func Map(source *sublevel.DB, target *sublevel.DB, name string, mapFunc MappingFunc) *MappingTask {
task := &MappingTask{source: source, target: target, taskDb: sublevel.Sublevel(target.LevelDB(), name+string([]byte{0, 65})), mapFunc: mapFunc}
task.ro = levigo.NewReadOptions()
task.wo = levigo.NewWriteOptions()
filter := func(key, value []byte) []byte {
return key
}
f := func(key, value []byte) bool {
mapValues := new(bytes.Buffer)
if value != nil {
emit := func(key interface{}, value interface{}) {
k := serializeKey(key, uniclock.Next())
v := serializeValue(value)
task.target.Put(task.wo, k, v)
binary.Write(mapValues, binary.BigEndian, int32(len(k)))
mapValues.Write(k)
}
mapFunc(key, value, emit)
}
val, err := task.taskDb.Get(task.ro, key)
if err != nil {
return false
}
if val != nil {
valbuf := bytes.NewBuffer(val)
var l int32
off := 0
for off < len(val) {
err := binary.Read(valbuf, binary.BigEndian, &l)
if err != nil {
break
}
off += 4
if l < 0 || int(l) > len(val) {
panic("Something is very wrong with this data")
}
k := valbuf.Next(int(l))
off += int(l)
task.target.Delete(task.wo, k)
}
}
task.taskDb.Put(task.wo, key, mapValues.Bytes())
return true
}
task.task = runlevel.Trigger(source, sublevel.Sublevel(target.LevelDB(), name+string([]byte{0, 66})), filter, f)
return task
}
func Trigger(db *sublevel.DB, taskDb *sublevel.DB, filter FilterFunc, taskfunc ProcessFunc) *Task {
wo := levigo.NewWriteOptions()
ro := levigo.NewReadOptions()
task := &Task{db: db, filter: filter, processFunc: taskfunc, taskDb: taskDb, wo: wo, ro: ro, running: make(map[string]bool)}
var run func(taskKey []byte)
run = func(taskKey []byte) {
taskKeyStr := string(taskKey)
var ok bool
// println("RUN", string(key), string(value), string(taskKey))
hookfunc := func(key, value []byte, hook *sublevel.Hook) {
ok = taskfunc(key, value)
}
for {
it := task.taskDb.NewIterator(task.ro)
for it.Seek(taskKey); it.Valid(); it.Next() {
if !bytes.HasPrefix(it.Key(), taskKey) || len(taskKey)+16 != len(it.Key()) {
break
}
key := it.Value()
val, err := task.db.Get(task.ro, it.Value())
if err != nil {
continue
}
if len(val) == 0 {
val = nil
}
// println("RUN", string(key), string(val), string(taskKey))
// This lock avoids that the processing is interrupted by a call to Close()
task.closeMutex.Lock()
// Execute taskfunc in the context of a new hook, commit to disk, then call after
ok = true
db.RunHook(wo, hookfunc, nil, key, val)
if ok {
taskDb.Delete(wo, it.Key())
}
task.closeMutex.Unlock()
}
it.Close()
task.runningMutex.Lock()
state := task.running[taskKeyStr]
if !state {
delete(task.running, taskKeyStr)
task.runningMutex.Unlock()
break
}
task.running[taskKeyStr] = false
task.runningMutex.Unlock()
}
}
// Hook into the db to watch for changes
task.pre = func(key, value []byte, hook *sublevel.Hook) {
// println("PRE", string(key), string(value))
// Is this change relevant?
taskKey := filter(key, value)
if taskKey == nil {
return
}
// Write a DB row so the task is not forgotten if the system is terminated now
now := uniclock.Next()
nowBytes := []byte(fmt.Sprintf("%016x", now))
hook.Put(append(taskKey, nowBytes...), key, taskDb)
}
task.post = func(key, value []byte) {
// println("POST", string(key), string(value))
// Is this change relevant?
taskKey := filter(key, value)
if taskKey == nil {
return
}
taskKeyStr := string(taskKey)
// println("POSTtask", "'" + taskKeyStr + "'")
task.runningMutex.Lock()
defer task.runningMutex.Unlock()
if _, ok := task.running[taskKeyStr]; ok {
task.running[taskKeyStr] = true
} else {
task.running[taskKeyStr] = false
go run(taskKey)
}
}
db.Pre(task.pre)
db.Post(task.post)
return task
}