// Increment increments the named counter.
func Increment(c context.Context, valName string) error {
// Get counter config.
shardsTotal := dsu.WrapInt{}
dsu.McacheGet(c, mcKeyShardsTotal(valName), &shardsTotal)
if shardsTotal.I < 1 {
ckey := datastore.NewKey(c, dsKindNumShards, mcKeyShardsTotal(valName), 0, nil)
errTx := datastore.RunInTransaction(c,
func(c context.Context) error {
err := datastore.Get(c, ckey, &shardsTotal)
if err == datastore.ErrNoSuchEntity {
shardsTotal.I = defaultNumShards
_, err = datastore.Put(c, ckey, &shardsTotal)
}
return err
}, nil)
if errTx != nil {
return errTx
}
dsu.McacheSet(c, mcKeyShardsTotal(valName), dsu.WrapInt{shardsTotal.I})
}
// pick random counter and increment it
errTx := datastore.RunInTransaction(c,
func(c context.Context) error {
shardId := rand.Intn(shardsTotal.I)
dsKey := datastore.NewKey(c, dsKindShard, keySingleShard(valName, shardId), 0, nil)
var sd WrapShardData
err := datastore.Get(c, dsKey, &sd)
// A missing entity and a present entity will both work.
if err != nil && err != datastore.ErrNoSuchEntity {
return err
}
sd.Name = valName
sd.ShardId = shardId
sd.I++
_, err = datastore.Put(c, dsKey, &sd)
if ll > 2 {
aelog.Infof(c, "ds put %v %v", dsKey, sd)
}
return err
}, nil)
if errTx != nil {
return errTx
}
memcache.Increment(c, mcKey(valName), 1, 0)
// collect number of updates
// per valName per instance in memory
// for every interval of 10 minutes
//
// a batch job checks if the number of shards should be increased or decreased
// and truncates this map
updateSamplingFrequency[valName+util.TimeMarker()[:len("2006-01-02 15:0")]] += 1
return nil
}
// AdjustShards increases the number of shards for the named counter to n.
// It will never decrease the number of shards.
func AdjustShards(c context.Context, valName string, n int) error {
ckey := datastore.NewKey(c, dsKindNumShards, valName, 0, nil)
return datastore.RunInTransaction(c, func(c context.Context) error {
shardsTotal := dsu.WrapInt{}
mod := false
err := datastore.Get(c, ckey, &shardsTotal)
if err == datastore.ErrNoSuchEntity {
shardsTotal.I = n
mod = true
} else if err != nil {
return err
}
if shardsTotal.I < n {
shardsTotal.I = n
mod = true
}
if mod {
_, err = datastore.Put(c, ckey, &shardsTotal)
}
return err
}, nil)
}
// AdjustShards increases the number of shards for the named counter to n.
// It will never decrease the number of shards.
func AdjustShards(c appengine.Context, valName string, n int) error {
ckey := datastore.NewKey(c, dsKindNumShards, valName, 0, nil)
return datastore.RunInTransaction(c, func(c appengine.Context) error {
wNumShards := dsu.WrapInt{}
mod := false
err := datastore.Get(c, ckey, &wNumShards)
if err == datastore.ErrNoSuchEntity {
wNumShards.I = defaultNumShards
mod = true
} else if err != nil {
return err
}
if wNumShards.I < n {
wNumShards.I = n
mod = true
}
if mod {
_, err = datastore.Put(c, ckey, &wNumShards)
}
return err
}, nil)
}