add func for leader endpoint(patroni) and call it after syncing statefulset and before syncing roles

Author: Schmaetz

pkg/cluster/cluster.go

@@ -1272,6 +1272,42 @@ func syncResources(a, b *v1.ResourceRequirements) bool {
 	return false
 }
 
+func (c *Cluster) waitForLeader(timeout time.Duration) error {
+	c.logger.Debugf("waiting up to %v for Patroni leader...", timeout)
+
+	deadline := time.Now().Add(timeout)
+	ticker := time.NewTicker(2 * time.Second)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-ticker.C:
+			if time.Now().After(deadline) {
+				return fmt.Errorf("timeout waiting for Patroni leader")
+			}
+
+			pods, err := c.listPodsOfType(TYPE_POSTGRESQL)
+			if err != nil {
+				continue
+			}
+
+			for _, pod := range pods {
+				isLeader, err := c.patroni.IsLeader(&pod)
+
+				if err != nil {
+					c.logger.Debugf("check leader failed for %s: %v", pod.Name, err)
+					continue
+				}
+
+				if isLeader {
+					c.logger.Infof("Patroni leader found: %s. Proceeding with DB sync.", pod.Name)
+					return nil
+				}
+			}
+		}
+	}
+}
+
 // Delete deletes the cluster and cleans up all objects associated with it (including statefulsets).
 // The deletion order here is somewhat significant, because Patroni, when running with the Kubernetes
 // DCS, reuses the master's endpoint to store the leader related metadata. If we remove the endpoint

pkg/cluster/sync.go

@@ -261,22 +261,46 @@ func (c *Cluster) Sync(newSpec *cpov1.Postgresql) error {
 		return err
 	}
 
+	// Check if Cluster has an Leader
+	needDBAccess := !(c.databaseAccessDisabled() || c.getNumberOfInstances(&newSpec.Spec) <= 0 || c.Spec.StandbyCluster != nil || c.restoreInProgress())
 	// create database objects unless we are running without pods or disabled that feature explicitly
-	if !(c.databaseAccessDisabled() || c.getNumberOfInstances(&newSpec.Spec) <= 0 || c.Spec.StandbyCluster != nil || c.restoreInProgress()) {
+	if needDBAccess {
+		if err := c.waitForLeader(60 * time.Second); err != nil {
+			c.logger.Infof("Postgres not yet ready for writes (Patroni leader election pending?). Skipping DB sync until next loop: %v", err)
+			return nil
+		}
+
 		c.logger.Debug("syncing roles")
 		if err = c.syncRoles(); err != nil {
 			c.logger.Errorf("could not sync roles: %v", err)
 		}
+
 		c.logger.Debug("syncing databases")
 		if err = c.syncDatabases(); err != nil {
 			c.logger.Errorf("could not sync databases: %v", err)
 		}
+
 		c.logger.Debug("syncing prepared databases with schemas")
 		if err = c.syncPreparedDatabases(); err != nil {
 			c.logger.Errorf("could not sync prepared database: %v", err)
 		}
 	}
 
+	// if !(c.databaseAccessDisabled() || c.getNumberOfInstances(&newSpec.Spec) <= 0 || c.Spec.StandbyCluster != nil || c.restoreInProgress()) {
+	// 	c.logger.Debug("syncing roles")
+	// 	if err = c.syncRoles(); err != nil {
+	// 		c.logger.Errorf("could not sync roles: %v", err)
+	// 	}
+	// 	c.logger.Debug("syncing databases")
+	// 	if err = c.syncDatabases(); err != nil {
+	// 		c.logger.Errorf("could not sync databases: %v", err)
+	// 	}
+	// 	c.logger.Debug("syncing prepared databases with schemas")
+	// 	if err = c.syncPreparedDatabases(); err != nil {
+	// 		c.logger.Errorf("could not sync prepared database: %v", err)
+	// 	}
+	// }
+
 	// sync connection pooler
 	if _, err = c.syncConnectionPooler(&oldSpec, newSpec, c.installLookupFunction); err != nil {
 		return fmt.Errorf("could not sync connection pooler: %v", err)

pkg/util/patroni/patroni.go

@@ -14,8 +14,8 @@ import (
 	"github.com/cybertec-postgresql/cybertec-pg-operator/pkg/util/constants"
 	httpclient "github.com/cybertec-postgresql/cybertec-pg-operator/pkg/util/httpclient"
 
-	"github.com/sirupsen/logrus"
 	cpov1 "github.com/cybertec-postgresql/cybertec-pg-operator/pkg/apis/cpo.opensource.cybertec.at/v1"
+	"github.com/sirupsen/logrus"
 	v1 "k8s.io/api/core/v1"
 )
 
@@ -25,6 +25,7 @@ const (
 	clusterPath  = "/cluster"
 	statusPath   = "/patroni"
 	restartPath  = "/restart"
+	leaderPath   = "/leader"
 	ApiPort      = 8008
 	timeout      = 30 * time.Second
 )
@@ -38,6 +39,7 @@ type Interface interface {
 	Restart(server *v1.Pod) error
 	GetConfig(server *v1.Pod) (cpov1.Patroni, map[string]string, error)
 	SetConfig(server *v1.Pod, config map[string]interface{}) error
+	IsLeader(server *v1.Pod) (bool, error)
 }
 
 // Patroni API client
@@ -150,7 +152,7 @@ func (p *Patroni) Switchover(master *v1.Pod, candidate string) error {
 
 //TODO: add an option call /patroni to check if it is necessary to restart the server
 
-//SetPostgresParameters sets Postgres options via Patroni patch API call.
+// SetPostgresParameters sets Postgres options via Patroni patch API call.
 func (p *Patroni) SetPostgresParameters(server *v1.Pod, parameters map[string]string) error {
 	buf := &bytes.Buffer{}
 	err := json.NewEncoder(buf).Encode(map[string]map[string]interface{}{"postgresql": {"parameters": parameters}})
@@ -164,7 +166,7 @@ func (p *Patroni) SetPostgresParameters(server *v1.Pod, parameters map[string]st
 	return p.httpPostOrPatch(http.MethodPatch, apiURLString+configPath, buf)
 }
 
-//SetConfig sets Patroni options via Patroni patch API call.
+// SetConfig sets Patroni options via Patroni patch API call.
 func (p *Patroni) SetConfig(server *v1.Pod, config map[string]interface{}) error {
 	buf := &bytes.Buffer{}
 	err := json.NewEncoder(buf).Encode(config)
@@ -320,3 +322,24 @@ func (p *Patroni) GetMemberData(server *v1.Pod) (MemberData, error) {
 
 	return data, nil
 }
+
+// Call leader-Endpoint (expecting statuscode 200 or 503)
+func (p *Patroni) IsLeader(server *v1.Pod) (bool, error) {
+	apiURLString, err := apiURL(server)
+	if err != nil {
+		return false, err
+	}
+
+	resp, err := p.httpClient.Get(apiURLString + leaderPath)
+	if err != nil {
+		return false, fmt.Errorf("request failed: %v", err)
+	}
+	defer resp.Body.Close()
+
+	// 200 = Leader, 503 = Replica
+	if resp.StatusCode == http.StatusOK {
+		return true, nil
+	}
+
+	return false, nil
+}