73 lines
1.6 KiB
Go
73 lines
1.6 KiB
Go
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package dao
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import (
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"context"
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"fmt"
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"go-common/library/cache/memcache"
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"go-common/library/log"
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"go-common/library/stat/prom"
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)
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func (d *Dao) Lock(c context.Context, key string, val string) (err error) {
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if val == "" {
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return
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}
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conn := d.mc.Get(c)
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defer conn.Close()
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obj := &struct {
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Value string
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}{
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Value: val,
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}
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item := &memcache.Item{Key: key, Object: obj, Expiration: d.cacheTTL.LockTTL, Flags: memcache.FlagJSON}
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if err = conn.Add(item); err != nil {
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prom.BusinessErrCount.Incr("mc:Lock")
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log.Errorv(c, log.KV("Lock", fmt.Sprintf("%+v", err)), log.KV("key", key))
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return
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}
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return
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}
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// no thread-safe, but it's works.
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// bad case of unlocking：
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// 1, process-a gets lock
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// 2, lock expires
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// 3, process-b gets lock
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// 4, process-a releases lock
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func (d *Dao) Unlock(c context.Context, key string, val string) (err error) {
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conn := d.mc.Get(c)
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defer conn.Close()
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reply, err := conn.Get(key)
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if err != nil {
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if err == memcache.ErrNotFound {
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err = nil
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return
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}
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prom.BusinessErrCount.Incr("mc:Unlock")
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log.Errorv(c, log.KV("Unlock", fmt.Sprintf("%+v", err)), log.KV("key", key))
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return
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}
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res := &struct {
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Value string
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}{}
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err = conn.Scan(reply, &res)
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if err != nil {
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prom.BusinessErrCount.Incr("mc:Unlock")
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log.Errorv(c, log.KV("Unlock", fmt.Sprintf("%+v", err)), log.KV("key", key))
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return
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}
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if res.Value != val {
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return nil
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}
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if err = conn.Delete(key); err != nil {
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if err == memcache.ErrNotFound {
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err = nil
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return
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}
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prom.BusinessErrCount.Incr("mc:Unlock")
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log.Errorv(c, log.KV("Unlock", fmt.Sprintf("%+v", err)), log.KV("key", key))
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return
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}
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return
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}
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