聊聊PowerJob的DesignateServer

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本文主要研究一下PowerJob的DesignateServer

DesignateServer

tech/powerjob/server/remote/server/redirector/DesignateServer.java

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface DesignateServer {

    /**
     * 转发请求需要 AppInfo 下的 currentServer 信息，因此必须要有 appId 作为入参，该字段指定了 appId 字段的参数名称，默认为 appId
     * @return appId 参数名称
     */
    String appIdParameterName() default "appId";
}

DesignateServer注解定义了appIdParameterName属性，默认是appId

DesignateServerAspect

tech/powerjob/server/remote/server/redirector/DesignateServerAspect.java

@Slf4j
@Aspect
@Component
@Order(0)
@RequiredArgsConstructor
public class DesignateServerAspect {

    private final TransportService transportService;
    private final AppInfoRepository appInfoRepository;

    private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper();

    @Around(value = "@annotation(designateServer))")
    public Object execute(ProceedingJoinPoint point, DesignateServer designateServer) throws Throwable {

        // 参数
        Object[] args = point.getArgs();
        // 方法名
        String methodName = point.getSignature().getName();
        // 类名
        String className = point.getSignature().getDeclaringTypeName();
        Signature signature = point.getSignature();
        // 方法签名
        MethodSignature methodSignature = (MethodSignature) signature;
        String[] parameterNames = methodSignature.getParameterNames();
        String[] parameterTypes = Arrays.stream(methodSignature.getParameterTypes()).map(Class::getName).toArray(String[]::new);

        Long appId = null;
        for (int i = 0; i < parameterNames.length; i++) {
            if (StringUtils.equals(parameterNames[i], designateServer.appIdParameterName())) {
                appId = Long.parseLong(String.valueOf(args[i]));
                break;
            }
        }

        if (appId == null) {
            throw new PowerJobException("can't find appId in params for:" + signature);
        }

        // 获取执行机器
        AppInfoDO appInfo = appInfoRepository.findById(appId).orElseThrow(() -> new PowerJobException("can't find app info"));
        String targetServer = appInfo.getCurrentServer();

        // 目标IP为空，本地执行
        if (StringUtils.isEmpty(targetServer)) {
            return point.proceed();
        }

        // 目标IP与本地符合则本地执行
        if (Objects.equals(targetServer, transportService.defaultProtocol().getAddress())) {
            return point.proceed();
        }

        log.info("[DesignateServerAspect] the method[{}] should execute in server[{}], so this request will be redirect to remote server!", signature.toShortString(), targetServer);
        // 转发请求，远程执行后返回结果
        RemoteProcessReq remoteProcessReq = new RemoteProcessReq()
                .setClassName(className)
                .setMethodName(methodName)
                .setParameterTypes(parameterTypes)
                .setArgs(args);

        final URL friendUrl = ServerURLFactory.process2Friend(targetServer);

        CompletionStage<AskResponse> askCS = transportService.ask(Protocol.HTTP.name(), friendUrl, remoteProcessReq, AskResponse.class);
        AskResponse askResponse = askCS.toCompletableFuture().get(RemoteConstant.DEFAULT_TIMEOUT_MS, TimeUnit.MILLISECONDS);

        if (!askResponse.isSuccess()) {
            throw new PowerJobException("remote process failed: " + askResponse.getMessage());
        }

        // 考虑范型情况
        Method method = methodSignature.getMethod();
        JavaType returnType = getMethodReturnJavaType(method);

        return OBJECT_MAPPER.readValue(askResponse.getData(), returnType);
    }

    //......
}    

DesignateServerAspect拦截了@DesignateServer注解，它先解析方法参数名，取出参数名与@DesignateServer的appIdParameterName一致的参数值，再通过appInfoRepository.findById找到AppInfoDO，获取appInfo.getCurrentServer()；若currentServer就是本机则执行point.proceed()，否则构建RemoteProcessReq，通过transportService.ask转发请求

示例

tech/powerjob/server/core/instance/InstanceLogService.java

    /**
     * 获取日志的下载链接
     * @param appId AOP 专用
     * @param instanceId 任务实例 ID
     * @return 下载链接
     */
    @DesignateServer
    public String fetchDownloadUrl(Long appId, Long instanceId) {
        String url = "http://" + NetUtils.getLocalHost() + ":" + port + "/instance/downloadLog?instanceId=" + instanceId;
        log.info("[InstanceLog-{}] downloadURL for appId[{}]: {}", instanceId, appId, url);
        return url;
    }

fetchDownloadUrl指定了@DesignateServer注解，会根据appId的值限定在指定server执行

小结

PowerJob的DesignateServer注解定义了appIdParameterName属性，默认是appId；DesignateServerAspect拦截了@DesignateServer注解，它判断currentServer就是本机则执行point.proceed()，否则构建RemoteProcessReq，通过transportService.ask转发请求到指定server执行。