tryScaleUpBy() — netty Function Reference

Source Code

common/src/main/java/io/netty/util/concurrent/AutoScalingEventExecutorChooserFactory.java lines 207–256

        private void tryScaleUpBy(int amount) {
            if (amount <= 0) {
                return;
            }

            for (;;) {
                AutoScalingState oldState = state.get();
                if (oldState.activeChildrenCount >= maxChildren) {
                    return;
                }

                int canAdd = Math.min(amount, maxChildren - oldState.activeChildrenCount);
                List<EventExecutor> wokenUp = new ArrayList<>(canAdd);
                final long startIndex = oldState.nextWakeUpIndex;

                for (int i = 0; i < executors.length; i++) {
                    EventExecutor child = executors[(int) Math.abs((startIndex + i) % executors.length)];

                    if (wokenUp.size() >= canAdd) {
                        break; // We have woken up all the threads we reserved.
                    }
                    if (child instanceof SingleThreadEventExecutor) {
                        SingleThreadEventExecutor stee = (SingleThreadEventExecutor) child;
                        if (stee.isSuspended()) {
                            stee.execute(NO_OOP_TASK);
                            wokenUp.add(stee);
                        }
                    }
                }

                if (wokenUp.isEmpty()) {
                    return;
                }

                // Create the new state.
                List<EventExecutor> newActiveList = new ArrayList<>(oldState.activeExecutors.length + wokenUp.size());
                Collections.addAll(newActiveList, oldState.activeExecutors);
                newActiveList.addAll(wokenUp);

                AutoScalingState newState = new AutoScalingState(
                        oldState.activeChildrenCount + wokenUp.size(),
                        startIndex + wokenUp.size(),
                        newActiveList.toArray(new EventExecutor[0]));

                if (state.compareAndSet(oldState, newState)) {
                    return;
                }
                // CAS failed, another thread changed the state. Loop again to retry.
            }
        }