Implement queueing

Pipeline runs belonging to one repository now run sequentially. If a
pipeline run cannot start immediately, it is created as "pending", and a
process is started to periodically check if it can start.

Since the pipeline manager service may be restarted, it check on boot if
there are any pending runs for the repositories under its control and
starts the periodic check for those.

We can improve on the design by adding a signal in the finish task of a
pipeline run that the run will soon finish, reducing the up to 30s wait
time for the next run.

Closes #394.

internal/manager/bitbucket.go

@@ -86,3 +86,17 @@ func shouldSkip(bitbucketClient bitbucket.CommitClientInterface, projectKey, rep
 	}
 	return isCiSkipInCommitMessage(c.Message)
 }
+
+// getRepoNames retrieves the name of all repositories within the project
+// identified by projectKey.
+func getRepoNames(bitbucketClient bitbucket.RepoClientInterface, projectKey string) ([]string, error) {
+	repos := []string{}
+	rl, err := bitbucketClient.RepoList(projectKey)
+	if err != nil {
+		return repos, err
+	}
+	for _, n := range rl.Values {
+		repos = append(repos, n.Name)
+	}
+	return repos, nil
+}

internal/manager/pipeline.go

@@ -33,7 +33,7 @@ const (
 )
 
 // createPipelineRun creates a PipelineRun resource
-func createPipelineRun(tektonClient tektonClient.ClientPipelineRunInterface, ctxt context.Context, pData PipelineData) (*tekton.PipelineRun, error) {
+func createPipelineRun(tektonClient tektonClient.ClientPipelineRunInterface, ctxt context.Context, pData PipelineData, needQueueing bool) (*tekton.PipelineRun, error) {
 	pr, err := tektonClient.CreatePipelineRun(ctxt, &tekton.PipelineRun{
 		ObjectMeta: metav1.ObjectMeta{
 			GenerateName: fmt.Sprintf("%s-", pData.Name),
@@ -59,6 +59,9 @@ func createPipelineRun(tektonClient tektonClient.ClientPipelineRunInterface, ctx
 	if err != nil {
 		return nil, err
 	}
+	if needQueueing {
+		pr.Spec.Status = tekton.PipelineRunSpecStatusPending
+	}
 	return pr, nil
 }
 

internal/manager/queue.go

@@ -0,0 +1,143 @@
+package manager
+
+import (
+	"context"
+	"fmt"
+	"math/rand"
+	"sort"
+	"time"
+
+	tektonClient "github.com/opendevstack/pipeline/internal/tekton"
+	"github.com/opendevstack/pipeline/pkg/logging"
+	tekton "github.com/tektoncd/pipeline/pkg/apis/pipeline/v1beta1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+)
+
+// pipelineRunQueue manages multiple queues. These queues
+// can be polled in vertain intervals.
+type pipelineRunQueue struct {
+	queues       map[string]bool
+	pollInterval time.Duration
+	// logger is the logger to send logging messages to.
+	logger logging.LeveledLoggerInterface
+}
+
+// StartPolling periodically checks status for given identifier.
+// The time until the first time is not more than maxInitialWait.
+func (q *pipelineRunQueue) StartPolling(pt QueueAdvancer, identifier string, maxInitialWait time.Duration) chan bool {
+	quit := make(chan bool)
+	if q.queues[identifier] {
+		close(quit)
+		return quit
+	}
+	q.queues[identifier] = true
+
+	maxInitialWaitSeconds := int(maxInitialWait.Seconds())
+	var ticker *time.Ticker
+	if maxInitialWaitSeconds > 1 {
+		initialWaitSeconds := rand.Intn(maxInitialWaitSeconds-1) + 1
+		ticker = time.NewTicker(time.Duration(initialWaitSeconds) * time.Second)
+	} else {
+		ticker = time.NewTicker(time.Second)
+	}
+	go func() {
+		for {
+			select {
+			case <-quit:
+				q.queues[identifier] = false
+				ticker.Stop()
+				return
+			case <-ticker.C:
+				ticker.Stop()
+				ticker = time.NewTicker(q.pollInterval)
+				queueLength, err := pt.AdvanceQueue(identifier)
+				if err != nil {
+					q.logger.Warnf("error during poll tick: %s", err)
+				}
+				if queueLength == 0 {
+					close(quit)
+				}
+			}
+		}
+	}()
+
+	return quit
+}
+
+// QueueAdvancer is the interface passed to
+// *pipelineRunQueue#StartPolling.
+type QueueAdvancer interface {
+	// AdvanceQueue is called for each poll step.
+	AdvanceQueue(repository string) (int, error)
+}
+
+// Queue represents a pipeline run Queue. Pipelines of one repository must
+// not run in parallel.
+type Queue struct {
+	TektonClient tektonClient.ClientPipelineRunInterface
+}
+
+// needsQueueing checks if any run has either:
+// - pending status set OR
+// - is progressing
+func needsQueueing(pipelineRuns *tekton.PipelineRunList) bool {
+	for _, pr := range pipelineRuns.Items {
+		if pr.Spec.Status == tekton.PipelineRunSpecStatusPending || pipelineRunIsProgressing(pr) {
+			return true
+		}
+	}
+	return false
+}
+
+// AdvanceQueue starts the oldest pending pipeline run if there is no
+// progressing pipeline run at the moment.
+// It returns the queue length.
+func (s *Server) AdvanceQueue(repository string) (int, error) {
+	s.Mutex.Lock()
+	defer s.Mutex.Unlock()
+	ctxt, cancel := context.WithTimeout(context.Background(), 5*time.Minute)
+	defer cancel()
+	pipelineRuns, err := listPipelineRuns(s.TektonClient, ctxt, repository)
+	if err != nil {
+		return 0, fmt.Errorf("could not retrieve existing pipeline runs: %w", err)
+	}
+
+	var foundRunning bool
+	pendingPrs := []tekton.PipelineRun{}
+	for _, pr := range pipelineRuns.Items {
+		if pr.IsPending() {
+			pendingPrs = append(pendingPrs, pr)
+			continue
+		}
+		if pipelineRunIsProgressing(pr) {
+			foundRunning = true
+			continue
+		}
+	}
+
+	if !foundRunning && len(pendingPrs) > 0 {
+		// update oldest pending PR
+		sortPipelineRunsDescending(pendingPrs)
+		oldestPR := pendingPrs[len(pendingPrs)-1]
+		pendingPrs = pendingPrs[:len(pendingPrs)-1]
+		oldestPR.Spec.Status = "" // remove pending status -> starts pipeline run
+		_, err := s.TektonClient.UpdatePipelineRun(ctxt, &oldestPR, metav1.UpdateOptions{})
+		if err != nil {
+			return len(pendingPrs), fmt.Errorf("could not update pipeline run %s: %w", oldestPR.Name, err)
+		}
+	}
+	return len(pendingPrs), nil
+}
+
+// pipelineRunIsProgressing returns true if the PR is not done, not pending,
+// not cancelled, and not timed out.
+func pipelineRunIsProgressing(pr tekton.PipelineRun) bool {
+	return !(pr.IsDone() || pr.IsPending() || pr.IsCancelled() || pr.IsTimedOut())
+}
+
+// sortPipelineRunsDescending sorts pipeline runs by time (descending)
+func sortPipelineRunsDescending(pipelineRuns []tekton.PipelineRun) {
+	sort.Slice(pipelineRuns, func(i, j int) bool {
+		return pipelineRuns[j].CreationTimestamp.Time.Before(pipelineRuns[i].CreationTimestamp.Time)
+	})
+}