GUAC-830: Add ConfigurableGuacamoleTunnelService.

extensions/guacamole-auth-jdbc/modules/guacamole-auth-jdbc-base/src/main/java/org/glyptodon/guacamole/auth/jdbc/tunnel/ConfigurableGuacamoleTunnelService.java

@@ -0,0 +1,276 @@
+/*
+ * Copyright (C) 2015 Glyptodon LLC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package org.glyptodon.guacamole.auth.jdbc.tunnel;
+
+import com.google.common.collect.ConcurrentHashMultiset;
+import com.google.inject.Singleton;
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.List;
+import org.glyptodon.guacamole.GuacamoleClientTooManyException;
+import org.glyptodon.guacamole.auth.jdbc.user.AuthenticatedUser;
+import org.glyptodon.guacamole.auth.jdbc.connection.ModeledConnection;
+import org.glyptodon.guacamole.GuacamoleException;
+import org.glyptodon.guacamole.GuacamoleResourceConflictException;
+import org.glyptodon.guacamole.auth.jdbc.connectiongroup.ModeledConnectionGroup;
+
+
+/**
+ * GuacamoleTunnelService implementation which restricts concurrency for each
+ * connection and group according to a maximum number of connections and
+ * maximum number of connections per user.
+ *
+ * @author James Muehlner
+ * @author Michael Jumper
+ */
+@Singleton
+public class ConfigurableGuacamoleTunnelService
+    extends AbstractGuacamoleTunnelService {
+
+    /**
+     * Set of all currently-active user/connection pairs (seats).
+     */
+    private final ConcurrentHashMultiset<Seat> activeSeats = ConcurrentHashMultiset.<Seat>create();
+
+    /**
+     * Set of all currently-active connections.
+     */
+    private final ConcurrentHashMultiset<String> activeConnections = ConcurrentHashMultiset.<String>create();
+
+    /**
+     * Set of all currently-active user/connection group pairs (seats).
+     */
+    private final ConcurrentHashMultiset<Seat> activeGroupSeats = ConcurrentHashMultiset.<Seat>create();
+
+    /**
+     * Set of all currently-active connection groups.
+     */
+    private final ConcurrentHashMultiset<String> activeGroups = ConcurrentHashMultiset.<String>create();
+
+    /**
+     * The maximum number of connections allowed per connection by default, or
+     * zero if no default limit applies.
+     */
+    private final int connectionDefaultMaxConnections;
+
+    /**
+     * The maximum number of connections a user may have to any one connection
+     * by default, or zero if no default limit applies.
+     */
+    private final int connectionDefaultMaxConnectionsPerUser;
+
+    /**
+     * The maximum number of connections allowed per connection group by
+     * default, or zero if no default limit applies.
+     */
+    private final int connectionGroupDefaultMaxConnections;
+
+    /**
+     * The maximum number of connections a user may have to any one connection
+     * group by default, or zero if no default limit applies.
+     */
+    private final int connectionGroupDefaultMaxConnectionsPerUser;
+
+    /**
+     * Creates a new ConfigurableGuacamoleTunnelService which applies the given
+     * limitations when new connections are acquired.
+     *
+     * @param connectionDefaultMaxConnections
+     *     The maximum number of connections allowed per connection by default,
+     *     or zero if no default limit applies.
+     *
+     * @param connectionDefaultMaxConnectionsPerUser
+     *     The maximum number of connections a user may have to any one
+     *     connection by default, or zero if no default limit applies.
+     *
+     * @param connectionGroupDefaultMaxConnections
+     *     The maximum number of connections allowed per connection group by
+     *     default, or zero if no default limit applies.
+     *
+     * @param connectionGroupDefaultMaxConnectionsPerUser
+     *     The maximum number of connections a user may have to any one
+     *     connection group by default, or zero if no default limit applies.
+     */
+    public ConfigurableGuacamoleTunnelService(
+            int connectionDefaultMaxConnections,
+            int connectionDefaultMaxConnectionsPerUser,
+            int connectionGroupDefaultMaxConnections,
+            int connectionGroupDefaultMaxConnectionsPerUser) {
+
+        // Set default connection limits
+        this.connectionDefaultMaxConnections        = connectionDefaultMaxConnections;
+        this.connectionDefaultMaxConnectionsPerUser = connectionDefaultMaxConnectionsPerUser;
+
+        // Set default connection group limits
+        this.connectionGroupDefaultMaxConnections        = connectionGroupDefaultMaxConnections;
+        this.connectionGroupDefaultMaxConnectionsPerUser = connectionGroupDefaultMaxConnectionsPerUser;
+
+    }
+
+    /**
+     * Attempts to add a single instance of the given value to the given
+     * multiset without exceeding the specified maximum number of values. If
+     * the value cannot be added without exceeding the maximum, false is
+     * returned.
+     *
+     * @param <T>
+     *     The type of values contained within the multiset.
+     *
+     * @param multiset
+     *     The multiset to attempt to add a value to.
+     *
+     * @param value
+     *     The value to attempt to add.
+     *
+     * @param max
+     *     The maximum number of each distinct value that the given multiset
+     *     should hold, or zero if no limit applies.
+     *
+     * @return
+     *     true if the value was successfully added without exceeding the
+     *     specified maximum, false if the value could not be added.
+     */
+    private <T> boolean tryAdd(ConcurrentHashMultiset<T> multiset, T value, int max) {
+
+        // Repeatedly attempt to add a new value to the given multiset until we
+        // explicitly succeed or explicitly fail
+        while (true) {
+
+            // Get current number of values
+            int count = multiset.count(value);
+
+            // Bail out if the maximum has already been reached
+            if (count >= max || max == 0)
+                return false;
+
+            // Attempt to add one more value
+            if (multiset.setCount(value, count, count+1))
+                return true;
+
+            // Try again if unsuccessful
+
+        }
+
+    }
+
+    @Override
+    protected ModeledConnection acquire(AuthenticatedUser user,
+            List<ModeledConnection> connections) throws GuacamoleException {
+
+        // Get username
+        String username = user.getUser().getIdentifier();
+
+        // Sort connections in ascending order of usage
+        ModeledConnection[] sortedConnections = connections.toArray(new ModeledConnection[connections.size()]);
+        Arrays.sort(sortedConnections, new Comparator<ModeledConnection>() {
+
+            @Override
+            public int compare(ModeledConnection a, ModeledConnection b) {
+
+                return getActiveConnections(a).size()
+                     - getActiveConnections(b).size();
+
+            }
+
+        });
+
+        // Track whether acquire fails due to user-specific limits
+        boolean userSpecificFailure = true;
+
+        // Return the first unreserved connection
+        for (ModeledConnection connection : sortedConnections) {
+
+            // Attempt to aquire connection according to per-user limits
+            Seat seat = new Seat(username, connection.getIdentifier());
+            if (tryAdd(activeSeats, seat,
+                    connectionDefaultMaxConnectionsPerUser)) {
+
+                // Attempt to aquire connection according to overall limits
+                if (tryAdd(activeConnections, connection.getIdentifier(),
+                        connectionDefaultMaxConnections))
+                    return connection;
+
+                // Acquire failed - retry with next connection
+                activeSeats.remove(seat);
+
+                // Failure to acquire is not user-specific
+                userSpecificFailure = false;
+
+            }
+
+        }
+
+        // Too many connections by this user
+        if (userSpecificFailure)
+            throw new GuacamoleClientTooManyException("Cannot connect. Connection group already in use by this user.");
+
+        // Too many connections, but not necessarily due purely to this user
+        else
+            throw new GuacamoleResourceConflictException("Cannot connect. This connection is in use.");
+
+    }
+
+    @Override
+    protected void release(AuthenticatedUser user, ModeledConnection connection) {
+        activeSeats.remove(new Seat(user.getUser().getIdentifier(), connection.getIdentifier()));
+        activeConnections.remove(connection.getIdentifier());
+    }
+
+    @Override
+    protected void acquire(AuthenticatedUser user,
+            ModeledConnectionGroup connectionGroup) throws GuacamoleException {
+
+        // Get username
+        String username = user.getUser().getIdentifier();
+
+        // Attempt to aquire connection group according to per-user limits
+        Seat seat = new Seat(username, connectionGroup.getIdentifier());
+        if (tryAdd(activeGroupSeats, seat,
+                connectionGroupDefaultMaxConnectionsPerUser)) {
+
+            // Attempt to aquire connection group according to overall limits
+            if (tryAdd(activeGroups, connectionGroup.getIdentifier(),
+                    connectionGroupDefaultMaxConnections))
+                return;
+
+            // Acquire failed
+            activeGroupSeats.remove(seat);
+
+            // Failure to acquire is not user-specific
+            throw new GuacamoleResourceConflictException("Cannot connect. This connection group is in use.");
+
+        }
+
+        // Already in use by this user
+        throw new GuacamoleClientTooManyException("Cannot connect. Connection group already in use by this user.");
+
+    }
+
+    @Override
+    protected void release(AuthenticatedUser user,
+            ModeledConnectionGroup connectionGroup) {
+        activeGroupSeats.remove(new Seat(user.getUser().getIdentifier(), connectionGroup.getIdentifier()));
+        activeGroups.remove(connectionGroup.getIdentifier());
+    }
+
+}