Example #1
0
func (p *PostgresKeeper) createPGParameters(db *cluster.DB) common.Parameters {
	parameters := common.Parameters{}

	// Include init parameters if include config is required
	if db.Spec.IncludeConfig {
		for k, v := range p.dbLocalState.InitPGParameters {
			parameters[k] = v
		}
	}

	// Copy user defined pg parameters
	for k, v := range db.Spec.PGParameters {
		parameters[k] = v
	}

	// Add/Replace mandatory PGParameters
	for k, v := range mandatoryPGParameters {
		parameters[k] = v
	}

	parameters["listen_addresses"] = fmt.Sprintf("127.0.0.1,%s", p.pgListenAddress)
	parameters["port"] = p.pgPort
	// TODO(sgotti) max_replication_slots needs to be at least the
	// number of existing replication slots or startup will
	// fail.
	// TODO(sgotti) changing max_replication_slots requires an
	// instance restart.
	parameters["max_replication_slots"] = strconv.FormatUint(uint64(db.Spec.MaxStandbys), 10)
	// Add some more wal senders, since also the keeper will use them
	// TODO(sgotti) changing max_wal_senders requires an instance restart.
	parameters["max_wal_senders"] = strconv.FormatUint(uint64(db.Spec.MaxStandbys+2), 10)

	// required by pg_rewind (if data checksum is enabled it's ignored)
	if db.Spec.UsePgrewind {
		parameters["wal_log_hints"] = "on"
	}

	// Setup synchronous replication
	if db.Spec.SynchronousReplication && len(db.Spec.SynchronousStandbys) > 0 {
		synchronousStandbys := []string{}
		for _, synchronousStandby := range db.Spec.SynchronousStandbys {
			synchronousStandbys = append(synchronousStandbys, common.StolonName(synchronousStandby))
		}
		// TODO(sgotti) Find a way to detect the pg major version also
		// when the instance is empty. Parsing the postgres --version
		// is not always reliable (for example we can get `10devel` for
		// development version).
		// Now this will lead to problems starting the instance (or
		// warning reloading the parameters) with postgresql < 9.6
		if len(synchronousStandbys) > 1 {
			parameters["synchronous_standby_names"] = fmt.Sprintf("%d (%s)", len(synchronousStandbys), strings.Join(synchronousStandbys, ","))
		} else {
			parameters["synchronous_standby_names"] = strings.Join(synchronousStandbys, ",")
		}
	} else {
		parameters["synchronous_standby_names"] = ""
	}

	return parameters
}
Example #2
0
func (p *PostgresKeeper) getReplConnParams(db, followedDB *cluster.DB) pg.ConnParams {
	return pg.ConnParams{
		"user":             p.pgReplUsername,
		"password":         p.pgReplPassword,
		"host":             followedDB.Status.ListenAddress,
		"port":             followedDB.Status.Port,
		"application_name": common.StolonName(db.UID),
		"sslmode":          "disable",
	}
}
Example #3
0
func (p *PostgresKeeper) createPGParameters(db *cluster.DB) common.Parameters {
	parameters := common.Parameters{}

	// Include init parameters if include config is required
	if db.Spec.IncludeConfig {
		for k, v := range p.dbLocalState.InitPGParameters {
			parameters[k] = v
		}
	}

	// Copy user defined pg parameters
	for k, v := range db.Spec.PGParameters {
		parameters[k] = v
	}

	// Add/Replace mandatory PGParameters
	for k, v := range mandatoryPGParameters {
		parameters[k] = v
	}

	parameters["listen_addresses"] = fmt.Sprintf("127.0.0.1,%s", p.pgListenAddress)
	parameters["port"] = p.pgPort
	// TODO(sgotti) max_replication_slots needs to be at least the
	// number of existing replication slots or startup will
	// fail.
	// TODO(sgotti) changing max_replication_slots requires an
	// instance restart.
	parameters["max_replication_slots"] = strconv.FormatUint(uint64(db.Spec.MaxStandbys), 10)
	// Add some more wal senders, since also the keeper will use them
	// TODO(sgotti) changing max_wal_senders requires an instance restart.
	parameters["max_wal_senders"] = strconv.FormatUint(uint64(db.Spec.MaxStandbys+2), 10)

	// required by pg_rewind (if data checksum is enabled it's ignored)
	if db.Spec.UsePgrewind {
		parameters["wal_log_hints"] = "on"
	}

	// Setup synchronous replication
	if db.Spec.SynchronousReplication {
		standbyNames := []string{}
		for _, follower := range db.Spec.Followers {
			standbyNames = append(standbyNames, common.StolonName(follower))
		}
		parameters["synchronous_standby_names"] = strings.Join(standbyNames, ",")
	} else {
		parameters["synchronous_standby_names"] = ""
	}

	return parameters
}
Example #4
0
func (p *PostgresKeeper) postgresKeeperSM(pctx context.Context) {
	e := p.e
	pgm := p.pgm

	cd, _, err := e.GetClusterData()
	if err != nil {
		log.Error("error retrieving cluster data", zap.Error(err))
		return
	}
	log.Debug("cd dump", zap.String("cd", spew.Sdump(cd)))

	if cd == nil {
		log.Info("no cluster data available, waiting for it to appear")
		return
	}
	if cd.FormatVersion != cluster.CurrentCDFormatVersion {
		log.Error("unsupported clusterdata format version", zap.Uint64("version", cd.FormatVersion))
		return
	}
	if cd.Cluster != nil {
		p.sleepInterval = cd.Cluster.Spec.SleepInterval.Duration
		p.requestTimeout = cd.Cluster.Spec.RequestTimeout.Duration

		if p.keeperLocalState.ClusterUID != cd.Cluster.UID {
			p.keeperLocalState.ClusterUID = cd.Cluster.UID
			if err = p.saveKeeperLocalState(); err != nil {
				log.Error("error", zap.Error(err))
				return
			}
		}
	}

	k, ok := cd.Keepers[p.keeperLocalState.UID]
	if !ok {
		log.Info("our keeper data is not available, waiting for it to appear")
		return
	}
	// TODO(sgotti) Check that the Keeper.Status address:port has been updated

	db := cd.FindDB(k)
	if db == nil {
		log.Info("no db assigned")
		return
	}
	// TODO(sgotti) Check that the DB.Status address:port has been updated

	followersUIDs := db.Spec.Followers

	prevPGParameters := pgm.GetParameters()
	// create postgres parameteres
	pgParameters := p.createPGParameters(db)
	// update pgm postgres parameters
	pgm.SetParameters(pgParameters)

	dbls := p.dbLocalState
	if dbls.Initializing {
		// If we are here this means that the db initialization or
		// resync as failed so we have to clean up stale data
		log.Error("db failed to initialize or resync")
		// Clean up cluster db datadir
		if err = pgm.RemoveAll(); err != nil {
			log.Error("failed to remove the postgres data dir", zap.Error(err))
			return
		}
		// Reset current db local state since it's not valid anymore
		p.localStateMutex.Lock()
		dbls.UID = ""
		dbls.Generation = cluster.NoGeneration
		dbls.Initializing = false
		p.localStateMutex.Unlock()
		if err = p.saveDBLocalState(); err != nil {
			log.Error("error", zap.Error(err))
			return
		}
	}

	initialized, err := pgm.IsInitialized()
	if err != nil {
		log.Error("failed to detect if instance is initialized", zap.Error(err))
		return
	}

	started := false
	if initialized {
		started, err = pgm.IsStarted()
		if err != nil {
			// log error getting instance state but go ahead.
			log.Info("failed to retrieve instance status", zap.Error(err))
		}
	}

	log.Debug("db status", zap.Bool("started", started))

	// if the db is initialized but there isn't a db local state then generate a new one
	if initialized && dbls.UID == "" {
		p.localStateMutex.Lock()
		dbls.UID = common.UID()
		dbls.Generation = cluster.NoGeneration
		dbls.InitPGParameters = nil
		dbls.Initializing = false
		p.localStateMutex.Unlock()
		if err = p.saveDBLocalState(); err != nil {
			log.Error("error", zap.Error(err))
			return
		}
	}

	if dbls.UID != db.UID {
		log.Info("current db UID different than cluster data db UID", zap.String("db", dbls.UID), zap.String("cdDB", db.UID))
		switch db.Spec.InitMode {
		case cluster.DBInitModeNew:
			log.Info("initializing the database cluster")
			p.localStateMutex.Lock()
			dbls.UID = db.UID
			// Set a no generation since we aren't already converged.
			dbls.Generation = cluster.NoGeneration
			dbls.InitPGParameters = nil
			dbls.Initializing = true
			p.localStateMutex.Unlock()
			if err = p.saveDBLocalState(); err != nil {
				log.Error("error", zap.Error(err))
				return
			}
			if started {
				if err = pgm.Stop(true); err != nil {
					log.Error("failed to stop pg instance", zap.Error(err))
					return
				}
				started = false
			}
			if err = pgm.RemoveAll(); err != nil {
				log.Error("failed to remove the postgres data dir", zap.Error(err))
				return
			}
			if err = pgm.Init(); err != nil {
				log.Error("failed to initialize postgres database cluster", zap.Error(err))
				return
			}
			initialized = true

			if db.Spec.IncludeConfig {
				if err = pgm.StartTmpMerged(); err != nil {
					log.Error("failed to start instance", zap.Error(err))
					return
				}
				pgParameters, err = pgm.GetConfigFilePGParameters()
				if err != nil {
					log.Error("failed to rename previous postgresql.conf", zap.Error(err))
					return
				}
				p.localStateMutex.Lock()
				dbls.InitPGParameters = pgParameters
				p.localStateMutex.Unlock()
			} else {
				if err = pgm.StartTmpMerged(); err != nil {
					log.Error("failed to start instance", zap.Error(err))
					return
				}
			}

			log.Info("setting roles")
			if err = pgm.SetupRoles(); err != nil {
				log.Error("failed to setup roles", zap.Error(err))
				return
			}

			if err = p.saveDBLocalState(); err != nil {
				log.Error("error", zap.Error(err))
				return
			}
			if err = pgm.Stop(true); err != nil {
				log.Error("failed to stop pg instance", zap.Error(err))
				return
			}
		case cluster.DBInitModePITR:
			log.Info("restoring the database cluster")
			p.localStateMutex.Lock()
			dbls.UID = db.UID
			// Set a no generation since we aren't already converged.
			dbls.Generation = cluster.NoGeneration
			dbls.InitPGParameters = nil
			dbls.Initializing = true
			p.localStateMutex.Unlock()
			if err = p.saveDBLocalState(); err != nil {
				log.Error("error", zap.Error(err))
				return
			}
			if started {
				if err = pgm.Stop(true); err != nil {
					log.Error("failed to stop pg instance", zap.Error(err))
					return
				}
				started = false
			}
			if err = pgm.RemoveAll(); err != nil {
				log.Error("failed to remove the postgres data dir", zap.Error(err))
				return
			}
			if err = pgm.Restore(db.Spec.PITRConfig.DataRestoreCommand); err != nil {
				log.Error("failed to restore postgres database cluster", zap.Error(err))
				return
			}
			if err = pgm.WriteRecoveryConf(p.createRecoveryParameters(nil, db.Spec.PITRConfig.ArchiveRecoverySettings)); err != nil {
				log.Error("err", zap.Error(err))
				return
			}
			if db.Spec.IncludeConfig {
				if err = pgm.StartTmpMerged(); err != nil {
					log.Error("failed to start instance", zap.Error(err))
					return
				}
				pgParameters, err = pgm.GetConfigFilePGParameters()
				if err != nil {
					log.Error("failed to rename previous postgresql.conf", zap.Error(err))
					return
				}
				p.localStateMutex.Lock()
				dbls.InitPGParameters = pgParameters
				p.localStateMutex.Unlock()
			} else {
				if err = pgm.StartTmpMerged(); err != nil {
					log.Error("failed to start instance", zap.Error(err))
					return
				}
			}
			initialized = true

			if err = p.saveDBLocalState(); err != nil {
				log.Error("error", zap.Error(err))
				return
			}
			if err = pgm.Stop(true); err != nil {
				log.Error("failed to stop pg instance", zap.Error(err))
				return
			}
		case cluster.DBInitModeExisting:
			// replace our current db uid with the required one.
			p.localStateMutex.Lock()
			dbls.UID = db.UID
			// Set a no generation since we aren't already converged.
			dbls.Generation = cluster.NoGeneration
			dbls.InitPGParameters = nil
			p.localStateMutex.Unlock()
			if err = p.saveDBLocalState(); err != nil {
				log.Error("error", zap.Error(err))
				return
			}
			if started {
				if err = pgm.Stop(true); err != nil {
					log.Error("failed to stop pg instance", zap.Error(err))
					return
				}
				started = false
			}
			if db.Spec.IncludeConfig {
				if err = pgm.StartTmpMerged(); err != nil {
					log.Error("failed to start instance", zap.Error(err))
					return
				}
				pgParameters, err = pgm.GetConfigFilePGParameters()
				if err != nil {
					log.Error("failed to rename previous postgresql.conf", zap.Error(err))
					return
				}
				p.localStateMutex.Lock()
				dbls.InitPGParameters = pgParameters
				p.localStateMutex.Unlock()
			} else {
				if err = pgm.StartTmpMerged(); err != nil {
					log.Error("failed to start instance", zap.Error(err))
					return
				}
			}
			log.Info("updating our db UID with the cluster data provided db UID")
			// replace our current db uid with the required one.
			p.localStateMutex.Lock()
			dbls.InitPGParameters = pgParameters
			p.localStateMutex.Unlock()
			if err = p.saveDBLocalState(); err != nil {
				log.Error("error", zap.Error(err))
				return
			}
			if err = pgm.Stop(true); err != nil {
				log.Error("failed to stop pg instance", zap.Error(err))
				return
			}
		case cluster.DBInitModeNone:
			// replace our current db uid with the required one.
			p.localStateMutex.Lock()
			dbls.UID = db.UID
			// Set a no generation since we aren't already converged.
			dbls.Generation = cluster.NoGeneration
			dbls.InitPGParameters = nil
			p.localStateMutex.Unlock()
			if err = p.saveDBLocalState(); err != nil {
				log.Error("error", zap.Error(err))
				return
			}
			return
		default:
			log.Error("unknown db init mode", zap.String("initMode", string(db.Spec.InitMode)))
			return
		}
	}

	pgm.SetParameters(pgParameters)

	var localRole common.Role
	var systemID string
	if !initialized {
		log.Info("database cluster not initialized")
		localRole = common.RoleUndefined
	} else {
		localRole, err = pgm.GetRole()
		if err != nil {
			log.Error("error retrieving current pg role", zap.Error(err))
			return
		}
		systemID, err = p.pgm.GetSystemdID()
		if err != nil {
			log.Error("error retrieving systemd ID", zap.Error(err))
			return
		}
	}

	targetRole := db.Spec.Role
	log.Debug("target role", zap.String("targetRole", string(targetRole)))

	switch targetRole {
	case common.RoleMaster:
		// We are the elected master
		log.Info("our db requested role is master")
		if localRole == common.RoleUndefined {
			log.Error("database cluster not initialized but requested role is master. This shouldn't happen!")
			return
		}
		if !started {
			if err = pgm.Start(); err != nil {
				log.Error("failed to start postgres", zap.Error(err))
				return
			}
			started = true
		}

		if localRole == common.RoleStandby {
			log.Info("promoting to master")
			if err = pgm.Promote(); err != nil {
				log.Error("err", zap.Error(err))
				return
			}
		} else {
			log.Info("already master")
		}

		var replSlots []string
		replSlots, err = pgm.GetReplicatinSlots()
		log.Debug("replication slots", zap.Object("replSlots", replSlots))
		if err != nil {
			log.Error("err", zap.Error(err))
			return
		}
		// Drop replication slots
		for _, slotName := range replSlots {
			if !common.IsStolonName(slotName) {
				continue
			}
			if !util.StringInSlice(followersUIDs, common.NameFromStolonName(slotName)) {
				log.Info("dropping replication slot since db not marked as follower", zap.String("slot", slotName), zap.String("db", common.NameFromStolonName(slotName)))
				if err = pgm.DropReplicationSlot(slotName); err != nil {
					log.Error("err", zap.Error(err))
				}
			}
		}
		// Create replication slots
		for _, followerUID := range followersUIDs {
			if followerUID == dbls.UID {
				continue
			}
			replSlot := common.StolonName(followerUID)
			if !util.StringInSlice(replSlots, replSlot) {
				log.Info("creating replication slot", zap.String("slot", replSlot), zap.String("db", followerUID))
				if err = pgm.CreateReplicationSlot(replSlot); err != nil {
					log.Error("err", zap.Error(err))
				}
			}
		}
	case common.RoleStandby:
		// We are a standby
		followedUID := db.Spec.FollowConfig.DBUID
		log.Info("our db requested role is standby", zap.String("followedDB", followedUID))
		followedDB, ok := cd.DBs[followedUID]
		if !ok {
			log.Error("no db data available for followed db", zap.String("followedDB", followedUID))
			return
		}
		switch localRole {
		case common.RoleMaster:
			if systemID == followedDB.Status.SystemID {
				// There can be the possibility that this
				// database is on the same branch of the
				// current followed instance.
				// So we try to put it in recovery and then
				// check if it's on the same branch or force a
				// resync
				replConnParams := p.getReplConnParams(db, followedDB)
				standbySettings := &cluster.StandbySettings{PrimaryConninfo: replConnParams.ConnString(), PrimarySlotName: common.StolonName(db.UID)}
				if err = pgm.WriteRecoveryConf(p.createRecoveryParameters(standbySettings, nil)); err != nil {
					log.Error("err", zap.Error(err))
					return
				}
				if !started {
					if err = pgm.Start(); err != nil {
						log.Error("err", zap.Error(err))
						return
					}
					started = true
				} else {
					if err = pgm.Restart(true); err != nil {
						log.Error("err", zap.Error(err))
						return
					}
				}

				// TODO(sgotti) pg_rewind considers databases on the same timeline as in sync and doesn't check if they diverged at different position in previous timelines.
				// So check that the db as been synced or resync again with pg_rewind disabled. Will need to report this upstream.

				// Check timeline history
				// We need to update our pgState to avoid dealing with
				// an old pgState not reflecting the real state
				var pgState *cluster.PostgresState
				pgState, err = p.GetPGState(pctx)
				if err != nil {
					log.Error("cannot get current pgstate", zap.Error(err))
					return
				}

				if p.isDifferentTimelineBranch(followedDB, pgState) {
					if err = p.resync(db, followedDB, true, started); err != nil {
						log.Error("failed to resync from followed instance", zap.Error(err))
						return
					}
					if err = pgm.Start(); err != nil {
						log.Error("err", zap.Error(err))
						return
					}
					started = true

					// Check again if it was really synced
					pgState, err = p.GetPGState(pctx)
					if err != nil {
						log.Error("cannot get current pgstate", zap.Error(err))
						return
					}
					if p.isDifferentTimelineBranch(followedDB, pgState) {
						if err = p.resync(db, followedDB, false, started); err != nil {
							log.Error("failed to resync from followed instance", zap.Error(err))
							return
						}
						if err = pgm.Start(); err != nil {
							log.Error("err", zap.Error(err))
							return
						}
						started = true
					}
				}
			} else {
				if err = p.resync(db, followedDB, false, started); err != nil {
					log.Error("failed to resync from followed instance", zap.Error(err))
					return
				}
				if err = pgm.Start(); err != nil {
					log.Error("err", zap.Error(err))
					return
				}
				started = true
			}
		case common.RoleStandby:
			log.Info("already standby")
			if !started {
				replConnParams := p.getReplConnParams(db, followedDB)
				standbySettings := &cluster.StandbySettings{PrimaryConninfo: replConnParams.ConnString(), PrimarySlotName: common.StolonName(db.UID)}
				if err = pgm.WriteRecoveryConf(p.createRecoveryParameters(standbySettings, nil)); err != nil {
					log.Error("err", zap.Error(err))
					return
				}
				if err = pgm.Start(); err != nil {
					log.Error("failed to start postgres", zap.Error(err))
					return
				}
				started = true
			}

			// Check that we can sync with followed instance

			// We need to update our pgState to avoid dealing with
			// an old pgState not reflecting the real state
			var pgState *cluster.PostgresState
			pgState, err = p.GetPGState(pctx)
			if err != nil {
				log.Error("cannot get current pgstate", zap.Error(err))
				return
			}
			needsResync := false
			tryPgrewind := false
			// If the db has a different systemdID then a resync is needed
			if systemID != followedDB.Status.SystemID {
				needsResync = true
				// Check timeline history
			} else if p.isDifferentTimelineBranch(followedDB, pgState) {
				needsResync = true
				tryPgrewind = true
			}
			if needsResync {
				// TODO(sgotti) pg_rewind considers databases on the same timeline as in sync and doesn't check if they diverged at different position in previous timelines.
				// So check that the db as been synced or resync again with pg_rewind disabled. Will need to report this upstream.
				if err = p.resync(db, followedDB, tryPgrewind, started); err != nil {
					log.Error("failed to full resync from followed instance", zap.Error(err))
					return
				}
				if err = pgm.Start(); err != nil {
					log.Error("err", zap.Error(err))
					return
				}
				started = true

				// Check again if it was really synced
				pgState, err = p.GetPGState(pctx)
				if err != nil {
					log.Error("cannot get current pgstate", zap.Error(err))
					return
				}
				if p.isDifferentTimelineBranch(followedDB, pgState) {
					if err = p.resync(db, followedDB, false, started); err != nil {
						log.Error("failed to resync from followed instance", zap.Error(err))
						return
					}
					if err = pgm.Start(); err != nil {
						log.Error("err", zap.Error(err))
						return
					}
					started = true
				}
			}

			// TODO(sgotti) Check that the followed instance has all the needed WAL segments

			// Update our primary_conninfo if replConnString changed
			var curReplConnParams postgresql.ConnParams

			curReplConnParams, err = pgm.GetPrimaryConninfo()
			if err != nil {
				log.Error("err", zap.Error(err))
				return
			}
			log.Debug("curReplConnParams", zap.Object("curReplConnParams", curReplConnParams))

			newReplConnParams := p.getReplConnParams(db, followedDB)
			log.Debug("newReplConnParams", zap.Object("newReplConnParams", newReplConnParams))

			if !curReplConnParams.Equals(newReplConnParams) {
				log.Info("connection parameters changed. Reconfiguring.", zap.String("followedDB", followedUID), zap.Object("replConnParams", newReplConnParams))
				standbySettings := &cluster.StandbySettings{PrimaryConninfo: newReplConnParams.ConnString(), PrimarySlotName: common.StolonName(db.UID)}
				if err = pgm.WriteRecoveryConf(p.createRecoveryParameters(standbySettings, nil)); err != nil {
					log.Error("err", zap.Error(err))
					return
				}
				if err = pgm.Restart(true); err != nil {
					log.Error("err", zap.Error(err))
					return
				}
			}
		case common.RoleUndefined:
			if err = p.resync(db, followedDB, false, started); err != nil {
				log.Error("failed to full resync from followed instance", zap.Error(err))
				return
			}
			if err = pgm.Start(); err != nil {
				log.Error("err", zap.Error(err))
				return
			}
			started = true
		}
	case common.RoleUndefined:
		log.Info("our db requested role is none")
		return
	}

	// update pg parameters
	pgParameters = p.createPGParameters(db)

	// Log synchronous replication changes
	prevSyncStandbyNames := prevPGParameters["synchronous_standby_names"]
	syncStandbyNames := pgParameters["synchronous_standby_names"]
	if db.Spec.SynchronousReplication {
		if prevSyncStandbyNames != syncStandbyNames {
			log.Info("needed synchronous_standby_names changed", zap.String("prevSyncStandbyNames", prevSyncStandbyNames), zap.String("syncStandbyNames", syncStandbyNames))
		}
	} else {
		if prevSyncStandbyNames != "" {
			log.Info("sync replication disabled, removing current synchronous_standby_names", zap.String("syncStandbyNames", prevSyncStandbyNames))
		}
	}

	if !pgParameters.Equals(prevPGParameters) {
		log.Info("postgres parameters changed, reloading postgres instance")
		pgm.SetParameters(pgParameters)
		if err := pgm.Reload(); err != nil {
			log.Error("failed to reload postgres instance", zap.Error(err))
		}
	} else {
		// for tests
		log.Info("postgres parameters not changed")
	}

	// If we are here, then all went well and we can update the db generation and save it locally
	p.localStateMutex.Lock()
	dbls.Generation = db.Generation
	dbls.Initializing = false
	p.localStateMutex.Unlock()
	if err := p.saveDBLocalState(); err != nil {
		log.Error("err", zap.Error(err))
		return
	}
}
Example #5
0
func (p *PostgresKeeper) resync(db, followedDB *cluster.DB, tryPgrewind, started bool) error {
	pgm := p.pgm
	if started {
		if err := pgm.Stop(true); err != nil {
			return fmt.Errorf("failed to stop pg instance: %v", err)
		}
	}
	replConnParams := p.getReplConnParams(db, followedDB)
	standbySettings := &cluster.StandbySettings{PrimaryConninfo: replConnParams.ConnString(), PrimarySlotName: common.StolonName(db.UID)}

	// TODO(sgotti) Actually we don't check if pg_rewind is installed or if
	// postgresql version is > 9.5 since someone can also use an externally
	// installed pg_rewind for postgres 9.4. If a pg_rewind executable
	// doesn't exists pgm.SyncFromFollowedPGRewind will return an error and
	// fallback to pg_basebackup
	if tryPgrewind && p.usePgrewind(db) {
		connParams := p.getSUConnParams(db, followedDB)
		log.Info("syncing using pg_rewind", zap.String("followedDB", followedDB.UID), zap.String("keeper", followedDB.Spec.KeeperUID))
		if err := pgm.SyncFromFollowedPGRewind(connParams, p.pgSUPassword); err != nil {
			// log pg_rewind error and fallback to pg_basebackup
			log.Error("error syncing with pg_rewind", zap.Error(err))
		} else {
			if err := pgm.WriteRecoveryConf(p.createRecoveryParameters(standbySettings, nil)); err != nil {
				return fmt.Errorf("err: %v", err)
			}
			return nil
		}
	}

	if err := pgm.RemoveAll(); err != nil {
		return fmt.Errorf("failed to remove the postgres data dir: %v", err)
	}
	if log.Level() >= zap.DebugLevel {
		log.Debug("syncing from followed db", zap.String("followedDB", followedDB.UID), zap.String("keeper", followedDB.Spec.KeeperUID), zap.String("replConnParams", fmt.Sprintf("%v", replConnParams)))
	} else {
		log.Info("syncing from followed db", zap.String("followedDB", followedDB.UID), zap.String("keeper", followedDB.Spec.KeeperUID))
	}
	if err := pgm.SyncFromFollowed(replConnParams); err != nil {
		return fmt.Errorf("sync error: %v", err)
	}
	log.Info("sync succeeded")

	if err := pgm.WriteRecoveryConf(p.createRecoveryParameters(standbySettings, nil)); err != nil {
		return fmt.Errorf("err: %v", err)
	}
	return nil
}