架构师训练营 -week05- 作业 1

public class ExecutorRouteConsistentHash {
    private static int VIRTUAL_NODE_NUM = 100;
    /**     * get hash code on 2^32 ring (md5散列的方式计算hash值)     * @param key     * @return     */    private static long hash(String key) {
        // md5 byte        MessageDigest md5;        try {            md5 = MessageDigest.getInstance("MD5");        } catch (NoSuchAlgorithmException e) {            throw new RuntimeException("MD5 not supported", e);        }        md5.reset();        byte[] keyBytes = null;        try {            keyBytes = key.getBytes("UTF-8");        } catch (UnsupportedEncodingException e) {            throw new RuntimeException("Unknown string :" + key, e);        }
        md5.update(keyBytes);        byte[] digest = md5.digest();
        // hash code, Truncate to 32-bits        long hashCode = ((long) (digest[3] & 0xFF) << 24)                | ((long) (digest[2] & 0xFF) << 16)                | ((long) (digest[1] & 0xFF) << 8)                | (digest[0] & 0xFF);
        long truncateHashCode = hashCode & 0xffffffffL;        return truncateHashCode;    }
    public String hashJob(int jobId, List<String> addressList) {
        // ------A1------A2-------A3------        // -----------J1------------------        TreeMap<Long, String> addressRing = new TreeMap<Long, String>();        for (String address : addressList) {            for (int i = 0; i < VIRTUAL_NODE_NUM; i++) {                long addressHash = hash("SHARD-" + address + "-NODE-" + i);                addressRing.put(addressHash, address);            }        }
        long jobHash = hash(String.valueOf(jobId));        SortedMap<Long, String> lastRing = addressRing.tailMap(jobHash);        if (!lastRing.isEmpty()) {            return lastRing.get(lastRing.firstKey());        }        return addressRing.firstEntry().getValue();    }
    @Override    public ReturnT<String> route(TriggerParam triggerParam, List<String> addressList) {        String address = hashJob(triggerParam.getJobId(), addressList);        return new ReturnT<String>(address);    }
}