Measure Vaadin UI memory consumption by opening lots of tabs

gistfile1.txt

    @Bean
    public VaadinServiceInitListener memoryMeasure() {
        /*-
         * 1. Run app in production mode
         * 2. Open 100 browser tabs: for i in {1..100} ; do open "http://localhost:8080/"; done
         * 3. Verify UI count and wait until the memory measurement in the console has stabilized
         * 4. Close all the tabs
         * 5. Wait until new memory measurement has stabilized
         */
        AtomicInteger openUIs = new AtomicInteger();

        return serviceInit -> {
            VaadinService service = serviceInit.getSource();
            service.addUIInitListener(uiInit -> {
                openUIs.incrementAndGet();
                uiInit.getUI().addDetachListener(detach -> {
                    openUIs.decrementAndGet();
                });
            });

            Thread thread = new Thread(() -> {
                try {
                    Runtime runtime = Runtime.getRuntime();

                    int maxUis = 0;
                    long minMemoryAfterOpening = Long.MAX_VALUE;
                    long minMemoryAfterClosing = Long.MAX_VALUE;

                    while (true) {
                        long usedMemory = runtime.totalMemory()
                                - runtime.freeMemory();
                        int uis = openUIs.get();

                        if (uis == 0 && maxUis > 0) {
                            if (usedMemory < minMemoryAfterClosing
                                    && usedMemory < minMemoryAfterOpening) {
                                System.out.println(
                                        "New record for no UIs: " + usedMemory);
                                minMemoryAfterClosing = usedMemory;

                                long diff = minMemoryAfterOpening
                                        - minMemoryAfterClosing;
                                System.out.println("Diff: " + diff);
                                System.out.println("Diff per UI: "
                                        + diff / (double) maxUis);
                            }
                        } else if (uis > maxUis) {
                            maxUis = uis;
                            minMemoryAfterOpening = usedMemory;
                        } else if (uis != 0 && uis == maxUis) {
                            if (usedMemory < minMemoryAfterOpening) {
                                System.out.println("New record for " + uis
                                        + " UIs: " + usedMemory);
                                minMemoryAfterOpening = usedMemory;
                            }
                        }

                        runtime.gc();
                        Thread.sleep(1000);
                    }
                } catch (InterruptedException e) {
                    return;
                }
            });
            thread.start();
            service.addServiceDestroyListener(destory -> thread.interrupt());
        };
    }