[grid] limit the number of websocket connections per session

java/src/org/openqa/selenium/grid/node/Node.java

@@ -101,6 +101,12 @@
  * by {@code sessionId}. This returns a boolean.</td>
  * </tr>
  * <tr>
+ * <td>POST</td>
+ * <td>/se/grid/node/connection/{sessionId}</td>
+ * <td>Allows the node to be ask about whether or not new websocket connections are allowed for the {@link Session}
+ * identified by {@code sessionId}. This returns a boolean.</td>
+ * </tr>
+ * <tr>
  * <td>*</td>
  * <td>/session/{sessionId}/*</td>
  * <td>The request is forwarded to the {@link Session} identified by {@code sessionId}. When the
@@ -172,6 +178,9 @@ protected Node(
             get("/se/grid/node/owner/{sessionId}")
                 .to(params -> new IsSessionOwner(this, sessionIdFrom(params)))
                 .with(spanDecorator("node.is_session_owner").andThen(requiresSecret)),
+            post("/se/grid/node/connection/{sessionId}")
+                .to(params -> new TryAcquireConnection(this, sessionIdFrom(params)))
+                .with(spanDecorator("node.is_session_owner").andThen(requiresSecret)),
             delete("/se/grid/node/session/{sessionId}")
                 .to(params -> new StopNodeSession(this, sessionIdFrom(params)))
                 .with(spanDecorator("node.stop_session").andThen(requiresSecret)),
@@ -244,6 +253,8 @@ public TemporaryFilesystem getDownloadsFilesystem(UUID uuid) throws IOException
 
   public abstract boolean isSessionOwner(SessionId id);
 
+  public abstract boolean tryAcquireConnection(SessionId id);
+
   public abstract boolean isSupporting(Capabilities capabilities);
 
   public abstract NodeStatus getStatus();

java/src/org/openqa/selenium/grid/node/ProxyNodeWebsockets.java

@@ -94,6 +94,13 @@ public Optional<Consumer<Message>> apply(String uri, Consumer<Message> downstrea
       return Optional.empty();
     }
 
+    // ensure one session does not open to many connections, this might have a negative impact on
+    // the grid health
+    if (!node.tryAcquireConnection(id)) {
+      LOG.warning("Too many websocket connections initiated by " + id);
+      return Optional.empty();
+    }
+
     Session session = node.getSession(id);
     Capabilities caps = session.getCapabilities();
     LOG.fine("Scanning for endpoint: " + caps);

java/src/org/openqa/selenium/grid/node/TryAcquireConnection.java

@@ -0,0 +1,45 @@
+// Licensed to the Software Freedom Conservancy (SFC) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The SFC licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+package org.openqa.selenium.grid.node;
+
+import static org.openqa.selenium.remote.http.Contents.asJson;
+
+import com.google.common.collect.ImmutableMap;
+import java.io.UncheckedIOException;
+import org.openqa.selenium.internal.Require;
+import org.openqa.selenium.remote.SessionId;
+import org.openqa.selenium.remote.http.HttpHandler;
+import org.openqa.selenium.remote.http.HttpRequest;
+import org.openqa.selenium.remote.http.HttpResponse;
+
+class TryAcquireConnection implements HttpHandler {
+
+  private final Node node;
+  private final SessionId id;
+
+  TryAcquireConnection(Node node, SessionId id) {
+    this.node = Require.nonNull("Node", node);
+    this.id = Require.nonNull("Session id", id);
+  }
+
+  @Override
+  public HttpResponse execute(HttpRequest req) throws UncheckedIOException {
+    return new HttpResponse()
+        .setContent(asJson(ImmutableMap.of("value", node.tryAcquireConnection(id))));
+  }
+}

java/src/org/openqa/selenium/grid/node/config/NodeFlags.java

@@ -18,6 +18,7 @@
 package org.openqa.selenium.grid.node.config;
 
 import static org.openqa.selenium.grid.config.StandardGridRoles.NODE_ROLE;
+import static org.openqa.selenium.grid.node.config.NodeOptions.DEFAULT_CONNECTION_LIMIT;
 import static org.openqa.selenium.grid.node.config.NodeOptions.DEFAULT_DETECT_DRIVERS;
 import static org.openqa.selenium.grid.node.config.NodeOptions.DEFAULT_DRAIN_AFTER_SESSION_COUNT;
 import static org.openqa.selenium.grid.node.config.NodeOptions.DEFAULT_ENABLE_BIDI;
@@ -77,6 +78,14 @@ public class NodeFlags implements HasRoles {
   @ConfigValue(section = NODE_SECTION, name = "session-timeout", example = "60")
   public int sessionTimeout = DEFAULT_SESSION_TIMEOUT;
 
+  @Parameter(
+      names = {"--connection-limit-per-session"},
+      description =
+          "Let X be the maximum number of websocket connections per session.This will ensure one"
+              + " session is not able to exhaust the connection limit of the host")
+  @ConfigValue(section = NODE_SECTION, name = "connection-limit-per-session", example = "8")
+  public int connectionLimitPerSession = DEFAULT_CONNECTION_LIMIT;
+
   @Parameter(
       names = {"--detect-drivers"},
       arity = 1,

java/src/org/openqa/selenium/grid/node/config/NodeOptions.java

@@ -73,6 +73,7 @@ public class NodeOptions {
   public static final int DEFAULT_HEARTBEAT_PERIOD = 60;
   public static final int DEFAULT_SESSION_TIMEOUT = 300;
   public static final int DEFAULT_DRAIN_AFTER_SESSION_COUNT = 0;
+  public static final int DEFAULT_CONNECTION_LIMIT = 10;
   public static final boolean DEFAULT_ENABLE_CDP = true;
   public static final boolean DEFAULT_ENABLE_BIDI = true;
   static final String NODE_SECTION = "node";
@@ -262,6 +263,15 @@ public int getMaxSessions() {
     return Math.min(maxSessions, DEFAULT_MAX_SESSIONS);
   }
 
+  public int getConnectionLimitPerSession() {
+    int connectionLimit =
+        config
+            .getInt(NODE_SECTION, "connection-limit-per-session")
+            .orElse(DEFAULT_CONNECTION_LIMIT);
+    Require.positive("Session connection limit", connectionLimit);
+    return connectionLimit;
+  }
+
   public Duration getSessionTimeout() {
     // If the user sets 10s or less, we default to 10s.
     int seconds =

java/src/org/openqa/selenium/grid/node/k8s/OneShotNode.java

@@ -34,6 +34,7 @@
 import java.util.Optional;
 import java.util.ServiceLoader;
 import java.util.UUID;
+import java.util.concurrent.atomic.AtomicInteger;
 import java.util.logging.Logger;
 import java.util.stream.StreamSupport;
 import org.openqa.selenium.Capabilities;
@@ -98,6 +99,8 @@ public class OneShotNode extends Node {
   private final Duration heartbeatPeriod;
   private final URI gridUri;
   private final UUID slotId = UUID.randomUUID();
+  private final int connectionLimitPerSession;
+  private final AtomicInteger connectionCounter = new AtomicInteger();
   private RemoteWebDriver driver;
   private SessionId sessionId;
   private HttpClient client;
@@ -114,14 +117,16 @@ private OneShotNode(
       URI uri,
       URI gridUri,
       Capabilities stereotype,
-      WebDriverInfo driverInfo) {
+      WebDriverInfo driverInfo,
+      int connectionLimitPerSession) {
     super(tracer, id, uri, registrationSecret, Require.positive(sessionTimeout));
 
     this.heartbeatPeriod = heartbeatPeriod;
     this.events = Require.nonNull("Event bus", events);
     this.gridUri = Require.nonNull("Public Grid URI", gridUri);
     this.stereotype = ImmutableCapabilities.copyOf(Require.nonNull("Stereotype", stereotype));
     this.driverInfo = Require.nonNull("Driver info", driverInfo);
+    this.connectionLimitPerSession = connectionLimitPerSession;
 
     new JMXHelper().register(this);
   }
@@ -177,7 +182,8 @@ public static Node create(Config config) {
             .getPublicGridUri()
             .orElseThrow(() -> new ConfigException("Unable to determine public grid address")),
         stereotype,
-        driverInfo);
+        driverInfo,
+        nodeOptions.getConnectionLimitPerSession());
   }
 
   @Override
@@ -357,6 +363,11 @@ public boolean isSessionOwner(SessionId id) {
     return driver != null && sessionId.equals(id);
   }
 
+  @Override
+  public boolean tryAcquireConnection(SessionId id) {
+    return sessionId.equals(id) && connectionLimitPerSession > connectionCounter.getAndIncrement();
+  }
+
   @Override
   public boolean isSupporting(Capabilities capabilities) {
     return driverInfo.isSupporting(capabilities);

java/src/org/openqa/selenium/grid/node/local/LocalNode.java

@@ -59,6 +59,7 @@
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicLong;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 import java.util.stream.Collectors;
@@ -127,6 +128,7 @@ public class LocalNode extends Node {
   private final int configuredSessionCount;
   private final boolean cdpEnabled;
   private final boolean managedDownloadsEnabled;
+  private final int connectionLimitPerSession;
 
   private final boolean bidiEnabled;
   private final AtomicBoolean drainAfterSessions = new AtomicBoolean();
@@ -153,7 +155,8 @@ protected LocalNode(
       Duration heartbeatPeriod,
       List<SessionSlot> factories,
       Secret registrationSecret,
-      boolean managedDownloadsEnabled) {
+      boolean managedDownloadsEnabled,
+      int connectionLimitPerSession) {
     super(
         tracer,
         new NodeId(UUID.randomUUID()),
@@ -176,6 +179,7 @@ protected LocalNode(
     this.cdpEnabled = cdpEnabled;
     this.bidiEnabled = bidiEnabled;
     this.managedDownloadsEnabled = managedDownloadsEnabled;
+    this.connectionLimitPerSession = connectionLimitPerSession;
 
     this.healthCheck =
         healthCheck == null
@@ -579,6 +583,24 @@ public boolean isSessionOwner(SessionId id) {
     return currentSessions.getIfPresent(id) != null;
   }
 
+  @Override
+  public boolean tryAcquireConnection(SessionId id) throws NoSuchSessionException {
+    SessionSlot slot = currentSessions.getIfPresent(id);
+
+    if (slot == null) {
+      return false;
+    }
+
+    if (connectionLimitPerSession == -1) {
+      // no limit
+      return true;
+    }
+
+    AtomicLong counter = slot.getConnectionCounter();
+
+    return connectionLimitPerSession > counter.getAndIncrement();
+  }
+
   @Override
   public Session getSession(SessionId id) throws NoSuchSessionException {
     Require.nonNull("Session ID", id);
@@ -987,6 +1009,7 @@ public static class Builder {
     private HealthCheck healthCheck;
     private Duration heartbeatPeriod = Duration.ofSeconds(NodeOptions.DEFAULT_HEARTBEAT_PERIOD);
     private boolean managedDownloadsEnabled = false;
+    private int connectionLimitPerSession = -1;
 
     private Builder(Tracer tracer, EventBus bus, URI uri, URI gridUri, Secret registrationSecret) {
       this.tracer = Require.nonNull("Tracer", tracer);
@@ -1041,6 +1064,11 @@ public Builder enableManagedDownloads(boolean enable) {
       return this;
     }
 
+    public Builder connectionLimitPerSession(int connectionLimitPerSession) {
+      this.connectionLimitPerSession = connectionLimitPerSession;
+      return this;
+    }
+
     public LocalNode build() {
       return new LocalNode(
           tracer,
@@ -1057,7 +1085,8 @@ public LocalNode build() {
           heartbeatPeriod,
           factories.build(),
           registrationSecret,
-          managedDownloadsEnabled);
+          managedDownloadsEnabled,
+          connectionLimitPerSession);
     }
 
     public Advanced advanced() {

java/src/org/openqa/selenium/grid/node/local/LocalNodeFactory.java

@@ -70,7 +70,8 @@ public static Node create(Config config) {
             .enableCdp(nodeOptions.isCdpEnabled())
             .enableBiDi(nodeOptions.isBiDiEnabled())
             .enableManagedDownloads(nodeOptions.isManagedDownloadsEnabled())
-            .heartbeatPeriod(nodeOptions.getHeartbeatPeriod());
+            .heartbeatPeriod(nodeOptions.getHeartbeatPeriod())
+            .connectionLimitPerSession(nodeOptions.getConnectionLimitPerSession());
 
     List<DriverService.Builder<?, ?>> builders = new ArrayList<>();
     ServiceLoader.load(DriverService.Builder.class).forEach(builders::add);

java/src/org/openqa/selenium/grid/node/local/SessionSlot.java

@@ -21,6 +21,7 @@
 import java.util.ServiceLoader;
 import java.util.UUID;
 import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicLong;
 import java.util.function.Function;
 import java.util.function.Predicate;
 import java.util.logging.Level;
@@ -59,6 +60,7 @@ public class SessionSlot
   private final AtomicBoolean reserved = new AtomicBoolean(false);
   private final boolean supportingCdp;
   private final boolean supportingBiDi;
+  private final AtomicLong connectionCounter;
   private ActiveSession currentSession;
 
   public SessionSlot(EventBus bus, Capabilities stereotype, SessionFactory factory) {
@@ -68,6 +70,7 @@ public SessionSlot(EventBus bus, Capabilities stereotype, SessionFactory factory
     this.factory = Require.nonNull("Session factory", factory);
     this.supportingCdp = isSlotSupportingCdp(this.stereotype);
     this.supportingBiDi = isSlotSupportingBiDi(this.stereotype);
+    this.connectionCounter = new AtomicLong();
   }
 
   public UUID getId() {
@@ -112,6 +115,7 @@ public void stop() {
       LOG.log(Level.WARNING, "Unable to cleanly close session", e);
     }
     currentSession = null;
+    connectionCounter.set(0);
     release();
     bus.fire(new SessionClosedEvent(id));
     LOG.info(String.format("Stopping session %s", id));
@@ -148,6 +152,7 @@ public Either<WebDriverException, ActiveSession> apply(CreateSessionRequest sess
       if (possibleSession.isRight()) {
         ActiveSession session = possibleSession.right();
         currentSession = session;
+        connectionCounter.set(0);
         return Either.right(session);
       } else {
         return Either.left(possibleSession.left());
@@ -185,4 +190,8 @@ public boolean hasRelayFactory() {
   public boolean isRelayServiceUp() {
     return hasRelayFactory() && ((RelaySessionFactory) factory).isServiceUp();
   }
+
+  public AtomicLong getConnectionCounter() {
+    return connectionCounter;
+  }
 }

java/src/org/openqa/selenium/grid/node/remote/RemoteNode.java

@@ -174,6 +174,18 @@ public boolean isSessionOwner(SessionId id) {
     return Boolean.TRUE.equals(Values.get(res, Boolean.class));
   }
 
+  @Override
+  public boolean tryAcquireConnection(SessionId id) {
+    Require.nonNull("Session ID", id);
+
+    HttpRequest req = new HttpRequest(POST, "/se/grid/node/connection/" + id);
+    HttpTracing.inject(tracer, tracer.getCurrentContext(), req);
+
+    HttpResponse res = client.with(addSecret).execute(req);
+
+    return Boolean.TRUE.equals(Values.get(res, Boolean.class));
+  }
+
   @Override
   public Session getSession(SessionId id) throws NoSuchSessionException {
     Require.nonNull("Session ID", id);

java/test/org/openqa/selenium/grid/distributor/AddingNodesTest.java

@@ -445,6 +445,11 @@ public boolean isSessionOwner(SessionId id) {
       return running != null && running.getId().equals(id);
     }
 
+    @Override
+    public boolean tryAcquireConnection(SessionId id) {
+      return false;
+    }
+
     @Override
     public boolean isSupporting(Capabilities capabilities) {
       return Objects.equals("cake", capabilities.getCapability("cheese"));