func (this *Dag) MakeDotGraph(fn string) {
file, err := os.OpenFile(fn, os.O_WRONLY|os.O_CREATE, 0644)
if err != nil {
panic(err)
}
defer file.Close()
sb := str.NewStringBuilder()
sb.WriteString("digraph depgraph {\n\trankdir=LR;\n")
for _, node := range this.nodes {
node.dotGraph(sb)
}
sb.WriteString("}\n")
file.WriteString(sb.String())
}
// 184 ns/op
func BenchmarkStringBuilderConcat(b *testing.B) {
const (
s1 = "SELECT shardId FROM "
s2 = " WHERE entityId=?"
)
b.ReportAllocs()
table := "UserLookup"
sb := str.NewStringBuilder()
for i := 0; i < b.N; i++ {
sb.WriteString(s1)
sb.WriteString(table)
sb.WriteString(s2)
sb.String()
sb.Reset()
}
}
func (this *StandardServerSelector) pickShardedServer(pool string,
table string, hintId int) (*mysql, error) {
const (
sb1 = "SELECT shardId,shardLock FROM "
sb2 = " WHERE entityId=?"
)
if hintId == 0 {
return nil, ErrInvalidHintId
}
// get mysql conn from cache
key := this.lookupCacheKey(pool, hintId)
if conn, present := this.lookupCache.Get(key); present {
return conn.(*mysql), nil
}
// cache missed, get lookup mysql conn
my, err := this.ServerByBucket(this.conf.LookupPool)
if err != nil {
return nil, err
}
// TODO maybe string concat is better performant
sb := str.NewStringBuilder()
sb.WriteString(sb1)
lookupTable := this.conf.LookupTable(pool)
if lookupTable == "" {
return nil, ErrLookupTableNotFound
}
sb.WriteString(lookupTable)
sb.WriteString(sb2)
rows, err := my.Query(sb.String(), hintId)
if err != nil {
log.Error("sql=%s id=%d: %s", sb.String(), hintId, err.Error())
return nil, err
}
defer rows.Close()
// only 1 row in lookup table
if !rows.Next() {
return nil, ErrShardLookupNotFound
}
var (
shardId string
shardLocked int
)
if err = rows.Scan(&shardId, &shardLocked); err != nil {
log.Error("sql=%s id=%d: %s", sb.String(), hintId, err.Error())
return nil, err
}
if shardLocked > 0 {
return nil, ErrEntityLocked
}
if err = rows.Err(); err != nil {
log.Error("sql=%s id=%d: %s", sb.String(), hintId, err.Error())
return nil, err
}
//bucket := fmt.Sprintf("%s%d", pool, (hintId/200000)+1)
bucket := pool + shardId
my, present := this.clients[bucket]
if !present {
return nil, ErrServerNotFound
}
this.lookupCache.Set(key, my)
log.Debug("lookupCache[%s] set {pool^%s}", key, bucket)
return my, nil
}