Handle race condition on accessing session info

src/main/java/org/jlab/epics2web/controller/WebConsole.java

@@ -8,9 +8,9 @@
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
-import javax.websocket.Session;
 import org.jlab.epics2web.Application;
 import org.jlab.epics2web.epics.ChannelMonitor;
+import org.jlab.epics2web.websocket.SessionInfo;
 import org.jlab.epics2web.websocket.WebSocketSessionManager;
 import org.jlab.epics2web.epics.ChannelManager;
 
@@ -40,7 +40,7 @@ protected void doGet(HttpServletRequest request, HttpServletResponse response)
 
 
         Map<String, ChannelMonitor> monitorMap = channelManager.getMonitorMap();
-        Map<Session, Set<String>> clientMap = sessionManager.getClientMap();
+        Map<SessionInfo, Set<String>> clientMap = sessionManager.getClientMap();
 
         request.setAttribute("monitorMap", monitorMap);
         request.setAttribute("clientMap", clientMap);

src/main/java/org/jlab/epics2web/epics/ChannelManager.java

@@ -382,7 +382,7 @@ public Map<String, ChannelMonitor> getMonitorMap() {
      *
      * @return The listener to PVs map
      */
-    public Map<PvListener, Set<String>> getClientMap() {
+    public Map<PvListener, Set<String>> getListenerMap() {
         return Collections.unmodifiableMap(clientMap);
     }
 }

src/main/java/org/jlab/epics2web/websocket/SessionInfo.java

@@ -0,0 +1,43 @@
+package org.jlab.epics2web.websocket;
+
+/**
+ * This class provides a snapshot of websocket information that will not throw Exceptions if you try to interrogate it
+ * after the session happens to have closed.  There is a race condition if you hand a list of javax.websocket.Session
+ * objects to a debug console for example as if the session happens to close between the time you return it and the
+ * time the debug console calls the userProperties method for example you get an exception.
+ */
+public class SessionInfo {
+    private String id;
+    private String ip;
+    private String name;
+    private String agent;
+    private long droppedMessageCount;
+
+    public SessionInfo(String id, String ip, String name, String agent, long droppedMessageCount) {
+        this.id = id;
+        this.ip = ip;
+        this.name = name;
+        this.agent = agent;
+        this.droppedMessageCount = droppedMessageCount;
+    }
+
+    public String getId() {
+        return id;
+    }
+
+    public String getIp() {
+        return ip;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public String getAgent() {
+        return agent;
+    }
+
+    public long getDroppedMessageCount() {
+        return droppedMessageCount;
+    }
+}

src/main/java/org/jlab/epics2web/websocket/WebSocketSessionManager.java

@@ -229,14 +229,33 @@ public void removePvs(Session session, Set<String> pvSet) {
      *
      * @return The map
      */
-    public Map<Session, Set<String>> getClientMap() {
-        Map<PvListener, Set<String>> pvMap = Application.channelManager.getClientMap();
-        Map<Session, Set<String>> clientMap = new HashMap<>();
+    public Map<SessionInfo, Set<String>> getClientMap() {
+        Map<PvListener, Set<String>> pvMap = Application.channelManager.getListenerMap();
+        Map<SessionInfo, Set<String>> clientMap = new HashMap<>();
 
         for (Session session : listenerMap.keySet()) {
             WebSocketSessionMonitor listener = listenerMap.get(session);
             Set<String> pvSet = pvMap.get(listener);
-            clientMap.put(session, pvSet);
+
+            if(session.isOpen()) {
+                String id = null;
+
+                try {
+                    id = session.getId();
+                    String ip = (String)session.getUserProperties().get("ip");
+                    String name = (String)session.getUserProperties().get("name");
+                    String agent = (String)session.getUserProperties().get("agent");
+                    AtomicLong droppedMessageCount = (AtomicLong)session.getUserProperties().get("droppedMessageCount");
+
+                    SessionInfo info = new SessionInfo(id, ip, name, agent, droppedMessageCount.get());
+
+                    clientMap.put(info, pvSet);
+                } catch(Exception e) {
+                    // Even id may be null if closed before getId() called.  Oh well.
+                    LOGGER.log(Level.FINEST, "Session '{0}' closed while preparing info report", id);
+                    // Ignore
+                }
+            }
         }
 
         return clientMap;

src/main/webapp/WEB-INF/views/console.jsp

@@ -49,11 +49,11 @@
                 <c:forEach items="${clientMap}" var="client">
                     <tr>
                         <td><c:out value="${client.key.id}"/></td>
-                        <td><c:out value="${client.key.userProperties.ip eq null ? client.key.remoteAddr : client.key.userProperties.ip}"/></td>
-                        <td><c:out value="${client.key.userProperties.agent}"/></td>
-                        <td><c:out value="${client.key.userProperties.name}"/></td>
+                        <td><c:out value="${client.key.ip}"/></td>
+                        <td><c:out value="${client.key.agent}"/></td>
+                        <td><c:out value="${client.key.name}"/></td>
                         <td>(${client.value == null ? '0' : client.value.size()}) <c:out value="${client.value}"/></td>
-                        <td><fmt:formatNumber value="${client.key.userProperties.droppedMessageCount}"/></td>
+                        <td><fmt:formatNumber value="${client.key.droppedMessageCount}"/></td>
                     </tr>
                 </c:forEach>
             </tbody>