api/HttpConstants.java

@@ -444,6 +444,8 @@ public final class HttpConstants {
     public static final BString ENDPOINT_CONFIG_GRACEFUL_STOP_TIMEOUT = StringUtils.fromString("gracefulStopTimeout");
     public static final BString ENDPOINT_CONFIG_HTTP2_INITIAL_WINDOW_SIZE = StringUtils
             .fromString("http2InitialWindowSize");
+    public static final BString ENDPOINT_CONFIG_HTTP2_MAX_ACTIVE_STREAMS = StringUtils
+            .fromString("http2MaxActiveStreams");
     public static final BString ENDPOINT_CONFIG_IDLE_TIME_STALE_STATE = StringUtils.fromString(
             "minIdleTimeInStaleState");
     public static final BString ENDPOINT_CONFIG_TIME_BETWEEN_STALE_CHECK_RUNS = StringUtils.fromString(

native/src/main/java/io/ballerina/stdlib/http/api/HttpUtil.java

@@ -134,6 +134,7 @@
 import static io.ballerina.stdlib.http.api.HttpConstants.ANN_CONFIG_ATTR_SSL_ENABLED_PROTOCOLS;
 import static io.ballerina.stdlib.http.api.HttpConstants.CREATE_INTERCEPTORS_FUNCTION_NAME;
 import static io.ballerina.stdlib.http.api.HttpConstants.ENDPOINT_CONFIG_HTTP2_INITIAL_WINDOW_SIZE;
+import static io.ballerina.stdlib.http.api.HttpConstants.ENDPOINT_CONFIG_HTTP2_MAX_ACTIVE_STREAMS;
 import static io.ballerina.stdlib.http.api.HttpConstants.HTTP_HEADERS;
 import static io.ballerina.stdlib.http.api.HttpConstants.RESOLVED_REQUESTED_URI;
 import static io.ballerina.stdlib.http.api.HttpConstants.RESPONSE_CACHE_CONTROL;
@@ -1583,6 +1584,8 @@ public static ListenerConfiguration getListenerConfig(long port, BMap endpointCo
         listenerConfiguration.setPipeliningEnabled(true); //Pipelining is enabled all the time
         listenerConfiguration.setHttp2InitialWindowSize(endpointConfig
                 .getIntValue(ENDPOINT_CONFIG_HTTP2_INITIAL_WINDOW_SIZE).intValue());
+        listenerConfiguration.setHttp2MaxConcurrentStreams(
+                (int) endpointConfig.getIntValue(ENDPOINT_CONFIG_HTTP2_MAX_ACTIVE_STREAMS));
 
         double minIdleTimeInStaleState =
                 ((BDecimal) endpointConfig.get(HttpConstants.ENDPOINT_CONFIG_IDLE_TIME_STALE_STATE)).floatValue();

native/src/main/java/io/ballerina/stdlib/http/transport/contract/config/ListenerConfiguration.java

@@ -64,6 +64,7 @@ public static ListenerConfiguration getDefault() {
     private boolean socketReuse;
     private boolean socketKeepAlive;
     private int http2InitialWindowSize = 65535;
+    private int http2MaxActiveStreams;
     private long minIdleTimeInStaleState = 3000000;
     private long timeBetweenStaleEviction = 30000;
 
@@ -285,6 +286,14 @@ public void setHttp2InitialWindowSize(int http2InitialWindowSize) {
         this.http2InitialWindowSize = http2InitialWindowSize;
     }
 
+    public int getHttp2MaxConcurrentStreams() {
+        return http2MaxActiveStreams;
+    }
+
+    public void setHttp2MaxConcurrentStreams(int http2MaxActiveStreams) {
+        this.http2MaxActiveStreams = http2MaxActiveStreams;
+    }
+
     public void setTimeBetweenStaleEviction(long timeBetweenStaleEviction) {
         this.timeBetweenStaleEviction = timeBetweenStaleEviction;
     }

native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/DefaultHttpWsConnectorFactory.java

@@ -91,6 +91,7 @@ public ServerConnector createServerConnector(ServerBootstrapConfiguration server
         if (Constants.HTTP_2_0.equals(listenerConfig.getVersion())) {
             serverConnectorBootstrap.setHttp2Enabled(true);
             serverConnectorBootstrap.setHttp2InitialWindowSize(listenerConfig.getHttp2InitialWindowSize());
+            serverConnectorBootstrap.setHttp2MaxConcurrentStreams(listenerConfig.getHttp2MaxConcurrentStreams());
             serverConnectorBootstrap.setMinIdleTimeInStaleState(listenerConfig.getMinIdleTimeInStaleState());
             serverConnectorBootstrap.setTimeBetweenStaleEviction(listenerConfig.getTimeBetweenStaleEviction());
         }

native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/listener/HttpServerChannelInitializer.java

@@ -113,6 +113,7 @@ public class HttpServerChannelInitializer extends ChannelInitializer<SocketChann
     private EventExecutorGroup pipeliningGroup;
     private boolean webSocketCompressionEnabled;
     private int http2InitialWindowSize;
+    private int http2MaxActiveStreams = 100;
     private long minIdleTimeInStaleState;
     private long timeBetweenStaleEviction;
     private final BlockingQueue<Http2SourceHandler> http2StaleSourceHandlers = new LinkedBlockingQueue<>();
@@ -261,7 +262,7 @@ private void configureH2cPipeline(ChannelPipeline pipeline) {
         // Add handler to handle http2 requests without an upgrade
         pipeline.addLast(new Http2WithPriorKnowledgeHandler(
                 interfaceId, serverName, serverConnectorFuture, this, allChannels, listenerChannels,
-                reqSizeValidationConfig.getMaxHeaderSize(), http2InitialWindowSize));
+                reqSizeValidationConfig.getMaxHeaderSize(), http2InitialWindowSize, http2MaxActiveStreams));
         // Add http2 upgrade decoder and upgrade handler
         final HttpServerCodec sourceCodec = new HttpServerCodec(reqSizeValidationConfig.getMaxInitialLineLength(),
                                                                 reqSizeValidationConfig.getMaxHeaderSize(),
@@ -281,7 +282,7 @@ private void configureH2cPipeline(ChannelPipeline pipeline) {
                         new Http2SourceConnectionHandlerBuilder(
                                 interfaceId, serverConnectorFuture, serverName, this,
                                 this.allChannels, this.listenerChannels, reqSizeValidationConfig.getMaxHeaderSize(),
-                                this.http2InitialWindowSize).build());
+                                this.http2InitialWindowSize, this.http2MaxActiveStreams).build());
             } else {
                 return null;
             }
@@ -355,6 +356,10 @@ void setHttp2InitialWindowSize(int http2InitialWindowSize) {
         this.http2InitialWindowSize = http2InitialWindowSize;
     }
 
+    void setHttp2MaxConcurrentStreams(int http2MaxActiveStreams) {
+        this.http2MaxActiveStreams = http2MaxActiveStreams;
+    }
+
     void setTimeBetweenStaleEviction(long timeBetweenStaleEviction) {
         this.timeBetweenStaleEviction = timeBetweenStaleEviction;
     }
@@ -447,7 +452,7 @@ protected void configurePipeline(ChannelHandlerContext ctx, String protocol) {
                         new Http2SourceConnectionHandlerBuilder(
                                 interfaceId, serverConnectorFuture, serverName, channelInitializer,
                                 allChannels, listenerChannels, reqSizeValidationConfig.getMaxHeaderSize(),
-                                http2InitialWindowSize).build());
+                                http2InitialWindowSize, http2MaxActiveStreams).build());
             } else if (ApplicationProtocolNames.HTTP_1_1.equals(protocol)) {
                 // handles pipeline for HTTP/1.x requests after SSL handshake
                 configureHttpPipeline(ctx.pipeline(), Constants.HTTP_SCHEME);

native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/listener/ServerConnectorBootstrap.java

@@ -201,6 +201,10 @@ public void setHttp2InitialWindowSize(int http2InitialWindowSize) {
         httpServerChannelInitializer.setHttp2InitialWindowSize(http2InitialWindowSize);
     }
 
+    public void setHttp2MaxConcurrentStreams(int http2MaxActiveStreams) {
+        httpServerChannelInitializer.setHttp2MaxConcurrentStreams(http2MaxActiveStreams);
+    }
+
     public void setTimeBetweenStaleEviction(long timeBetweenStaleEviction) {
         httpServerChannelInitializer.setTimeBetweenStaleEviction(timeBetweenStaleEviction);
     }

native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/listener/http2/Http2SourceConnectionHandlerBuilder.java

@@ -54,7 +54,8 @@ public Http2SourceConnectionHandlerBuilder(String interfaceId, ServerConnectorFu
                                                ChannelGroup allChannels,
                                                ChannelGroup listenerChannels,
                                                long maxHeaderListSize,
-                                               int initialWindowSize) {
+                                               int initialWindowSize,
+                                               int maxActiveStreams) {
         this.interfaceId = interfaceId;
         this.serverConnectorFuture = serverConnectorFuture;
         this.serverName = serverName;
@@ -63,6 +64,7 @@ public Http2SourceConnectionHandlerBuilder(String interfaceId, ServerConnectorFu
         this.listenerChannels = listenerChannels;
         this.initialSettings().maxHeaderListSize(maxHeaderListSize);
         this.initialSettings().initialWindowSize(initialWindowSize);
+        this.initialSettings().maxConcurrentStreams(maxActiveStreams);
     }
 
     @Override

native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/listener/http2/Http2WithPriorKnowledgeHandler.java

@@ -49,14 +49,16 @@ public class Http2WithPriorKnowledgeHandler extends ChannelInboundHandlerAdapter
     private ChannelGroup listenerChannels;
     private long maxHeaderListSize;
     private int initialWindowSize;
+    private int maxActiveStreams;
 
     public Http2WithPriorKnowledgeHandler(String interfaceId, String serverName,
                                           ServerConnectorFuture serverConnectorFuture,
                                           HttpServerChannelInitializer serverChannelInitializer,
                                           ChannelGroup allChannels,
                                           ChannelGroup listenerChannels,
                                           long maxHeaderListSize,
-                                          int initialWindowSize) {
+                                          int initialWindowSize,
+                                          int maxActiveStreams) {
         this.interfaceId = interfaceId;
         this.serverName = serverName;
         this.serverConnectorFuture = serverConnectorFuture;
@@ -65,6 +67,7 @@ public Http2WithPriorKnowledgeHandler(String interfaceId, String serverName,
         this.listenerChannels = listenerChannels;
         this.maxHeaderListSize = maxHeaderListSize;
         this.initialWindowSize = initialWindowSize;
+        this.maxActiveStreams = maxActiveStreams;
     }
 
     @Override
@@ -83,7 +86,8 @@ public void channelRead(ChannelHandlerContext ctx, Object msg) {
                         Constants.HTTP2_SOURCE_CONNECTION_HANDLER,
                         new Http2SourceConnectionHandlerBuilder(
                                 interfaceId, serverConnectorFuture, serverName, serverChannelInitializer,
-                                allChannels, listenerChannels, maxHeaderListSize, initialWindowSize).build());
+                                allChannels, listenerChannels, maxHeaderListSize, initialWindowSize,
+                                maxActiveStreams).build());
                 safelyRemoveHandlers(pipeline, Constants.HTTP2_UPGRADE_HANDLER,
                         Constants.HTTP_COMPRESSOR, Constants.HTTP_TRACE_LOG_HANDLER);
             }