Redis在集羣環境中生成唯一ID

概述

設計目標：每秒最大生成10萬個ID，ID單調遞增且唯一。Reidis可以不需要持久化ID。
要求:集羣時鐘不能倒退。
總體思路：集羣中每個節點預生成生成ID；然後與redis的已經存在的ID做比較。如果大於，則取節點生成的ID；小於的話，取Redis中最大ID自增。

Java代碼

import org.apache.commons.lang3.RandomStringUtils;
import org.apache.commons.lang3.StringUtils;
import org.apache.commons.lang3.time.FastDateFormat;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import static com.google.common.base.Preconditions.checkArgument;
/**
 * 生成遞增的唯一序列號, 可以用來生成訂單號,例如216081817202494579
 * <p/>
 * 生成規則:
 * 業務類型 + redis中最大的序列號
 * <p/>
 * 約定:
 * redis中最大的序列號長度爲17,包括{6位日期 + 6位時間 + 3位毫秒數 + 2位隨機}
 * <p/>
 * 建議:
 * 爲了容錯和服務降級, SeqGenerator生成失敗時最好採用UUID替換
 * <p/>
 * Created by juemingzi on 16/8/19.
 */
public class SeqGenerator {
    private static final Logger logger = LoggerFactory.getLogger(SeqGenerator.class);
    private static final Path filePath = Paths.get(Thread.currentThread().getContextClassLoader().getResource("lua/get_next_seq.lua").getPath());
    //線程安全
    private static final FastDateFormat seqDateFormat = FastDateFormat.getInstance("yyMMddHHmmssSSS");
    private static final RedisExtraService redisExtraService = SpringContext.getBean(RedisExtraService.class);
    private final byte[] keyName;
    private final byte[] incrby;
    private byte[] sha1;
    public SeqGenerator(String keyName) throws IOException {
        this(keyName, 1);
    }
    /**
     * @param keyName
     * @param incrby
     */
    public SeqGenerator(String keyName, int incrby) throws IOException {
        checkArgument(keyName != null && incrby > 0);
        this.keyName = keyName.getBytes();
        this.incrby = Integer.toString(incrby).getBytes();
        init();
    }
    private void init() throws IOException {
        byte[] script;
        try {
            script = Files.readAllBytes(filePath);
        } catch (IOException e) {
            logger.error("讀取文件出錯, path: {}", filePath);
            throw e;
        }
        sha1 = redisExtraService.scriptLoad(script);
    }
    public String getNextSeq(String bizType) {
        checkArgument(StringUtils.isNotBlank(bizType));
        return bizType + getMaxSeq();
    }
    private String generateSeq() {
        String seqDate = seqDateFormat.format(System.currentTimeMillis());
        String candidateSeq = new StringBuilder(17).append(seqDate).append(RandomStringUtils.randomNumeric(2)).toString();
        return candidateSeq;
    }
    /**
     * 通過redis生成17位的序列號,lua腳本保證序列號的唯一性
     *
     * @return
     */
    public String getMaxSeq() {
        String maxSeq = new String((byte[]) redisExtraService.evalsha(sha1, 3, keyName, incrby, generateSeq().getBytes()));
        return maxSeq;
    }
}

lua腳本

--
-- 獲取最大的序列號,樣例爲16081817202494579
--
-- Created by IntelliJ IDEA.
-- User: juemingzi
-- Date: 16/8/18
-- Time: 17:22
local function get_max_seq()
    local key = tostring(KEYS[1])
    local incr_amoutt = tonumber(KEYS[2])
    local seq = tostring(KEYS[3])
    local month_in_seconds = 24 * 60 * 60 * 30
    if (1 == redis.call(\'setnx\', key, seq))
    then
        redis.call(\'expire\', key, month_in_seconds)
        return seq
    else
        local prev_seq = redis.call(\'get\', key)
        if (prev_seq < seq)
        then
            redis.call(\'set\', key, seq)
            return seq
        else
        --[[
            不能直接返回redis.call(\'incr\', key),因爲返回的是number浮點數類型,會出現不精確情況。
            注意: 類似"16081817202494579"數字大小已經快超時lua和reids最大數值,請謹慎的增加seq的位數
        --]]
            redis.call(\'incrby\', key, incr_amoutt)
            return redis.call(\'get\', key)
        end
    end
end
return get_max_seq()

測試代碼

public class SeqGeneratorTest extends BaseTest {
    @Test
    public void testGetNextSeq() throws Exception {
        final SeqGenerator seqGenerater = new SeqGenerator("orderId");
        String orderId = seqGenerater.getNextSeq(Integer.toString(WaitingOrder.KIND_TAKE_OUT));
        assertNotNull(orderId);
        System.out.println("orderId is: " + orderId);
    }
    @Test
    public void testGetNextSeqWithMultiThread() throws Exception {
        int cpus = Runtime.getRuntime().availableProcessors();
        CountDownLatch begin = new CountDownLatch(1);
        CountDownLatch end = new CountDownLatch(cpus);
        final Set<String> seqSet = new ConcurrentSkipListSet<>();
        ExecutorService executorService = Executors.newFixedThreadPool(cpus);
        final SeqGenerator seqGenerater = new SeqGenerator("orderId");
        for (int i = 0; i < cpus; i++) {
            executorService.execute(new Worker(seqGenerater, seqSet, begin, end));
        }
        begin.countDown();
        end.await();
        assertEquals(seqSet.size(), cpus * 10000);
        System.out.println("finish!");
    }
    private static class Worker implements Runnable {
        private final CountDownLatch begin;
        private final CountDownLatch end;
        private final Set<String> seqSet;
        private final SeqGenerator seqGenerator;
        public Worker(SeqGenerator seqGenerator, Set<String> seqSet, CountDownLatch begin, CountDownLatch end) {
            this.seqGenerator = seqGenerator;
            this.seqSet = seqSet;
            this.begin = begin;
            this.end = end;
        }
        @Override
        public void run() {
            try {
                begin.await();
                for (int i = 0; i < 10000; i++) {
                    String seq = seqGenerator.getNextSeq("2");
                    if (!seqSet.add(seq)) {
                        System.out.println(seq);
                        fail();
                    }
                }
                System.out.println("end");
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                end.countDown();
            }
        }
    }
}