gh-ost/go/cmd/gh-ost/main.go

/*
   Copyright 2016 GitHub Inc.
	 See https://github.com/github/gh-ost/blob/master/LICENSE
*/

package main

import (
	"flag"
	"fmt"
	"os"
	"os/signal"
	"syscall"

	"github.com/github/gh-ost/go/base"
	"github.com/github/gh-ost/go/logic"
	"github.com/outbrain/golib/log"
)

var AppVersion string

// acceptSignals registers for OS signals
func acceptSignals(migrationContext *base.MigrationContext) {
	c := make(chan os.Signal, 1)

	signal.Notify(c, syscall.SIGHUP)
	go func() {
		for sig := range c {
			switch sig {
			case syscall.SIGHUP:
				log.Infof("Received SIGHUP. Reloading configuration")
				if err := migrationContext.ReadConfigFile(); err != nil {
					log.Errore(err)
				} else {
					migrationContext.MarkPointOfInterest()
				}
			}
		}
	}()
}

// main is the application's entry point. It will either spawn a CLI or HTTP itnerfaces.
func main() {
	migrationContext := base.GetMigrationContext()

	flag.StringVar(&migrationContext.InspectorConnectionConfig.Key.Hostname, "host", "127.0.0.1", "MySQL hostname (preferably a replica, not the master)")
	flag.IntVar(&migrationContext.InspectorConnectionConfig.Key.Port, "port", 3306, "MySQL port (preferably a replica, not the master)")
	flag.StringVar(&migrationContext.CliUser, "user", "", "MySQL user")
	flag.StringVar(&migrationContext.CliPassword, "password", "", "MySQL password")
	flag.StringVar(&migrationContext.ConfigFile, "conf", "", "Config file")

	flag.StringVar(&migrationContext.DatabaseName, "database", "", "database name (mandatory)")
	flag.StringVar(&migrationContext.OriginalTableName, "table", "", "table name (mandatory)")
	flag.StringVar(&migrationContext.AlterStatement, "alter", "", "alter statement (mandatory)")
	flag.BoolVar(&migrationContext.CountTableRows, "exact-rowcount", false, "actually count table rows as opposed to estimate them (results in more accurate progress estimation)")
	flag.BoolVar(&migrationContext.AllowedRunningOnMaster, "allow-on-master", false, "allow this migration to run directly on master. Preferably it would run on a replica")
	flag.BoolVar(&migrationContext.NullableUniqueKeyAllowed, "allow-nullable-unique-key", false, "allow gh-ost to migrate based on a unique key with nullable columns. As long as no NULL values exist, this should be OK. If NULL values exist in chosen key, data may be corrupted. Use at your own risk!")
	flag.BoolVar(&migrationContext.ApproveRenamedColumns, "approve-renamed-columns", false, "in case your `ALTER` statement renames columns, gh-ost will note that and offer its interpretation of the rename. By default gh-ost does not proceed to execute. This flag approves that gh-ost's interpretation si correct")
	flag.BoolVar(&migrationContext.SkipRenamedColumns, "skip-renamed-columns", false, "in case your `ALTER` statement renames columns, gh-ost will note that and offer its interpretation of the rename. By default gh-ost does not proceed to execute. This flag tells gh-ost to skip the renamed columns, i.e. to treat what gh-ost thinks are renamed columns as unrelated columns. NOTE: you may lose column data")

	executeFlag := flag.Bool("execute", false, "actually execute the alter & migrate the table. Default is noop: do some tests and exit")
	flag.BoolVar(&migrationContext.TestOnReplica, "test-on-replica", false, "Have the migration run on a replica, not on the master. At the end of migration replication is stopped, and tables are swapped and immediately swap-revert. Replication remains stopped and you can compare the two tables for building trust")
	flag.BoolVar(&migrationContext.MigrateOnReplica, "migrate-on-replica", false, "Have the migration run on a replica, not on the master. This will do the full migration on the replica including cut-over (as opposed to --test-on-replica)")

	flag.BoolVar(&migrationContext.OkToDropTable, "ok-to-drop-table", false, "Shall the tool drop the old table at end of operation. DROPping tables can be a long locking operation, which is why I'm not doing it by default. I'm an online tool, yes?")
	flag.BoolVar(&migrationContext.InitiallyDropOldTable, "initially-drop-old-table", false, "Drop a possibly existing OLD table (remains from a previous run?) before beginning operation. Default is to panic and abort if such table exists")
	flag.BoolVar(&migrationContext.InitiallyDropGhostTable, "initially-drop-ghost-table", false, "Drop a possibly existing Ghost table (remains from a previous run?) before beginning operation. Default is to panic and abort if such table exists")
	cutOver := flag.String("cut-over", "", "(mandatory) choose cut-over type (two-step, voluntary-lock)")

	flag.BoolVar(&migrationContext.SwitchToRowBinlogFormat, "switch-to-rbr", false, "let this tool automatically switch binary log format to 'ROW' on the replica, if needed. The format will NOT be switched back. I'm too scared to do that, and wish to protect you if you happen to execute another migration while this one is running")
	chunkSize := flag.Int64("chunk-size", 1000, "amount of rows to handle in each iteration (allowed range: 100-100,000)")

	flag.Int64Var(&migrationContext.MaxLagMillisecondsThrottleThreshold, "max-lag-millis", 1500, "replication lag at which to throttle operation")
	flag.StringVar(&migrationContext.ReplictionLagQuery, "replication-lag-query", "", "Query that detects replication lag in seconds. Result can be a floating point (by default gh-ost issues SHOW SLAVE STATUS and reads Seconds_behind_master). If you're using pt-heartbeat, query would be something like: SELECT ROUND(UNIX_TIMESTAMP() - MAX(UNIX_TIMESTAMP(ts))) AS delay FROM my_schema.heartbeat")
	throttleControlReplicas := flag.String("throttle-control-replicas", "", "List of replicas on which to check for lag; comma delimited. Example: myhost1.com:3306,myhost2.com,myhost3.com:3307")
	flag.StringVar(&migrationContext.ThrottleFlagFile, "throttle-flag-file", "", "operation pauses when this file exists; hint: use a file that is specific to the table being altered")
	flag.StringVar(&migrationContext.ThrottleAdditionalFlagFile, "throttle-additional-flag-file", "/tmp/gh-ost.throttle", "operation pauses when this file exists; hint: keep default, use for throttling multiple gh-ost operations")
	flag.StringVar(&migrationContext.PostponeCutOverFlagFile, "postpone-cut-over-flag-file", "", "while this file exists, migration will postpone the final stage of swapping tables, and will keep on syncing the ghost table. Cut-over/swapping would be ready to perform the moment the file is deleted.")

	flag.StringVar(&migrationContext.ServeSocketFile, "serve-socket-file", "", "Unix socket file to serve on. Default: auto-determined and advertised upon startup")
	flag.Int64Var(&migrationContext.ServeTCPPort, "serve-tcp-port", 0, "TCP port to serve on. Default: disabled")

	maxLoad := flag.String("max-load", "", "Comma delimited status-name=threshold. e.g: 'Threads_running=100,Threads_connected=500'")
	quiet := flag.Bool("quiet", false, "quiet")
	verbose := flag.Bool("verbose", false, "verbose")
	debug := flag.Bool("debug", false, "debug mode (very verbose)")
	stack := flag.Bool("stack", false, "add stack trace upon error")
	help := flag.Bool("help", false, "Display usage")
	version := flag.Bool("version", false, "Print version & exit")
	flag.Parse()

	if *help {
		fmt.Fprintf(os.Stderr, "Usage of gh-ost:\n")
		flag.PrintDefaults()
		return
	}
	if *version {
		appVersion := AppVersion
		if appVersion == "" {
			appVersion = "unversioned"
		}
		fmt.Println(appVersion)
		return
	}

	log.SetLevel(log.ERROR)
	if *verbose {
		log.SetLevel(log.INFO)
	}
	if *debug {
		log.SetLevel(log.DEBUG)
	}
	if *stack {
		log.SetPrintStackTrace(*stack)
	}
	if *quiet {
		// Override!!
		log.SetLevel(log.ERROR)
	}

	if migrationContext.DatabaseName == "" {
		log.Fatalf("--database must be provided and database name must not be empty")
	}
	if migrationContext.OriginalTableName == "" {
		log.Fatalf("--table must be provided and table name must not be empty")
	}
	if migrationContext.AlterStatement == "" {
		log.Fatalf("--alter must be provided and statement must not be empty")
	}
	migrationContext.Noop = !(*executeFlag)
	if migrationContext.AllowedRunningOnMaster && migrationContext.TestOnReplica {
		log.Fatalf("--allow-on-master and --test-on-replica are mutually exclusive")
	}
	if migrationContext.AllowedRunningOnMaster && migrationContext.MigrateOnReplica {
		log.Fatalf("--allow-on-master and --migrate-on-replica are mutually exclusive")
	}
	if migrationContext.MigrateOnReplica && migrationContext.TestOnReplica {
		log.Fatalf("--migrate-on-replica and --test-on-replica are mutually exclusive")
	}

	switch *cutOver {
	case "safe", "default", "":
		migrationContext.CutOverType = base.CutOverSafe
	case "two-step":
		migrationContext.CutOverType = base.CutOverTwoStep
	default:
		log.Fatalf("Unknown cut-over: %s", *cutOver)
	}
	if err := migrationContext.ReadConfigFile(); err != nil {
		log.Fatale(err)
	}
	if err := migrationContext.ThrottleControlReplicaKeys.ReadCommaDelimitedList(*throttleControlReplicas); err != nil {
		log.Fatale(err)
	}
	if err := migrationContext.ReadMaxLoad(*maxLoad); err != nil {
		log.Fatale(err)
	}
	if migrationContext.ServeSocketFile == "" {
		migrationContext.ServeSocketFile = fmt.Sprintf("/tmp/gh-ost.%s.%s.sock", migrationContext.DatabaseName, migrationContext.OriginalTableName)
	}
	migrationContext.SetChunkSize(*chunkSize)
	migrationContext.ApplyCredentials()

	log.Infof("starting gh-ost %+v", AppVersion)
	acceptSignals(migrationContext)

	migrator := logic.NewMigrator()
	err := migrator.Migrate()
	if err != nil {
		log.Fatale(err)
	}
	log.Info("Done")
}