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service.go
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service.go
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package subscriber // import "github.com/influxdata/influxdb/services/subscriber"
import (
"expvar"
"fmt"
"log"
"net/url"
"os"
"strings"
"sync"
"github.com/influxdata/influxdb"
"github.com/influxdata/influxdb/cluster"
"github.com/influxdata/influxdb/services/meta"
)
// Statistics for the Subscriber service.
const (
statPointsWritten = "pointsWritten"
statWriteFailures = "writeFailures"
)
// PointsWriter is an interface for writing points to a subscription destination.
// Only WritePoints() needs to be satisfied.
type PointsWriter interface {
WritePoints(p *cluster.WritePointsRequest) error
}
// unique set that identifies a given subscription
type subEntry struct {
db string
rp string
name string
}
// Service manages forking the incoming data from InfluxDB
// to defined third party destinations.
// Subscriptions are defined per database and retention policy.
type Service struct {
subs map[subEntry]PointsWriter
MetaClient interface {
Databases() ([]meta.DatabaseInfo, error)
WaitForDataChanged() chan struct{}
}
NewPointsWriter func(u url.URL) (PointsWriter, error)
Logger *log.Logger
statMap *expvar.Map
points chan *cluster.WritePointsRequest
wg sync.WaitGroup
closed bool
closing chan struct{}
mu sync.Mutex
}
// NewService returns a subscriber service with given settings
func NewService(c Config) *Service {
return &Service{
subs: make(map[subEntry]PointsWriter),
NewPointsWriter: newPointsWriter,
Logger: log.New(os.Stderr, "[subscriber] ", log.LstdFlags),
statMap: influxdb.NewStatistics("subscriber", "subscriber", nil),
points: make(chan *cluster.WritePointsRequest),
closed: true,
closing: make(chan struct{}),
}
}
// Open starts the subscription service.
func (s *Service) Open() error {
s.mu.Lock()
defer s.mu.Unlock()
s.closing = make(chan struct{})
if s.MetaClient == nil {
panic("no meta store")
}
s.closed = false
// Perform initial update
s.Update()
s.wg.Add(1)
go s.writePoints()
// Do not wait for this goroutine since it block until a meta change occurs.
go s.waitForMetaUpdates()
s.Logger.Println("opened service")
return nil
}
// Close terminates the subscription service
func (s *Service) Close() error {
s.mu.Lock()
defer s.mu.Unlock()
close(s.points)
s.closed = true
select {
case <-s.closing:
// do nothing
default:
close(s.closing)
}
s.wg.Wait()
s.Logger.Println("closed service")
return nil
}
// SetLogger sets the internal logger to the logger passed in.
func (s *Service) SetLogger(l *log.Logger) {
s.Logger = l
}
func (s *Service) waitForMetaUpdates() {
for {
ch := s.MetaClient.WaitForDataChanged()
select {
case <-ch:
//Check that we haven't been closed before performing update.
s.mu.Lock()
if s.closed {
s.mu.Unlock()
s.Logger.Println("service closed not updating")
return
}
s.mu.Unlock()
s.Update()
case <-s.closing:
return
}
}
}
// Update will start new and stop deleted subscriptions.
func (s *Service) Update() error {
dbis, err := s.MetaClient.Databases()
if err != nil {
return err
}
allEntries := make(map[subEntry]bool, 0)
// Add in new subscriptions
for _, dbi := range dbis {
for _, rpi := range dbi.RetentionPolicies {
for _, si := range rpi.Subscriptions {
se := subEntry{
db: dbi.Name,
rp: rpi.Name,
name: si.Name,
}
allEntries[se] = true
if _, ok := s.subs[se]; ok {
continue
}
sub, err := s.createSubscription(se, si.Mode, si.Destinations)
if err != nil {
return err
}
s.subs[se] = sub
}
}
}
// Remove deleted subs
for se := range s.subs {
if !allEntries[se] {
delete(s.subs, se)
s.Logger.Println("deleted old subscription for", se.db, se.rp)
}
}
return nil
}
func (s *Service) createSubscription(se subEntry, mode string, destinations []string) (PointsWriter, error) {
var bm BalanceMode
switch mode {
case "ALL":
bm = ALL
case "ANY":
bm = ANY
default:
return nil, fmt.Errorf("unknown balance mode %q", mode)
}
writers := make([]PointsWriter, len(destinations))
statMaps := make([]*expvar.Map, len(writers))
for i, dest := range destinations {
u, err := url.Parse(dest)
if err != nil {
return nil, err
}
w, err := s.NewPointsWriter(*u)
if err != nil {
return nil, err
}
writers[i] = w
tags := map[string]string{
"database": se.db,
"retention_policy": se.rp,
"name": se.name,
"mode": mode,
"destination": dest,
}
key := strings.Join([]string{"subscriber", se.db, se.rp, se.name, dest}, ":")
statMaps[i] = influxdb.NewStatistics(key, "subscriber", tags)
}
s.Logger.Println("created new subscription for", se.db, se.rp)
return &balancewriter{
bm: bm,
writers: writers,
statMaps: statMaps,
}, nil
}
// Points returns a channel into which write point requests can be sent.
func (s *Service) Points() chan<- *cluster.WritePointsRequest {
return s.points
}
// read points off chan and write them
func (s *Service) writePoints() {
defer s.wg.Done()
for p := range s.points {
for se, sub := range s.subs {
if p.Database == se.db && p.RetentionPolicy == se.rp {
err := sub.WritePoints(p)
if err != nil {
s.Logger.Println(err)
s.statMap.Add(statWriteFailures, 1)
}
}
}
s.statMap.Add(statPointsWritten, int64(len(p.Points)))
}
}
// BalanceMode sets what balance mode to use on a subscription.
// valid options are currently ALL or ANY
type BalanceMode int
//ALL is a Balance mode option
const (
ALL BalanceMode = iota
ANY
)
// balances writes across PointsWriters according to BalanceMode
type balancewriter struct {
bm BalanceMode
writers []PointsWriter
statMaps []*expvar.Map
i int
}
func (b *balancewriter) WritePoints(p *cluster.WritePointsRequest) error {
var lastErr error
for range b.writers {
// round robin through destinations.
i := b.i
w := b.writers[i]
b.i = (b.i + 1) % len(b.writers)
// write points to destination.
err := w.WritePoints(p)
if err != nil {
lastErr = err
b.statMaps[i].Add(statWriteFailures, 1)
} else {
b.statMaps[i].Add(statPointsWritten, int64(len(p.Points)))
if b.bm == ANY {
break
}
}
}
return lastErr
}
// Creates a PointsWriter from the given URL
func newPointsWriter(u url.URL) (PointsWriter, error) {
switch u.Scheme {
case "udp":
return NewUDP(u.Host), nil
default:
return nil, fmt.Errorf("unknown destination scheme %s", u.Scheme)
}
}