add other session providers (#5963)

vendor/github.com/couchbaselabs/go-couchbase/tap.go

@@ -0,0 +1,143 @@
+package couchbase
+
+import (
+	"github.com/couchbase/gomemcached/client"
+	"github.com/couchbase/goutils/logging"
+	"sync"
+	"time"
+)
+
+const initialRetryInterval = 1 * time.Second
+const maximumRetryInterval = 30 * time.Second
+
+// A TapFeed streams mutation events from a bucket.
+//
+// Events from the bucket can be read from the channel 'C'.  Remember
+// to call Close() on it when you're done, unless its channel has
+// closed itself already.
+type TapFeed struct {
+	C <-chan memcached.TapEvent
+
+	bucket    *Bucket
+	args      *memcached.TapArguments
+	nodeFeeds []*memcached.TapFeed    // The TAP feeds of the individual nodes
+	output    chan memcached.TapEvent // Same as C but writeably-typed
+	wg        sync.WaitGroup
+	quit      chan bool
+}
+
+// StartTapFeed creates and starts a new Tap feed
+func (b *Bucket) StartTapFeed(args *memcached.TapArguments) (*TapFeed, error) {
+	if args == nil {
+		defaultArgs := memcached.DefaultTapArguments()
+		args = &defaultArgs
+	}
+
+	feed := &TapFeed{
+		bucket: b,
+		args:   args,
+		output: make(chan memcached.TapEvent, 10),
+		quit:   make(chan bool),
+	}
+
+	go feed.run()
+
+	feed.C = feed.output
+	return feed, nil
+}
+
+// Goroutine that runs the feed
+func (feed *TapFeed) run() {
+	retryInterval := initialRetryInterval
+	bucketOK := true
+	for {
+		// Connect to the TAP feed of each server node:
+		if bucketOK {
+			killSwitch, err := feed.connectToNodes()
+			if err == nil {
+				// Run until one of the sub-feeds fails:
+				select {
+				case <-killSwitch:
+				case <-feed.quit:
+					return
+				}
+				feed.closeNodeFeeds()
+				retryInterval = initialRetryInterval
+			}
+		}
+
+		// On error, try to refresh the bucket in case the list of nodes changed:
+		logging.Infof("go-couchbase: TAP connection lost; reconnecting to bucket %q in %v",
+			feed.bucket.Name, retryInterval)
+		err := feed.bucket.Refresh()
+		bucketOK = err == nil
+
+		select {
+		case <-time.After(retryInterval):
+		case <-feed.quit:
+			return
+		}
+		if retryInterval *= 2; retryInterval > maximumRetryInterval {
+			retryInterval = maximumRetryInterval
+		}
+	}
+}
+
+func (feed *TapFeed) connectToNodes() (killSwitch chan bool, err error) {
+	killSwitch = make(chan bool)
+	for _, serverConn := range feed.bucket.getConnPools(false /* not already locked */) {
+		var singleFeed *memcached.TapFeed
+		singleFeed, err = serverConn.StartTapFeed(feed.args)
+		if err != nil {
+			logging.Errorf("go-couchbase: Error connecting to tap feed of %s: %v", serverConn.host, err)
+			feed.closeNodeFeeds()
+			return
+		}
+		feed.nodeFeeds = append(feed.nodeFeeds, singleFeed)
+		go feed.forwardTapEvents(singleFeed, killSwitch, serverConn.host)
+		feed.wg.Add(1)
+	}
+	return
+}
+
+// Goroutine that forwards Tap events from a single node's feed to the aggregate feed.
+func (feed *TapFeed) forwardTapEvents(singleFeed *memcached.TapFeed, killSwitch chan bool, host string) {
+	defer feed.wg.Done()
+	for {
+		select {
+		case event, ok := <-singleFeed.C:
+			if !ok {
+				if singleFeed.Error != nil {
+					logging.Errorf("go-couchbase: Tap feed from %s failed: %v", host, singleFeed.Error)
+				}
+				killSwitch <- true
+				return
+			}
+			feed.output <- event
+		case <-feed.quit:
+			return
+		}
+	}
+}
+
+func (feed *TapFeed) closeNodeFeeds() {
+	for _, f := range feed.nodeFeeds {
+		f.Close()
+	}
+	feed.nodeFeeds = nil
+}
+
+// Close a Tap feed.
+func (feed *TapFeed) Close() error {
+	select {
+	case <-feed.quit:
+		return nil
+	default:
+	}
+
+	feed.closeNodeFeeds()
+	close(feed.quit)
+	feed.wg.Wait()
+	close(feed.output)
+	return nil
+}