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cache.go
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cache.go
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package mbt
import (
"os"
"runtime"
"sync"
"time"
"github.com/boltdb/bolt"
"github.com/buckhx/diglet/geo"
"github.com/buckhx/diglet/util"
"github.com/buckhx/tiles"
"gopkg.in/vmihailenco/msgpack.v2"
)
var (
featureBucket = []byte("feature")
)
type tileFeatures struct {
t tiles.Tile
f []*geo.Feature
}
type fID []byte
type featureIndex struct {
path string
db *bolt.DB
idx tiles.TileIndex
}
func newFeatureCache(path string) (c *featureIndex, err error) {
// TODO rm path first just to make sure we don't reuse any data
db, err := bolt.Open(path, 0600, &bolt.Options{Timeout: 5 * time.Second})
if err != nil {
return
}
if err = db.Update(func(tx *bolt.Tx) error {
_, err = tx.CreateBucketIfNotExists(featureBucket)
return err
}); err != nil {
return
}
c = &featureIndex{path: path, db: db, idx: tiles.NewSuffixIndex()}
return
}
func (c *featureIndex) tileFeatures(zmin, zmax int) <-chan tileFeatures {
tfs := make(chan tileFeatures, 1<<10)
rng := make(chan tiles.Tile, 1<<10)
go func() {
//TileRange isn't threadsafe
defer close(rng)
for t := range c.idx.TileRange(zmin, zmax) {
rng <- t
}
}()
p := runtime.GOMAXPROCS(0)
wg := &sync.WaitGroup{}
wg.Add(p)
for i := 0; i < p; i++ {
go func() {
defer wg.Done()
for t := range rng {
fids := c.idx.Values(t)
c.db.View(func(tx *bolt.Tx) error {
b := tx.Bucket(featureBucket)
tf := tileFeatures{t: t, f: make([]*geo.Feature, len(fids))}
for i, f := range fids {
k := f.(fID)
v := b.Get(k)
err := msgpack.Unmarshal(v, &tf.f[i])
util.Check(err)
}
tfs <- tf
return nil
})
}
}()
}
go func() {
wg.Wait()
close(tfs)
}()
return tfs
}
func (c *featureIndex) indexFeatures(features <-chan *geo.Feature, zoom int) {
records := make(chan *geo.Feature, 1<<10)
go func() {
defer close(records)
for f := range features {
k, err := key(f)
if err != nil {
util.Warn(err, "key err")
continue
}
records <- f
//TODO parallelize
for _, t := range FeatureTiles(f, zoom) {
c.idx.Add(t, k)
}
}
}()
c.addRecords(featureBucket, records)
}
func (c *featureIndex) addRecords(bucket []byte, recs <-chan *geo.Feature) {
i := 0
capacity := 1 << 16 //BlockSize
batch := make([]*geo.Feature, capacity)
for rec := range recs {
n := i % capacity
if n == 0 && i > 0 {
err := c.flush(bucket, batch)
util.Warn(err, "batch error")
}
batch[n] = rec
i++
}
err := c.flush(bucket, batch[:i%capacity])
util.Warn(err, "batch error")
util.Info("Added %d %ss", i, bucket)
}
// Write an ordered key
func (c *featureIndex) flush(bucket []byte, recs []*geo.Feature) error {
if len(recs) < 1 {
util.Info("Flushing empty batch, skipping")
return nil
}
util.Info("Flushing batch %s %v -> %v", bucket, recs[0].ID, recs[len(recs)-1].ID)
return c.db.Batch(func(tx *bolt.Tx) error {
b := tx.Bucket(bucket)
for _, rec := range recs {
k, v := keyed(rec)
err := b.Put(k, v)
if err != nil {
return err
}
}
return nil
})
}
func (c *featureIndex) close() {
c.db.Close()
os.Remove(c.path)
}
func keyed(f *geo.Feature) (k, v []byte) {
k, err := msgpack.Marshal(f.ID)
if err != nil {
return
}
v, err = msgpack.Marshal(f)
if err != nil {
k = nil
}
return
}
func key(f *geo.Feature) (fID, error) {
k, err := msgpack.Marshal(f.ID)
return fID(k), err
}