double pendingTasks() {
            int result = 0;
            for (EventLoopGroup group : registry) {
                // Purge event loop groups that were shutdown.
                if (group.isShutdown()) {
                    remove(group);
                    continue;
                }
                for (EventExecutor eventLoop : group) {
                    if (eventLoop instanceof SingleThreadEventLoop) {
                        result += ((SingleThreadEventLoop) eventLoop).pendingTasks();
                    }
                }
            }
            return result;
        }
An actual implementation of {@link EventLoopMetrics}.
core/src/main/java/com/linecorp/armeria/common/metric/EventLoopMetrics.java