Optionally allow turning psync-able replicas to new master before pro…

…mote

.github/workflows/golangci-lint.yml

@@ -24,4 +24,4 @@ jobs:
       - name: golangci-lint
         uses: golangci/golangci-lint-action@v6
         with:
-          version: v1.55
+          version: v1.58

Makefile

@@ -10,7 +10,7 @@ format:
 	goimports -w `find . -name '*.go'`
 
 lint:
-	docker run --rm -v ${CURDIR}:/app -w /app golangci/golangci-lint:v1.55-alpine golangci-lint run -v
+	docker run --rm -v ${CURDIR}:/app -w /app golangci/golangci-lint:v1.58-alpine golangci-lint run -v
 
 unittests:
 	go test ./cmd/... ./internal/...

internal/app/switchover.go

@@ -354,6 +354,33 @@ func (app *App) performSwitchover(shardState map[string]*HostState, activeNodes
 			app.waitPoisonPill(app.config.Redis.WaitPoisonPillTimeout)
 		}
 
+		if app.config.Redis.TurnBeforeSwitchover {
+			var psyncNodes []string
+			for _, host := range aliveActiveNodes {
+				if host == newMaster {
+					continue
+				}
+				if isPartialSyncPossible(shardState[host], shardState[newMaster]) {
+					psyncNodes = append(psyncNodes, host)
+				}
+			}
+
+			errs := runParallel(func(host string) error {
+				if !shardState[host].PingOk {
+					return nil
+				}
+				err := app.changeMaster(host, newMaster)
+				if err != nil {
+					return err
+				}
+				return nil
+			}, psyncNodes)
+
+			err := combineErrors(errs)
+			if err != nil {
+				app.logger.Warn("Unable to psync some replicas before promote", "error", err)
+			}
+		}
 		deadline := time.Now().Add(app.config.Redis.WaitPromoteTimeout)
 		forceDeadline := time.Now().Add(app.config.Redis.WaitPromoteForceTimeout)
 		promoted := false

internal/config/config.go

@@ -35,6 +35,7 @@ type RedisConfig struct {
 	MaxParallelSyncs        int           `yaml:"max_parallel_syncs"`
 	MaxReplicasToWrite      int           `yaml:"max_replicas_to_write"`
 	AllowDataLoss           bool          `yaml:"allow_data_loss"`
+	TurnBeforeSwitchover    bool          `yaml:"turn_before_switchover"`
 	RestartCommand          string        `yaml:"restart_command"`
 }
 
@@ -108,6 +109,7 @@ func DefaultRedisConfig() RedisConfig {
 		MaxParallelSyncs:        1,
 		MaxReplicasToWrite:      -1,
 		AllowDataLoss:           false,
+		TurnBeforeSwitchover:    false,
 		RestartCommand:          "systemctl restart redis-server",
 	}
 }