Talk nacos config of doPollingConfig

sequence

In this paper, we look nacos config of doPollingConfig

ConfigController

nacos-1.1.3/config/src/main/java/com/alibaba/nacos/config/server/controller/ConfigController.java

@Controller
@RequestMapping(Constants.CONFIG_CONTROLLER_PATH)
public class ConfigController {

    private static final Logger log = LoggerFactory.getLogger(ConfigController.class);

    private static final String NAMESPACE_PUBLIC_KEY = "public";

    public static final String EXPORT_CONFIG_FILE_NAME = "nacos_config_export_";

    public static final String EXPORT_CONFIG_FILE_NAME_EXT = ".zip";

    public static final String EXPORT_CONFIG_FILE_NAME_DATE_FORMAT = "yyyy-MM-dd HH:mm:ss";

    private final transient ConfigServletInner inner;

    private final transient PersistService persistService;

    private final transient ConfigSubService configSubService;

    //......

    @RequestMapping(value = "/listener", method = RequestMethod.POST)
    public void listener(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
        request.setAttribute("org.apache.catalina.ASYNC_SUPPORTED", true);
        String probeModify = request.getParameter("Listening-Configs");
        if (StringUtils.isBlank(probeModify)) {
            throw new IllegalArgumentException("invalid probeModify");
        }

        probeModify = URLDecoder.decode(probeModify, Constants.ENCODE);

        Map<String, String> clientMd5Map;
        try {
            clientMd5Map = MD5Util.getClientMd5Map(probeModify);
        } catch (Throwable e) {
            throw new IllegalArgumentException("invalid probeModify");
        }

        // do long-polling
        inner.doPollingConfig(request, response, clientMd5Map, probeModify.length());
    }

    //......
}
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• The listener method ConfigController Listening-Configs reads the parameters from the request, and then decode, calculated clientMd5Map, performed last inner.doPollingConfig

ConfigServletInner

nacos-1.1.3/config/src/main/java/com/alibaba/nacos/config/server/controller/ConfigServletInner.java

@Service
public class ConfigServletInner {

    @Autowired
    private LongPollingService longPollingService;

    @Autowired
    private PersistService persistService;

    private static final int TRY_GET_LOCK_TIMES = 9;

    private static final int START_LONGPOLLING_VERSION_NUM = 204;

    /**
     * 轮询接口
     */
    public String doPollingConfig(HttpServletRequest request, HttpServletResponse response,
                                  Map<String, String> clientMd5Map, int probeRequestSize)
        throws IOException, ServletException {

        // 长轮询
        if (LongPollingService.isSupportLongPolling(request)) {
            longPollingService.addLongPollingClient(request, response, clientMd5Map, probeRequestSize);
            return HttpServletResponse.SC_OK + "";
        }

        // else 兼容短轮询逻辑
        List<String> changedGroups = MD5Util.compareMd5(request, response, clientMd5Map);

        // 兼容短轮询result
        String oldResult = MD5Util.compareMd5OldResult(changedGroups);
        String newResult = MD5Util.compareMd5ResultString(changedGroups);

        String version = request.getHeader(Constants.CLIENT_VERSION_HEADER);
        if (version == null) {
            version = "2.0.0";
        }
        int versionNum = Protocol.getVersionNumber(version);

        /**
         * 2.0.4版本以前, 返回值放入header中
         */
        if (versionNum < START_LONGPOLLING_VERSION_NUM) {
            response.addHeader(Constants.PROBE_MODIFY_RESPONSE, oldResult);
            response.addHeader(Constants.PROBE_MODIFY_RESPONSE_NEW, newResult);
        } else {
            request.setAttribute("content", newResult);
        }

        // 禁用缓存
        response.setHeader("Pragma", "no-cache");
        response.setDateHeader("Expires", 0);
        response.setHeader("Cache-Control", "no-cache,no-store");
        response.setStatus(HttpServletResponse.SC_OK);
        return HttpServletResponse.SC_OK + "";
    }

    //......
}
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• ConfigServletInner of doPollingConfig method first determine whether the request to support long polling, if support is performed longPollingService.addLongPollingClient; do not support it will newResult into the content, and then return

LongPollingService

nacos-1.1.3/config/src/main/java/com/alibaba/nacos/config/server/service/LongPollingService.java

@Service
public class LongPollingService extends AbstractEventListener {

    private static final int FIXED_POLLING_INTERVAL_MS = 10000;

    private static final int SAMPLE_PERIOD = 100;

    private static final int SAMPLE_TIMES = 3;

    private static final String TRUE_STR = "true";

    private Map<String, Long> retainIps = new ConcurrentHashMap<String, Long>();

    private static boolean isFixedPolling() {
        return SwitchService.getSwitchBoolean(SwitchService.FIXED_POLLING, false);
    }

    //......

    static public boolean isSupportLongPolling(HttpServletRequest req) {
        return null != req.getHeader(LONG_POLLING_HEADER);
    }

    public void addLongPollingClient(HttpServletRequest req, HttpServletResponse rsp, Map<String, String> clientMd5Map,
                                     int probeRequestSize) {

        String str = req.getHeader(LongPollingService.LONG_POLLING_HEADER);
        String noHangUpFlag = req.getHeader(LongPollingService.LONG_POLLING_NO_HANG_UP_HEADER);
        String appName = req.getHeader(RequestUtil.CLIENT_APPNAME_HEADER);
        String tag = req.getHeader("Vipserver-Tag");
        int delayTime = SwitchService.getSwitchInteger(SwitchService.FIXED_DELAY_TIME, 500);
        /**
         * 提前500ms返回响应，为避免客户端超时 @qiaoyi.dingqy 2013.10.22改动  add delay time for LoadBalance
         */
        long timeout = Math.max(10000, Long.parseLong(str) - delayTime);
        if (isFixedPolling()) {
            timeout = Math.max(10000, getFixedPollingInterval());
            // do nothing but set fix polling timeout
        } else {
            long start = System.currentTimeMillis();
            List<String> changedGroups = MD5Util.compareMd5(req, rsp, clientMd5Map);
            if (changedGroups.size() > 0) {
                generateResponse(req, rsp, changedGroups);
                LogUtil.clientLog.info("{}|{}|{}|{}|{}|{}|{}",
                    System.currentTimeMillis() - start, "instant", RequestUtil.getRemoteIp(req), "polling",
                    clientMd5Map.size(), probeRequestSize, changedGroups.size());
                return;
            } else if (noHangUpFlag != null && noHangUpFlag.equalsIgnoreCase(TRUE_STR)) {
                LogUtil.clientLog.info("{}|{}|{}|{}|{}|{}|{}", System.currentTimeMillis() - start, "nohangup",
                    RequestUtil.getRemoteIp(req), "polling", clientMd5Map.size(), probeRequestSize,
                    changedGroups.size());
                return;
            }
        }
        String ip = RequestUtil.getRemoteIp(req);
        // 一定要由HTTP线程调用，否则离开后容器会立即发送响应
        final AsyncContext asyncContext = req.startAsync();
        // AsyncContext.setTimeout()的超时时间不准，所以只能自己控制
        asyncContext.setTimeout(0L);

        scheduler.execute(
            new ClientLongPolling(asyncContext, clientMd5Map, ip, probeRequestSize, timeout, appName, tag));
    }

    //......
}
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• LongPollingService of isSupportLongPolling is achieved by determining whether the request has LONG_POLLING_HEADER the header; addLongPollingClient method is to create ClientLongPolling, and then submitted to the scheduler execution

ClientLongPolling

nacos-1.1.3/config/src/main/java/com/alibaba/nacos/config/server/service/LongPollingService.java

@Service
public class LongPollingService extends AbstractEventListener {

	//......

    class ClientLongPolling implements Runnable {

        @Override
        public void run() {
            asyncTimeoutFuture = scheduler.schedule(new Runnable() {
                @Override
                public void run() {
                    try {
                        getRetainIps().put(ClientLongPolling.this.ip, System.currentTimeMillis());
                        /**
                         * 删除订阅关系
                         */
                        allSubs.remove(ClientLongPolling.this);

                        if (isFixedPolling()) {
                            LogUtil.clientLog.info("{}|{}|{}|{}|{}|{}",
                                (System.currentTimeMillis() - createTime),
                                "fix", RequestUtil.getRemoteIp((HttpServletRequest)asyncContext.getRequest()),
                                "polling",
                                clientMd5Map.size(), probeRequestSize);
                            List<String> changedGroups = MD5Util.compareMd5(
                                (HttpServletRequest)asyncContext.getRequest(),
                                (HttpServletResponse)asyncContext.getResponse(), clientMd5Map);
                            if (changedGroups.size() > 0) {
                                sendResponse(changedGroups);
                            } else {
                                sendResponse(null);
                            }
                        } else {
                            LogUtil.clientLog.info("{}|{}|{}|{}|{}|{}",
                                (System.currentTimeMillis() - createTime),
                                "timeout", RequestUtil.getRemoteIp((HttpServletRequest)asyncContext.getRequest()),
                                "polling",
                                clientMd5Map.size(), probeRequestSize);
                            sendResponse(null);
                        }
                    } catch (Throwable t) {
                        LogUtil.defaultLog.error("long polling error:" + t.getMessage(), t.getCause());
                    }

                }

            }, timeoutTime, TimeUnit.MILLISECONDS);

            allSubs.add(this);
        }

        void sendResponse(List<String> changedGroups) {
            /**
             *  取消超时任务
             */
            if (null != asyncTimeoutFuture) {
                asyncTimeoutFuture.cancel(false);
            }
            generateResponse(changedGroups);
        }

        void generateResponse(List<String> changedGroups) {
            if (null == changedGroups) {
                /**
                 * 告诉容器发送HTTP响应
                 */
                asyncContext.complete();
                return;
            }

            HttpServletResponse response = (HttpServletResponse)asyncContext.getResponse();

            try {
                String respString = MD5Util.compareMd5ResultString(changedGroups);

                // 禁用缓存
                response.setHeader("Pragma", "no-cache");
                response.setDateHeader("Expires", 0);
                response.setHeader("Cache-Control", "no-cache,no-store");
                response.setStatus(HttpServletResponse.SC_OK);
                response.getWriter().println(respString);
                asyncContext.complete();
            } catch (Exception se) {
                pullLog.error(se.toString(), se);
                asyncContext.complete();
            }
        }

        ClientLongPolling(AsyncContext ac, Map<String, String> clientMd5Map, String ip, int probeRequestSize,
                          long timeoutTime, String appName, String tag) {
            this.asyncContext = ac;
            this.clientMd5Map = clientMd5Map;
            this.probeRequestSize = probeRequestSize;
            this.createTime = System.currentTimeMillis();
            this.ip = ip;
            this.timeoutTime = timeoutTime;
            this.appName = appName;
            this.tag = tag;
        }

        // =================

        final AsyncContext asyncContext;
        final Map<String, String> clientMd5Map;
        final long createTime;
        final String ip;
        final String appName;
        final String tag;
        final int probeRequestSize;
        final long timeoutTime;

        Future<?> asyncTimeoutFuture;
    }

	//......
}
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• ClientLongPolling implement the Runnable interface, its run method first register a timeout task to get asyncTimeoutFuture, and then perform allSubs.add (this)
• The first task timeout to retainIps record ClientLongPolling.this.ip and the current time stamp, and then remove yourself from allSubs, after non-fixedPolling for direct execution sendResponse (null), otherwise they will be calculated by changedGroups under MD5Util.compareMd5, if not changedGroups empty the execution sendResponse (changedGroups), otherwise perform sendResponse (null)
• sendResponse method first cancel asyncTimeoutFuture, and then perform generateResponse (changedGroups), the method for changedGroups of direct asyncContext.complete null (), otherwise MD5Util.compareMd5ResultString (changedGroups) get respString, then wrote in response

summary

ConfigController the request from listener method reads the Listening-Configs parameters, and then decode, calculated clientMd5Map, the final implementation inner.doPollingConfig; ConfigServletInner doPollingConfig the method first determines whether the request to support long polling, it is supported longPollingService.addLongPollingClient executed; do not support it newResult content will be placed, and then return

doc

• ConfigController