Add first queue implementation

queue/queue.go

@@ -0,0 +1,98 @@
+package queue
+
+import (
+	"time"
+
+	"github.com/rqlite/rqlite/command"
+)
+
+type Execer interface {
+	Execute(er *command.ExecuteRequest) ([]*command.ExecuteResult, error)
+}
+
+type Queue struct {
+	maxSize   int
+	batchSize int
+	timeout   time.Duration
+	store     Execer
+
+	c      chan *command.Statement
+	done   chan struct{}
+	closed chan struct{}
+	flush  chan struct{}
+}
+
+func New(maxSize, batchSize int, t time.Duration, e Execer) *Queue {
+	q := &Queue{
+		maxSize:   maxSize,
+		batchSize: batchSize,
+		timeout:   t,
+		store:     e,
+		c:         make(chan *command.Statement, maxSize),
+		done:      make(chan struct{}),
+		closed:    make(chan struct{}),
+	}
+
+	go q.run()
+	return q
+}
+
+func (q *Queue) Write(stmt *command.Statement) error {
+	q.c <- stmt
+	return nil
+}
+
+func (q *Queue) Flush() error {
+	q.flush <- struct{}{}
+	return nil
+}
+
+func (q *Queue) Close() error {
+	close(q.done)
+	<-q.closed
+	return nil
+}
+
+func (q *Queue) run() {
+	defer close(q.closed)
+	stmts := make([]*command.Statement, 0)
+	//ticker := time.NewTicker(q.timeout)
+
+	writeFn := func(stmts []*command.Statement) {
+		q.exec(stmts)
+		stmts = make([]*command.Statement, 0)
+	}
+
+	for {
+		select {
+		case s := <-q.c:
+			stmts = append(stmts, s)
+			if len(stmts) == q.batchSize {
+				writeFn(stmts)
+			}
+		// case <-ticker.C:
+		// 	// check batch, flush if empty. Not quite right. Timeout should expire when first item added?
+		case <-q.flush:
+			writeFn(stmts)
+		case <-q.done:
+			return
+		}
+	}
+}
+
+func (q *Queue) exec(stmts []*command.Statement) error {
+	if stmts == nil || len(stmts) == 0 {
+		return nil
+	}
+
+	er := &command.ExecuteRequest{
+		Request: &command.Request{
+			Statements: stmts,
+		},
+	}
+
+	// Doesn't handle leader-redirect, transparent forwarding, etc.
+	// Would need a "wrapped" store which handles it.
+	_, err := q.store.Execute(er)
+	return err
+}

queue/queue_test.go

@@ -0,0 +1,13 @@
+package queue
+
+import (
+	"testing"
+	"time"
+)
+
+func Test_NewQueue(t *testing.T) {
+	q := New(1, 1, 100*time.Millisecond, nil)
+	if q == nil {
+		t.Fatalf("failed to create new Queue")
+	}
+}