Candidate databse instance: database native time

go/app/cli.go

@@ -1456,7 +1456,7 @@ func Cli(command string, strict bool, instance string, destination string, owner
 			if err != nil {
 				log.Fatale(err)
 			}
-			err = inst.RegisterCandidateInstance(inst.NewCandidateDatabaseInstance(instanceKey, promotionRule))
+			err = inst.RegisterCandidateInstance(inst.NewCandidateDatabaseInstance(instanceKey, promotionRule).WithCurrentTime())
 			if err != nil {
 				log.Fatale(err)
 			}

go/db/db.go

@@ -394,3 +394,15 @@ func QueryOrchestratorBuffered(query string, argsArray []interface{}, on_row fun
 	}
 	return log.Criticale(sqlutils.QueryRowsMapBuffered(db, query, on_row, argsArray...))
 }
+
+// ReadTimeNow reads and returns the current timestamp as string. This is an unfortunate workaround
+// to support both MySQL and SQLite in all possible timezones. SQLite only speaks UTC where MySQL has
+// timezone support. By reading the time as string we get the database's de-facto notion of the time,
+// which we can then feed back to it.
+func ReadTimeNow() (timeNow string, err error) {
+	err = QueryOrchestrator(`select now() as time_now`, nil, func(m sqlutils.RowMap) error {
+		timeNow = m.GetString("time_now")
+		return nil
+	})
+	return timeNow, err
+}

go/http/api.go

@@ -2853,7 +2853,7 @@ func (this *HttpAPI) RegisterCandidate(params martini.Params, r render.Render, r
 		return
 	}
 
-	candidate := inst.NewCandidateDatabaseInstance(&instanceKey, promotionRule)
+	candidate := inst.NewCandidateDatabaseInstance(&instanceKey, promotionRule).WithCurrentTime()
 
 	if orcraft.IsRaftEnabled() {
 		_, err = orcraft.PublishCommand("register-candidate", candidate)

go/inst/candidate_database_instance.go

@@ -18,26 +18,31 @@ package inst
 
 import (
 	"fmt"
-	"time"
+
+	"github.com/github/orchestrator/go/db"
 )
 
 // CandidateDatabaseInstance contains information about explicit promotion rules for an instance
 type CandidateDatabaseInstance struct {
-	Hostname      string
-	Port          int
-	PromotionRule CandidatePromotionRule
-	LastSuggested time.Time
+	Hostname            string
+	Port                int
+	PromotionRule       CandidatePromotionRule
+	LastSuggestedString string
 }
 
 func NewCandidateDatabaseInstance(instanceKey *InstanceKey, promotionRule CandidatePromotionRule) *CandidateDatabaseInstance {
 	return &CandidateDatabaseInstance{
 		Hostname:      instanceKey.Hostname,
 		Port:          instanceKey.Port,
 		PromotionRule: promotionRule,
-		LastSuggested: time.Now(),
 	}
 }
 
+func (cdi *CandidateDatabaseInstance) WithCurrentTime() *CandidateDatabaseInstance {
+	cdi.LastSuggestedString, _ = db.ReadTimeNow()
+	return cdi
+}
+
 // String returns a string representation of the CandidateDatabaseInstance struct
 func (cdi *CandidateDatabaseInstance) String() string {
 	return fmt.Sprintf("%s:%d %s", cdi.Hostname, cdi.Port, cdi.PromotionRule)

go/inst/candidate_database_instance_dao.go

@@ -17,11 +17,55 @@
 package inst
 
 import (
+	"fmt"
+
+	"github.com/openark/golib/log"
 	"github.com/openark/golib/sqlutils"
 
+	"github.com/github/orchestrator/go/config"
 	"github.com/github/orchestrator/go/db"
 )
 
+// RegisterCandidateInstance markes a given instance as suggested for successoring a master in the event of failover.
+func RegisterCandidateInstance(candidate *CandidateDatabaseInstance) error {
+	if candidate.LastSuggestedString == "" {
+		candidate = candidate.WithCurrentTime()
+	}
+	args := sqlutils.Args(candidate.Hostname, candidate.Port, string(candidate.PromotionRule), candidate.LastSuggestedString)
+
+	query := fmt.Sprintf(`
+			insert into candidate_database_instance (
+					hostname,
+					port,
+					promotion_rule,
+					last_suggested
+				) values (
+					?, ?, ?, ?
+				) on duplicate key update
+					last_suggested=values(last_suggested),
+					promotion_rule=values(promotion_rule)
+			`)
+	writeFunc := func() error {
+		_, err := db.ExecOrchestrator(query, args...)
+		AuditOperation("register-candidate", candidate.Key(), string(candidate.PromotionRule))
+		return log.Errore(err)
+	}
+	return ExecDBWriteFunc(writeFunc)
+}
+
+// ExpireCandidateInstances removes stale master candidate suggestions.
+func ExpireCandidateInstances() error {
+	writeFunc := func() error {
+		_, err := db.ExecOrchestrator(`
+				delete from candidate_database_instance
+				where last_suggested < NOW() - INTERVAL ? MINUTE
+				`, config.Config.CandidateInstanceExpireMinutes,
+		)
+		return log.Errore(err)
+	}
+	return ExecDBWriteFunc(writeFunc)
+}
+
 // BulkReadCandidateDatabaseInstance returns a slice of
 // CandidateDatabaseInstance converted to JSON.
 /*
@@ -49,10 +93,10 @@ func BulkReadCandidateDatabaseInstance() ([]CandidateDatabaseInstance, error) {
 	`
 	err := db.QueryOrchestrator(query, nil, func(m sqlutils.RowMap) error {
 		cdi := CandidateDatabaseInstance{
-			Hostname:      m.GetString("hostname"),
-			Port:          m.GetInt("port"),
-			PromotionRule: CandidatePromotionRule(m.GetString("promotion_rule")),
-			LastSuggested: m.GetTime("last_suggested"),
+			Hostname:            m.GetString("hostname"),
+			Port:                m.GetInt("port"),
+			PromotionRule:       CandidatePromotionRule(m.GetString("promotion_rule")),
+			LastSuggestedString: m.GetString("last_suggested"),
 		}
 		// add to end of candidateDatabaseInstances
 		candidateDatabaseInstances = append(candidateDatabaseInstances, cdi)

go/inst/instance_dao.go

@@ -723,7 +723,7 @@ func ReadTopologyInstanceBufferable(instanceKey *InstanceKey, bufferWrites bool,
 				// We register the rule even if it hasn't changed,
 				// to bump the last_suggested time.
 				instance.PromotionRule = promotionRule
-				err = RegisterCandidateInstance(NewCandidateDatabaseInstance(instanceKey, promotionRule))
+				err = RegisterCandidateInstance(NewCandidateDatabaseInstance(instanceKey, promotionRule).WithCurrentTime())
 				logReadTopologyInstanceError(instanceKey, "RegisterCandidateInstance", err)
 			}
 		}()
@@ -2550,52 +2550,6 @@ func ReadHistoryClusterInstances(clusterName string, historyTimestampPattern str
 	return instances, err
 }
 
-// RegisterCandidateInstance markes a given instance as suggested for successoring a master in the event of failover.
-func RegisterCandidateInstance(candidate *CandidateDatabaseInstance) error {
-	args := sqlutils.Args(candidate.Hostname, candidate.Port, string(candidate.PromotionRule))
-	lastSuggestedHint := "now()"
-	if !candidate.LastSuggested.IsZero() {
-		lastSuggestedHint = "?"
-		args = append(args, candidate.LastSuggested)
-	}
-	query := fmt.Sprintf(`
-			insert into candidate_database_instance (
-					hostname,
-					port,
-					promotion_rule,
-					last_suggested
-				) values (?, ?, ?, %s)
-				on duplicate key update
-					hostname=values(hostname),
-					port=values(port),
-					last_suggested=now(),
-					promotion_rule=values(promotion_rule)
-			`, lastSuggestedHint)
-	writeFunc := func() error {
-		_, err := db.ExecOrchestrator(query, args...)
-		AuditOperation("register-candidate", candidate.Key(), string(candidate.PromotionRule))
-		return log.Errore(err)
-	}
-	return ExecDBWriteFunc(writeFunc)
-}
-
-// ExpireCandidateInstances removes stale master candidate suggestions.
-func ExpireCandidateInstances() error {
-	writeFunc := func() error {
-		_, err := db.ExecOrchestrator(`
-        	delete from candidate_database_instance
-				where last_suggested < NOW() - INTERVAL ? MINUTE
-				`, config.Config.CandidateInstanceExpireMinutes,
-		)
-		if err != nil {
-			return log.Errore(err)
-		}
-
-		return nil
-	}
-	return ExecDBWriteFunc(writeFunc)
-}
-
 // RecordInstanceCoordinatesHistory snapshots the binlog coordinates of instances
 func RecordInstanceCoordinatesHistory() error {
 	{