Do full connector tracker cleanup when the session lock is released (#9707) (#9730)

As there is no "request end" call after invoking UI.access() from a background thread,
the connector map was not earlier properly cleaned afterwards. If you toggled visibility of a
component from the background thread, the tracker state became inconsistent.

If this becomes a performance problem, it could probably be optimized to that cleanup
is done in request end and only at the end of access if not inside a request.

Backported from master
Fixes #9693

3 files changed, 9 insertions, 24 deletions

diff --git a/server/src/main/java/com/vaadin/server/VaadinService.java b/server/src/main/java/com/vaadin/server/VaadinService.java
index 75124aa6ef..e453332f02 100644
--- a/server/src/main/java/com/vaadin/server/VaadinService.java
+++ b/server/src/main/java/com/vaadin/server/VaadinService.java
@@ -1365,20 +1365,6 @@ public abstract class VaadinService implements Serializable {
                 final long duration = (System.nanoTime() - (Long) request
                         .getAttribute(REQUEST_START_TIME_ATTRIBUTE)) / 1000000;
                 session.setLastRequestDuration(duration);
-
-                // Check that connector tracker is in a consistent state here to
-                // avoid doing it multiple times for a single request
-                for (UI ui : session.getUIs()) {
-                    try {
-                        ui.getConnectorTracker().ensureCleanedAndConsistent();
-                    } catch (AssertionError e) {
-                        getLogger().log(Level.SEVERE,
-                                "Error cleaning ConnectionTracker", e);
-                    } catch (Exception e) {
-                        getLogger().log(Level.SEVERE,
-                                "Error cleaning ConnectionTracker", e);
-                    }
-                }
             } finally {
                 session.unlock();
             }
diff --git a/server/src/main/java/com/vaadin/server/VaadinSession.java b/server/src/main/java/com/vaadin/server/VaadinSession.java
index f4ebc06335..7014a5f1f5 100644
--- a/server/src/main/java/com/vaadin/server/VaadinSession.java
+++ b/server/src/main/java/com/vaadin/server/VaadinSession.java
@@ -1009,6 +1009,11 @@ public class VaadinSession implements HttpSessionBindingListener, Serializable {
                                 "Exception while cleaning connector map for ui "
                                         + ui.getUIId(),
                                 e);
+                    } catch (AssertionError e) {
+                        getLogger().log(Level.SEVERE,
+                                "Exception while cleaning connector map for ui "
+                                        + ui.getUIId(),
+                                e);
                     }
                 }
             }
diff --git a/server/src/main/java/com/vaadin/ui/ConnectorTracker.java b/server/src/main/java/com/vaadin/ui/ConnectorTracker.java
index 043c1174fb..d2b9b65764 100644
--- a/server/src/main/java/com/vaadin/ui/ConnectorTracker.java
+++ b/server/src/main/java/com/vaadin/ui/ConnectorTracker.java
@@ -272,17 +272,7 @@ public class ConnectorTracker implements Serializable {
         }
 
         cleanStreamVariables();
-    }
 
-    /**
-     * Performs expensive checks to ensure that the connector tracker is cleaned
-     * properly and in a consistent state.
-     * <p>
-     * This should only be called by the framework.
-     *
-     * @since
-     */
-    public void ensureCleanedAndConsistent() {
         // Do this expensive check only with assertions enabled
         assert isHierarchyComplete() : "The connector hierarchy is corrupted. "
                 + "Check for missing calls to super.setParent(), super.attach() and super.detach() "
@@ -315,6 +305,10 @@ public class ConnectorTracker implements Serializable {
             } else if (!uninitializedConnectors.contains(connector)
                     && !LegacyCommunicationManager
                             .isConnectorVisibleToClient(connector)) {
+                // Connector was visible to the client but is no longer (e.g.
+                // setVisible(false) has been called or SelectiveRenderer tells
+                // it's no longer shown) -> make sure that the full state is
+                // sent again when/if made visible
                 uninitializedConnectors.add(connector);
                 diffStates.remove(connector);
                 assert isRemovalSentToClient(connector) : "Connector "