聊聊PowerJob的ServerController

序

本文主要研究一下PowerJob的ServerController

ServerController

tech/powerjob/server/web/controller/ServerController.java

@RestController
@RequestMapping("/server")
@RequiredArgsConstructor
public class ServerController implements ServerInfoAware {

    private ServerInfo serverInfo;
    private final TransportService transportService;

    private final ServerElectionService serverElectionService;

    private final AppInfoRepository appInfoRepository;

    private final WorkerClusterQueryService workerClusterQueryService;

    @GetMapping("/assert")
    public ResultDTO assertAppName(String appName) {
        Optional appInfoOpt = appInfoRepository.findByAppName(appName);
        return appInfoOpt.map(appInfoDO -> ResultDTO.success(appInfoDO.getId())).
                orElseGet(() -> ResultDTO.failed(String.format("app(%s) is not registered! Please register the app in oms-console first.", appName)));
    }

    @GetMapping("/assertV2")
    public ResultDTO assertAppNameV2(String appName) {
        Optional appInfoOpt = appInfoRepository.findByAppName(appName);
        return appInfoOpt.map(appInfoDO -> {
                    WorkerAppInfo workerAppInfo = new WorkerAppInfo().setAppId(appInfoDO.getId());
                    return ResultDTO.success(workerAppInfo);
                }).
                orElseGet(() -> ResultDTO.failed(String.format("app(%s) is not registered! Please register the app in oms-console first.", appName)));
    }

    @GetMapping("/acquire")
    public ResultDTO acquireServer(ServerDiscoveryRequest request) {
        return ResultDTO.success(serverElectionService.elect(request));
    }

    @GetMapping("/hello")
    public ResultDTO ping(@RequestParam(required = false) boolean debug) {
        JSONObject res = new JSONObject();
        res.put("localHost", NetUtils.getLocalHost());
        res.put("serverInfo", serverInfo);
        res.put("serverTime", CommonUtils.formatTime(System.currentTimeMillis()));
        res.put("serverTimeTs", System.currentTimeMillis());
        res.put("serverTimeZone", TimeZone.getDefault().getDisplayName());
        res.put("appIds", workerClusterQueryService.getAppId2ClusterStatus().keySet());
        if (debug) {
            res.put("appId2ClusterInfo", JSON.parseObject(JSON.toJSONString(workerClusterQueryService.getAppId2ClusterStatus())));
        }

        try {
            res.put("defaultAddress", JSONObject.toJSON(transportService.defaultProtocol()));
        } catch (Exception ignore) {
        }

        return ResultDTO.success(res);
    }

    @Override
    public void setServerInfo(ServerInfo serverInfo) {
        this.serverInfo = serverInfo;
    }
}

ServerController实现了ServerInfoAware接口，它提供了assert、assertV2、acquire、hello接口；其中assert接口用于判断指定的appName是否存在，assertV2返回的是WorkerAppInfo；acquire委托给了serverElectionService.elect(request)；hello接口返回server端的localhost、serverInfo、serverTime等信息

elect

tech/powerjob/server/remote/server/election/ServerElectionService.java

    public String elect(ServerDiscoveryRequest request) {
        if (!accurate()) {
            final String currentServer = request.getCurrentServer();
            // 如果是本机，就不需要查数据库那么复杂的操作了，直接返回成功
            Optional localProtocolInfoOpt = Optional.ofNullable(transportService.allProtocols().get(request.getProtocol()));
            if (localProtocolInfoOpt.isPresent()) {
                if (localProtocolInfoOpt.get().getExternalAddress().equals(currentServer) || localProtocolInfoOpt.get().getAddress().equals(currentServer)) {
                    log.info("[ServerElection] this server[{}] is worker[appId={}]'s current server, skip check", currentServer, request.getAppId());
                    return currentServer;
                }
            }
        }
        return getServer0(request);
    }

    private boolean accurate() {
        return ThreadLocalRandom.current().nextInt(100) < accurateSelectServerPercentage;
    }    

ServerElectionService的elect方法接收ServerDiscoveryRequest，它先判断是否accurate(判断100以内的随机数是否小于accurateSelectServerPercentage，默认50)，是则执行getServer0，否则则先判断ProtocolInfo的address是否是currentServer，是则直接返回，否则还是走getServer0

getServer0

    private String getServer0(ServerDiscoveryRequest discoveryRequest) {

        final Long appId = discoveryRequest.getAppId();
        final String protocol = discoveryRequest.getProtocol();
        Set downServerCache = Sets.newHashSet();

        for (int i = 0; i < RETRY_TIMES; i++) {

            // 无锁获取当前数据库中的Server
            Optional appInfoOpt = appInfoRepository.findById(appId);
            if (!appInfoOpt.isPresent()) {
                throw new PowerJobException(appId + " is not registered!");
            }
            String appName = appInfoOpt.get().getAppName();
            String originServer = appInfoOpt.get().getCurrentServer();
            String activeAddress = activeAddress(originServer, downServerCache, protocol);
            if (StringUtils.isNotEmpty(activeAddress)) {
                return activeAddress;
            }

            // 无可用Server，重新进行Server选举，需要加锁
            String lockName = String.format(SERVER_ELECT_LOCK, appId);
            boolean lockStatus = lockService.tryLock(lockName, 30000);
            if (!lockStatus) {
                try {
                    Thread.sleep(500);
                }catch (Exception ignore) {
                }
                continue;
            }
            try {

                // 可能上一台机器已经完成了Server选举，需要再次判断
                AppInfoDO appInfo = appInfoRepository.findById(appId).orElseThrow(() -> new RuntimeException("impossible, unless we just lost our database."));
                String address = activeAddress(appInfo.getCurrentServer(), downServerCache, protocol);
                if (StringUtils.isNotEmpty(address)) {
                    return address;
                }

                // 篡位，如果本机存在协议，则作为Server调度该 worker
                final ProtocolInfo targetProtocolInfo = transportService.allProtocols().get(protocol);
                if (targetProtocolInfo != null) {
                    // 注意，写入 AppInfoDO#currentServer 的永远是 default 的绑定地址，仅在返回的时候特殊处理为协议地址
                    appInfo.setCurrentServer(transportService.defaultProtocol().getAddress());
                    appInfo.setGmtModified(new Date());

                    appInfoRepository.saveAndFlush(appInfo);
                    log.info("[ServerElection] this server({}) become the new server for app(appId={}).", appInfo.getCurrentServer(), appId);
                    return targetProtocolInfo.getExternalAddress();
                }
            }catch (Exception e) {
                log.error("[ServerElection] write new server to db failed for app {}.", appName, e);
            } finally {
                lockService.unlock(lockName);
            }
        }
        throw new PowerJobException("server elect failed for app " + appId);
    }

getServer0执行一个循环(最大10次)，它先根据appId获取AppInfoDO，然后通过activeAddress判断server是否存活，是则返回，否则重新进行server选举

activeAddress

    private String activeAddress(String serverAddress, Set downServerCache, String protocol) {

        if (downServerCache.contains(serverAddress)) {
            return null;
        }
        if (StringUtils.isEmpty(serverAddress)) {
            return null;
        }

        Ping ping = new Ping();
        ping.setCurrentTime(System.currentTimeMillis());

        URL targetUrl = ServerURLFactory.ping2Friend(serverAddress);
        try {
            AskResponse response = transportService.ask(Protocol.HTTP.name(), targetUrl, ping, AskResponse.class)
                    .toCompletableFuture()
                    .get(PING_TIMEOUT_MS, TimeUnit.MILLISECONDS);
            if (response.isSuccess()) {
                // 检测通过的是远程 server 的暴露地址，需要返回 worker 需要的协议地址
                final JSONObject protocolInfo = JsonUtils.parseObject(response.getData(), JSONObject.class).getJSONObject(protocol);
                if (protocolInfo != null) {
                    downServerCache.remove(serverAddress);
                    ProtocolInfo remoteProtocol = protocolInfo.toJavaObject(ProtocolInfo.class);
                    log.info("[ServerElection] server[{}] is active, it will be the master, final protocol={}", serverAddress, remoteProtocol);
                    // 4.3.3 升级 4.3.4 过程中，未升级的 server 还不存在 externalAddress，需要使用 address 兼容
                    return Optional.ofNullable(remoteProtocol.getExternalAddress()).orElse(remoteProtocol.getAddress());
                } else {
                    log.warn("[ServerElection] server[{}] is active but don't have target protocol", serverAddress);
                }
            }
        } catch (TimeoutException te) {
            log.warn("[ServerElection] server[{}] was down due to ping timeout!", serverAddress);
        } catch (Exception e) {
            log.warn("[ServerElection] server[{}] was down with unknown case!", serverAddress, e);
        }
        downServerCache.add(serverAddress);
        return null;
    }

activeAddress通过transportService.ask请求ping接口，1s超时，若成功则从downServerCache移除，返回remoteProtocol.getAddress()，若失败则将该serverAddress加入downServerCache

小结

ServerController实现了ServerInfoAware接口，它提供了assert、assertV2、acquire、hello接口；其中assert接口用于判断指定的appName是否存在，assertV2返回的是WorkerAppInfo；acquire委托给了serverElectionService.elect(request)；hello接口返回server端的localhost、serverInfo、serverTime等信息。