reparent.go

// Copyright 2013, Google Inc. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package vtctl

import (
	"flag"
	"fmt"
	"time"

	"github.com/youtube/vitess/go/vt/servenv"
	"github.com/youtube/vitess/go/vt/topo/topoproto"
	"github.com/youtube/vitess/go/vt/wrangler"
	"golang.org/x/net/context"

	topodatapb "github.com/youtube/vitess/go/vt/proto/topodata"
)

var (
	// DisableActiveReparents is a flag to disable active
	// reparents for safety reasons. It is used in two places:
	// 1. in this file to skip registering the commands.
	// 2. in vtctld so it can be exported to the UI (different
	// package, that's why it's exported). That way we can disable
	// menu items there, using features.
	DisableActiveReparents = flag.Bool("disable_active_reparents", false, "if set, do not allow active reparents. Use this to protect a cluster using external reparents.")
)

func init() {
	servenv.OnRun(func() {
		if *DisableActiveReparents {
			return
		}

		addCommand("Tablets", command{
			"ReparentTablet",
			commandReparentTablet,
			"<tablet alias>",
			"Reparent a tablet to the current master in the shard. This only works if the current slave position matches the last known reparent action."})

		addCommand("Shards", command{
			"InitShardMaster",
			commandInitShardMaster,
			"[-force] [-wait_slave_timeout=<duration>] <keyspace/shard> <tablet alias>",
			"Sets the initial master for a shard. Will make all other tablets in the shard slaves of the provided master. WARNING: this could cause data loss on an already replicating shard. PlannedReparentShard or EmergencyReparentShard should be used instead."})
		addCommand("Shards", command{
			"PlannedReparentShard",
			commandPlannedReparentShard,
			"-keyspace_shard=<keyspace/shard> [-new_master=<tablet alias>] [-avoid_master=<tablet alias>]",
			"Reparents the shard to the new master, or away from old master. Both old and new master need to be up and running."})
		addCommand("Shards", command{
			"EmergencyReparentShard",
			commandEmergencyReparentShard,
			"-keyspace_shard=<keyspace/shard> -new_master=<tablet alias>",
			"Reparents the shard to the new master. Assumes the old master is dead and not responsding."})
	})
}

func commandReparentTablet(ctx context.Context, wr *wrangler.Wrangler, subFlags *flag.FlagSet, args []string) error {
	if err := subFlags.Parse(args); err != nil {
		return err
	}
	if subFlags.NArg() != 1 {
		return fmt.Errorf("action ReparentTablet requires <tablet alias>")
	}
	tabletAlias, err := topoproto.ParseTabletAlias(subFlags.Arg(0))
	if err != nil {
		return err
	}
	return wr.ReparentTablet(ctx, tabletAlias)
}

func commandInitShardMaster(ctx context.Context, wr *wrangler.Wrangler, subFlags *flag.FlagSet, args []string) error {
	force := subFlags.Bool("force", false, "will force the reparent even if the provided tablet is not a master or the shard master")
	waitSlaveTimeout := subFlags.Duration("wait_slave_timeout", 30*time.Second, "time to wait for slaves to catch up in reparenting")
	if err := subFlags.Parse(args); err != nil {
		return err
	}
	if subFlags.NArg() != 2 {
		return fmt.Errorf("action InitShardMaster requires <keyspace/shard> <tablet alias>")
	}
	keyspace, shard, err := topoproto.ParseKeyspaceShard(subFlags.Arg(0))
	if err != nil {
		return err
	}
	tabletAlias, err := topoproto.ParseTabletAlias(subFlags.Arg(1))
	if err != nil {
		return err
	}
	return wr.InitShardMaster(ctx, keyspace, shard, tabletAlias, *force, *waitSlaveTimeout)
}

func commandPlannedReparentShard(ctx context.Context, wr *wrangler.Wrangler, subFlags *flag.FlagSet, args []string) error {
	waitSlaveTimeout := subFlags.Duration("wait_slave_timeout", 30*time.Second, "time to wait for slaves to catch up in reparenting")
	keyspaceShard := subFlags.String("keyspace_shard", "", "keyspace/shard of the shard that needs to be reparented")
	newMaster := subFlags.String("new_master", "", "alias of a tablet that should be the new master")
	avoidMaster := subFlags.String("avoid_master", "", "alias of a tablet that should not be the master, i.e. reparent to any other tablet if this one is the master")
	if err := subFlags.Parse(args); err != nil {
		return err
	}
	if subFlags.NArg() == 2 {
		// Legacy syntax: "<keyspace/shard> <tablet alias>".
		if *keyspaceShard != "" || *newMaster != "" {
			return fmt.Errorf("cannot use legacy syntax and flags -keyspace_shard and -new_master for action PlannedReparentShard at the same time")
		}
		*keyspaceShard = subFlags.Arg(0)
		*newMaster = subFlags.Arg(1)
	} else if subFlags.NArg() != 0 {
		return fmt.Errorf("action PlannedReparentShard requires -keyspace_shard=<keyspace/shard> [-new_master=<tablet alias>] [-avoid_master=<tablet alias>]")
	}

	keyspace, shard, err := topoproto.ParseKeyspaceShard(*keyspaceShard)
	if err != nil {
		return err
	}
	var newMasterAlias, avoidMasterAlias *topodatapb.TabletAlias
	if *newMaster != "" {
		newMasterAlias, err = topoproto.ParseTabletAlias(*newMaster)
		if err != nil {
			return err
		}
	}
	if *avoidMaster != "" {
		avoidMasterAlias, err = topoproto.ParseTabletAlias(*avoidMaster)
		if err != nil {
			return err
		}
	}
	return wr.PlannedReparentShard(ctx, keyspace, shard, newMasterAlias, avoidMasterAlias, *waitSlaveTimeout)
}

func commandEmergencyReparentShard(ctx context.Context, wr *wrangler.Wrangler, subFlags *flag.FlagSet, args []string) error {
	waitSlaveTimeout := subFlags.Duration("wait_slave_timeout", 30*time.Second, "time to wait for slaves to catch up in reparenting")
	keyspaceShard := subFlags.String("keyspace_shard", "", "keyspace/shard of the shard that needs to be reparented")
	newMaster := subFlags.String("new_master", "", "alias of a tablet that should be the new master")
	if err := subFlags.Parse(args); err != nil {
		return err
	}
	if subFlags.NArg() == 2 {
		// Legacy syntax: "<keyspace/shard> <tablet alias>".
		if *newMaster != "" {
			return fmt.Errorf("cannot use legacy syntax and flag -new_master for action EmergencyReparentShard at the same time")
		}
		*keyspaceShard = subFlags.Arg(0)
		*newMaster = subFlags.Arg(1)
	} else if subFlags.NArg() != 0 {
		return fmt.Errorf("action EmergencyReparentShard requires -keyspace_shard=<keyspace/shard> -new_master=<tablet alias>")
	}

	keyspace, shard, err := topoproto.ParseKeyspaceShard(*keyspaceShard)
	if err != nil {
		return err
	}
	tabletAlias, err := topoproto.ParseTabletAlias(*newMaster)
	if err != nil {
		return err
	}
	return wr.EmergencyReparentShard(ctx, keyspace, shard, tabletAlias, *waitSlaveTimeout)
}