41 lines
1012 B
Go
41 lines
1012 B
Go
package stocklock
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import (
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"context"
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"errors"
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"github.com/redis/go-redis/v9"
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)
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var (
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ErrSoldOut = errors.New("库存不足")
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ErrDuplicate = errors.New("每人限购一件，已经抢过了")
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)
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// 原子地：检查是否已购买 → 检查库存 → 扣库存 → 记录用户
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var reserveScript = redis.NewScript(`
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if redis.call("SISMEMBER", KEYS[2], ARGV[1]) == 1 then
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return -2
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end
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local left = tonumber(redis.call("GET", KEYS[1]) or "0")
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if left <= 0 then
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return -1
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end
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redis.call("DECR", KEYS[1])
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redis.call("SADD", KEYS[2], ARGV[1])
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return left - 1`)
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// Reserve 预扣库存。成功后应把订单消息发到 MQ，由消费者异步落库。
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func Reserve(ctx context.Context, rdb *redis.Client, sku, userID string) (left int, err error) {
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n, err := reserveScript.Run(ctx, rdb, []string{"stock:" + sku, "stock:" + sku + ":buyers"}, userID).Int()
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switch {
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case err != nil:
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return 0, err
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case n == -1:
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return 0, ErrSoldOut
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case n == -2:
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return 0, ErrDuplicate
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}
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return n, nil
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}
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