Redis從入門到放棄系列(十) Cluster

Redis從入門到放棄系列(十) Cluster

本文例子基於：5.0.4

Redis Cluster集羣高可用方案,去中心化,最基本三主多從,主從切換相似Sentinel,關於Sentinel內容能夠查看編者另一篇【Redis從入門到放棄系列(九) Sentinel】.

在Redis Cluster中,只存在index爲0的數據庫,並且其實Redis做爲單線程,若是在同一個實例上建立多個庫的話,也是須要上下文切換的.

slot

因爲Redis Cluster是採用16384個slot來劃分數據的,也就是說你當前插入的數據會存在不一樣的節點上,簡而言之不支持比較複雜的多建操做(能夠對key打上hash tags來解決).

咱們說Cluster是按照16384個slot來劃分數據的,那麼是如何來肯定一個key落在那個節點上呢?

//計算slot
HASH_SLOT = CRC16(key) mod 16384
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每一個節點會擁有一部分的slot,經過上述獲取到具體key的slot即知道應該去哪兒找對應的節點啦.但是在網絡中,一切都會有不存穩定因素,網絡抖動.

當在Cluster中存在網絡抖動的時候,當時間過長,有可能產生下線,其實原理跟Sentinel裏面講的很類似,由於都是依賴Gossip協議來實現的.能夠經過如下配置來設置肯定下線的時間.

//節點持續timeout的時間,才認定該節點出現故障,須要進行主從切換,
cluster-node-timeout
//做爲上面timeout的係數來放大時間
cluster-replica-validity-factor
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因爲數據是按照16384個slot去劃分的,那麼當咱們在請求某個key到錯誤的節點,這時候key不在該節點上,Redis會向咱們發送一個錯誤

-MOVED 3999 127.0.0.1:6381
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該消息是提示咱們該key應該是存在127.0.0.1這臺服務器上面的3999slot,這時候就須要咱們的redis客戶端去糾正本地的slot映射表,而後請求對應的地址.

增刪集羣節點

當咱們在增長或者刪除某個節點的時候,其實就只是將slot從某個節點移動到另一個節點.可使用一下命令來完成這一件事

• CLUSTER ADDSLOTS slot1 [slot2] ... [slotN]
• CLUSTER DELSLOTS slot1 [slot2] ... [slotN]
• CLUSTER SETSLOT slot NODE node
• CLUSTER SETSLOT slot MIGRATING node
• CLUSTER SETSLOT slot IMPORTING node 有時候運維須要對redis節點的某些數據作遷移,官方提供了redis-trib工具來完成這件事情。

在遷移的時候,redis節點會存在兩種狀態,一種是MIGRATING和IMPORTING,用於將slot從一個節點遷移到另一個節點.

• 節點狀態設置爲MIGRATING時，將接受與此散列槽有關的全部查詢，但僅當有問題的key存在時才能接受，不然將使用-Ask重定向將查詢轉發到做爲遷移目標的節點。
• 節點狀態設置爲IMPORTING時，節點將接受與此哈希槽有關的全部查詢，但前提是請求前面有ASKING命令。若是客戶端沒有發出ASKING命令，查詢將經過-MOVED重定向錯誤重定向到真正的散列槽全部者

多線程批量獲取/刪除

public class RedisUtils {

	private static final String LOCK_SUCCESS = "OK";
	private static final String SET_IF_NOT_EXIST = "NX";
	private static final String SET_WITH_EXPIRE_TIME = "PX";
	private static final Long RELEASE_SUCCESS = 1L;

	private final ThreadLocal<String> requestId = new ThreadLocal<>();

	private final static ExecutorService executorService = new ThreadPoolExecutor(
			//核心線程數量
			1,
			//最大線程數量
			8,
			//當線程空閒時，保持活躍的時間
			1000,
			//時間單元 ，毫秒級
			TimeUnit.MILLISECONDS,
			//線程任務隊列
			new LinkedBlockingQueue<>(1024),
			//建立線程的工廠
			new RedisTreadFactory("redis-batch"));

	@Autowired
	private JedisCluster jedisCluster;

	public String set(String key, String value) {
		return jedisCluster.set(key, value);
	}

	public String get(String key) {
		return jedisCluster.get(key);
	}

	public Map<String, String> getBatchKey(List<String> keys) {
		Map<Jedis, List<String>> nodeKeyListMap = jedisKeys(keys);
		//結果集
		Map<String, String> resultMap = new HashMap<>();
		CompletionService<Map<String,String>> batchService = new ExecutorCompletionService(executorService);
		nodeKeyListMap.forEach((k,v)->{
			batchService.submit(new BatchGetTask(k,v));
		});
		nodeKeyListMap.forEach((k,v)->{
			try {
				resultMap.putAll(batchService.take().get());
			} catch (InterruptedException | ExecutionException e) {
				e.printStackTrace();
			}
		});
		return resultMap;
	}

	public boolean lock(String lockKey, long expireTime){
		String uuid = UUID.randomUUID().toString();
		requestId.set(uuid);
		String result = jedisCluster.set(lockKey, uuid, SET_IF_NOT_EXIST, SET_WITH_EXPIRE_TIME, expireTime);
		return LOCK_SUCCESS.equals(result);
	}

	public boolean unLock(String lockKey){
		String uuid = requestId.get();
		String script = "if redis.call('get', KEYS[1]) == ARGV[1] then return redis.call('del', KEYS[1]) else return 0 end";
		Object result = jedisCluster.eval(script, Collections.singletonList(lockKey), Collections.singletonList(uuid));
		requestId.remove();
		return RELEASE_SUCCESS.equals(result);
	}

	private Map<Jedis, List<String>> jedisKeys(List<String> keys){
		Map<Jedis, List<String>> nodeKeyListMap = new HashMap<>();
		for (String key : keys) {
			//計算slot
			int slot = JedisClusterCRC16.getSlot(key);
			Jedis jedis = jedisCluster.getConnectionFromSlot(slot);
			if (nodeKeyListMap.containsKey(jedis)) {
				nodeKeyListMap.get(jedis).add(key);
			} else {
				nodeKeyListMap.put(jedis, Arrays.asList(key));
			}
		}
		return nodeKeyListMap;
	}

	public long delBatchKey(List<String> keys){
		Map<Jedis, List<String>> nodeKeyListMap = jedisKeys(keys);
		CompletionService<Long> batchService = new ExecutorCompletionService(executorService);
		nodeKeyListMap.forEach((k,v)->{
			batchService.submit(new BatchDelTask(k,v));
		});
		Long result = 0L;
		for (int i=0;i<nodeKeyListMap.size();i++){
			try {
				result += batchService.take().get();
			} catch (InterruptedException | ExecutionException e) {
				e.printStackTrace();
			}
		}
		return result;
	}

	class BatchGetTask implements Callable<Map<String,String>>{

		private Jedis jedis;

		private List<String> keys;

		private BatchGetTask(Jedis jedis, List<String> keys) {
			this.jedis = jedis;
			this.keys = keys;
		}

		@Override
		public Map<String, String> call() throws Exception {
			Map<String, String> resultMap = new HashMap<>();
			String[] keyArray = keys.toArray(new String[]{});
			try {
				List<String> nodeValueList = jedis.mget(keyArray);
				for (int i = 0; i < keys.size(); i++) {
					resultMap.put(keys.get(i),nodeValueList.get(i));
				}
			}finally {
				jedis.close();
			}
			return resultMap;
		}
	}

	class BatchDelTask implements Callable<Long>{

		private Jedis jedis;

		private List<String> keys;

		private BatchDelTask(Jedis jedis, List<String> keys) {
			this.jedis = jedis;
			this.keys = keys;
		}

		@Override
		public Long call() throws Exception {
			String[] keyArray = keys.toArray(new String[]{});
			try {
				return jedis.del(keyArray);
			}finally {
				jedis.close();
			}
		}
	}

	 static class RedisTreadFactory implements ThreadFactory{

		private final AtomicInteger threadNumber = new AtomicInteger(0);

		private final String namePredix;

		public RedisTreadFactory(String namePredix) {
			this.namePredix = namePredix +"-";
		}

		@Override
		public Thread newThread(Runnable r) {
			Thread t = new Thread( r,namePredix + threadNumber.getAndIncrement());
			if (t.isDaemon())
				t.setDaemon(true);
			if (t.getPriority() != Thread.NORM_PRIORITY)
				t.setPriority(Thread.NORM_PRIORITY);
			return t;
		}
	}
}
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寫在最後

Redis從入門到放棄系列終於完結啦！！！！！！！！！！！

寫博客,真的是很是耗時間,真的,原本星期六日要寫的,然而由於某些問題而沒有寫出來(PS:純粹是由於打遊戲.hhhh),終於在今天痛定思痛,頂着脖子酸的壓力(PS:貼着狗皮膏藥在擼碼),終於完結了.

感謝各位看官那麼辛苦看我碼字,真心感謝.

但願寫的東西對各位看官有啓發.