Vesta发号器源码解析——MachineIdsIdServiceImpl

这个类是一个对IdServiceImpl的扩展，继承了IdServiceImpl，实现了多个Ids的扩展

相关字段

    //记录最后的时间戳
    protected long lastTimestamp = -1;
    //MachineId的映射关系
    protected Map<Long, Long> machineIdMap = new ConcurrentHashMap<Long, Long>();
    //存储的文件
    public static final String STORE_FILE_NAME = "machineIdInfo.store";
    //存储路径
    private String storeFilePath;
    //存储文件
    private File storeFile;
    //锁，可重入锁
    private Lock lock = new ReentrantLock();

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初始化方法

重写父类中的初始化方法

    @Override
    public void init() {
        //如果当前的MachinId的provider不是MachineIdsProvider接口的实现
        if (!(this.machineIdProvider instanceof MachineIdsProvider)) {
            log.error("The machineIdProvider is not a MachineIdsProvider instance so that Vesta Service refuses to start.");
            throw new RuntimeException(
                    "The machineIdProvider is not a MachineIdsProvider instance so that Vesta Service refuses to start.");
        }
        //调用父类先初始化
        super.init();
        //初始化存储文件
        initStoreFile();
        //初始化MachineId
        initMachineIhid();
    }

---

重写Id生成方法

    @Override
    protected void populateId(Id id) {
        //支持修改MachineId的方法调用
        supportChangeMachineId(id);
    }

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支持修改MachineId的方法

    private void supportChangeMachineId(Id id) {
        try {
            //设置machineId
            id.setMachine(this.machineId);
            //id生成器生成id
            idPopulator.populateId(timer, id, idMeta);
            //记录时间戳
            this.lastTimestamp = id.getTime();
        } catch (IllegalStateException e) {
            //发生时钟回拨，记录日志
            log.warn("Clock moved backwards, change MachineId and reset IdPopulator");
            //加锁
            lock.lock();
            try {
                //如果当前MachineID和id中的相同，修改MachineId然后重置Id生成器
                if (id.getMachine() == this.machineId) {
                    changeMachineId();
                    resetIdPopulator();
                }
            } finally {
                //解锁
                lock.unlock();
            }
            //重新调用一次自己
            supportChangeMachineId(id);
        }
    }

---

修改MachineId

    protected void changeMachineId() {
        //将当前的machineId和时间戳放到map里面
        this.machineIdMap.put(this.machineId, this.lastTimestamp);
        //存进文件里
        storeInFile();
        //初始化machineId
        initMachineId();
    }

---

重置生成器

    protected void resetIdPopulator() {
        //确保id生成器是可重置的
        if (idPopulator instanceof ResetPopulator) {
            //然后充值id生成器
            ((ResetPopulator) idPopulator).reset();
        } else {
            try {
                //否则重新初始化一个Id生成器
                IdPopulator newIdPopulator = this.idPopulator.getClass().newInstance();
                this.idPopulator = newIdPopulator;
            } catch (InstantiationException e1) {
                //抛出重置失败
                throw new RuntimeException("Reset IdPopulator <[" + this.idPopulator.getClass().getCanonicalName() + "]> instance error", e1);
            } catch (IllegalAccessException e1) {
                //抛出重置失败
                throw new RuntimeException("Reset IdPopulator <[" + this.idPopulator.getClass().getCanonicalName() + "]> instance error", e1);
            }
        }
    }

---

初始化存储文件

    protected void initStoreFile() {
        //存储文件的位置没初始化
        if (storeFilePath == null || storeFilePath.length() == 0) {
            //存储文件的路径设置好
            //System.getProperty("user.dir")获取程序当前路径
            storeFilePath = System.getProperty("user.dir") + File.separator + STORE_FILE_NAME;
        }
        try {
            //记录日志
            log.info("machineId info store in <[" + storeFilePath + "]>");
            //存储文件初始化
            storeFile = new File(storeFilePath);
            //文件存在，写入
            if (storeFile.exists(){
                //逐行读取，然后初始化到map中
                BufferedReader reader = new BufferedReader(new FileReader(storeFile));
                String line = reader.readLine();
                while (line != null && line.length() > 0) {
                    String[] kvs = line.split(":");
                    if (kvs.length == 2) {
                        this.machineIdMap.put(Long.parseLong(kvs[0]), Long.parseLong(kvs[1]));
                    } else {
                        throw new IllegalArgumentException(storeFile.getAbsolutePath() + " has illegal value <[" + line + "]>");
                    }
                    line = reader.readLine();
                }
                reader.close();
            }
        } catch (FileNotFoundException e) {
        } catch (IOException e) {
        }
    }

---

初始化机器Id

    protected void initMachineId() {
        //起始Id记录
        long startId = this.machineId;
        //新id记录
        long newMachineId = this.machineId;
        while (true) {
            //如果新的machineId已经在map中存在了
            if (this.machineIdMap.containsKey(newMachineId)) {
                //获取新的时间戳
                long timestamp = timer.genTime();
                //如果新machineId的时间戳比获取的小
                if (this.machineIdMap.get(newMachineId) < timestamp) {
                    //使用新的machineID
                    this.machineId = newMachineId;
                    break;
                } else {
                    //否则获取下一个MachineId作为New
                    newMachineId = ((MachineIdsProvider) this.machineIdProvider).getNextMachineId();
                }
                //如果新的和开始的一样，说明没有id了
                if (newMachineId == startId) {
                    throw new RuntimeException("No machineId is available");
                }
                //校验id是否合法，然后重新循环
                validateMachineId(newMachineId);
            } else {
                //如果不包含直接设置为新的
                //此处通常是上一轮循环到id校验合法，然后回来进入这里退出循环
                this.machineId = newMachineId;
                break;
            }
        }
        //记录日志
        log.warn("MachineId: {}", this.machineId);
    }

---

存储进文件的方法

    protected void storeInFile() {
        //初始化Writer
        Writer writer = null;
        try {
            //初始化文件写入，append参数为false，非追加模式
            writer = new FileWriter(storeFile, false);
            //循环，将map写入文件中
            for (Map.Entry<Long, Long> entry : this.machineIdMap.entrySet()) {
                writer.write(entry.getKey() + ":" + entry.getValue() + "\n");
            }
        } catch (IOException e) {
            //写入异常，记录日志
            log.error("Write machineId info to File<[" + storeFile.getAbsolutePath() + "]> error");
            throw new RuntimeException("Write machineId info to File<[" + storeFile.getAbsolutePath() + "]> error");
        } finally {
            //关闭IO
            if (writer != null) {
                try {
                    writer.close();
                } catch (IOException e) {
                }
            }
        }
    }

---

设置存储文件的路径

    //设置存储文件的位置
    public void setStoreFilePath(String storeFilePath) {
        this.storeFilePath = storeFilePath;
    }