// release is called right after a successful transaction completion. It's job
// is to clear out all the locks, if possible (but if not, no worries,
// they'll expire soon).
func (s *dsTxnState) release(sc *supportContext) {
s.Lock()
defer s.Unlock()
delKeys := make([]string, 0, len(s.toDelete))
for k := range s.toDelete {
delKeys = append(delKeys, k)
}
if err := errors.Filter(sc.mc.DeleteMulti(delKeys), memcache.ErrCacheMiss); err != nil {
(log.Fields{log.ErrorKey: err}).Warningf(
sc.c, "dscache: txn.release: memcache.DeleteMulti")
}
}
func (s *supportContext) mutation(keys []*ds.Key, f func() error) error {
lockItems, lockKeys := s.mkAllLockItems(keys)
if lockItems == nil {
return f()
}
if err := s.mc.SetMulti(lockItems); err != nil {
// this is a hard failure. No mutation can occur if we're unable to set
// locks out. See "DANGER ZONE" in the docs.
(log.Fields{log.ErrorKey: err}).Errorf(
s.c, "dscache: HARD FAILURE: supportContext.mutation(): mc.SetMulti")
return err
}
err := f()
if err == nil {
if err := errors.Filter(s.mc.DeleteMulti(lockKeys), memcache.ErrCacheMiss); err != nil {
(log.Fields{log.ErrorKey: err}).Warningf(
s.c, "dscache: mc.DeleteMulti")
}
}
return err
}
func (d *dsCache) GetMulti(keys []*ds.Key, metas ds.MultiMetaGetter, cb ds.GetMultiCB) error {
lockItems, nonce := d.mkRandLockItems(keys, metas)
if len(lockItems) == 0 {
return d.RawInterface.GetMulti(keys, metas, cb)
}
if err := d.mc.AddMulti(lockItems); err != nil {
// Ignore this error. Either we couldn't add them because they exist
// (so, not an issue), or because memcache is having sad times (in which
// case we'll see so in the GetMulti which immediately follows this).
}
if err := errors.Filter(d.mc.GetMulti(lockItems), memcache.ErrCacheMiss); err != nil {
(log.Fields{log.ErrorKey: err}).Warningf(
d.c, "dscache: GetMulti: memcache.GetMulti")
}
p := makeFetchPlan(d.c, d.aid, d.ns, &facts{keys, metas, lockItems, nonce})
if !p.empty() {
// looks like we have something to pull from datastore, and maybe some work
// to save stuff back to memcache.
toCas := []memcache.Item{}
j := 0
err := d.RawInterface.GetMulti(p.toGet, p.toGetMeta, func(pm ds.PropertyMap, err error) error {
i := p.idxMap[j]
toSave := p.toSave[j]
j++
data := []byte(nil)
// true: save entity to memcache
// false: lock entity in memcache forever
shouldSave := true
if err == nil {
p.decoded[i] = pm
if toSave != nil {
data = encodeItemValue(pm)
if len(data) > internalValueSizeLimit {
shouldSave = false
log.Warningf(
d.c, "dscache: encoded entity too big (%d/%d)!",
len(data), internalValueSizeLimit)
}
}
} else {
p.lme.Assign(i, err)
if err != ds.ErrNoSuchEntity {
return nil // aka continue to the next entry
}
}
if toSave != nil {
if shouldSave { // save
mg := metas.GetSingle(i)
expSecs := ds.GetMetaDefault(mg, CacheExpirationMeta, CacheTimeSeconds).(int64)
toSave.SetFlags(uint32(ItemHasData))
toSave.SetExpiration(time.Duration(expSecs) * time.Second)
toSave.SetValue(data)
} else {
// Set a lock with an infinite timeout. No one else should try to
// serialize this item to memcache until something Put/Delete's it.
toSave.SetFlags(uint32(ItemHasLock))
toSave.SetExpiration(0)
toSave.SetValue(nil)
}
toCas = append(toCas, toSave)
}
return nil
})
if err != nil {
return err
}
if len(toCas) > 0 {
// we have entries to save back to memcache.
if err := d.mc.CompareAndSwapMulti(toCas); err != nil {
(log.Fields{log.ErrorKey: err}).Warningf(
d.c, "dscache: GetMulti: memcache.CompareAndSwapMulti")
}
}
}
// finally, run the callback for all of the decoded items and the errors,
// if any.
for i, dec := range p.decoded {
cb(dec, p.lme.GetOne(i))
}
return nil
}
