onlineddl

Documentation

Overview

Package heartbeat contains a writer and reader of heartbeats for a master-replica cluster. This is similar to Percona's pt-heartbeat, and is meant to supplement the information returned from SHOW SLAVE STATUS. In some circumstances, lag returned from SHOW SLAVE STATUS is incorrect and is at best only at 1 second resolution. The heartbeat package directly tests replication by writing a record with a timestamp on the master, and comparing that timestamp after reading it on the replica. This happens at the interval defined by heartbeat_interval. Note: the lag reported will be affected by clock drift, so it is recommended to run ntpd or similar.

The data collected by the heartbeat package is made available in /debug/vars in counters prefixed by Heartbeat*. It's additionally used as a source for healthchecks and will impact the serving state of a tablet, if enabled. The heartbeat interval is purposefully kept distinct from the health check interval because lag measurement requires more frequent polling that the healthcheck typically is configured for.

Index

• Constants
• Variables
• func GhostBinaryFileName() (fileName string, isOverride bool)
• func PTOSCFileName() (fileName string, isOverride bool)
• func RandomHash() string
• func ReadableTimestamp() string
• func ToReadableTimestamp(t time.Time) string
• type Executor
  • func NewExecutor(env tabletenv.Env, ts *topo.Server, ...) *Executor
  • func (e *Executor) Close()
  • func (e *Executor) ExecuteWithGhost(ctx context.Context, onlineDDL *schema.OnlineDDL) error
  • func (e *Executor) ExecuteWithPTOSC(ctx context.Context, onlineDDL *schema.OnlineDDL) error
  • func (e *Executor) InitDBConfig(keyspace, shard, dbName string)
  • func (e *Executor) OnSchemaMigrationStatus(ctx context.Context, uuidParam, statusParam, dryrunParam string) (err error)
  • func (e *Executor) Open() error
  • func (e *Executor) VExec(ctx context.Context, vx *vexec.TabletVExec) (qr *querypb.QueryResult, err error)

Constants

const (
	// SchemaMigrationsTableName is used by VExec interceptor to call the correct handler
	SchemaMigrationsTableName = "schema_migrations"
)

Variables

var (
	// ErrExecutorNotWritableTablet  is generated when executor is asked to run gh-ost on a read-only server
	ErrExecutorNotWritableTablet = errors.New("Cannot run gh-ost migration on non-writable tablet")
	// ErrExecutorMigrationAlreadyRunning is generated when an attempt is made to run an operation that conflicts with a running migration
	ErrExecutorMigrationAlreadyRunning = errors.New("Cannot run gh-ost migration since a migration is already running")
	// ErrMigrationNotFound is returned by readMigration when given UUI cannot be found
	ErrMigrationNotFound = errors.New("Migration not found")
)

Functions

func GhostBinaryFileName

func GhostBinaryFileName() (fileName string, isOverride bool)

GhostBinaryFileName returns the full path+name of the gh-ost binary

func PTOSCFileName

func PTOSCFileName() (fileName string, isOverride bool)

PTOSCFileName returns the full path+name of the pt-online-schema-change binary Note that vttablet does not include pt-online-schema-change

func RandomHash

func RandomHash() string

RandomHash returns a 64 hex character random string

func ReadableTimestamp

func ReadableTimestamp() string

ReadableTimestamp returns a timestamp, in seconds resolution, that is human readable (as opposed to unix timestamp which is just a number), and which corresponds to the time now. Example: for Aug 25 2020, 16:04:25 we return "20200825160425"

func ToReadableTimestamp

func ToReadableTimestamp(t time.Time) string

ToReadableTimestamp returns a timestamp, in seconds resolution, that is human readable (as opposed to unix timestamp which is just a number) Example: for Aug 25 2020, 16:04:25 we return "20200825160425"

Types

type Executor

type Executor struct {
	// contains filtered or unexported fields
}

Executor wraps and manages the execution of a gh-ost migration.

func NewExecutor

func NewExecutor(env tabletenv.Env, ts *topo.Server, tabletTypeFunc func() topodatapb.TabletType) *Executor

NewExecutor creates a new gh-ost executor.

func (*Executor) Close

func (e *Executor) Close()

Close frees resources

func (*Executor) ExecuteWithGhost

func (e *Executor) ExecuteWithGhost(ctx context.Context, onlineDDL *schema.OnlineDDL) error

ExecuteWithGhost validates and runs a gh-ost process. Validation included testing the backend MySQL server and the gh-ost binary itself Execution runs first a dry run, then an actual migration

func (*Executor) ExecuteWithPTOSC

func (e *Executor) ExecuteWithPTOSC(ctx context.Context, onlineDDL *schema.OnlineDDL) error

ExecuteWithPTOSC validates and runs a pt-online-schema-change process. Validation included testing the backend MySQL server and the pt-online-schema-change binary itself Execution runs first a dry run, then an actual migration

func (*Executor) InitDBConfig

func (e *Executor) InitDBConfig(keyspace, shard, dbName string)

InitDBConfig initializes keysapce

func (*Executor) OnSchemaMigrationStatus

func (e *Executor) OnSchemaMigrationStatus(ctx context.Context, uuidParam, statusParam, dryrunParam string) (err error)

OnSchemaMigrationStatus is called by TabletServer's API, which is invoked by a running gh-ost migration's hooks.

func (*Executor) Open

func (e *Executor) Open() error

Open opens database pool and initializes the schema

func (*Executor) VExec

func (e *Executor) VExec(ctx context.Context, vx *vexec.TabletVExec) (qr *querypb.QueryResult, err error)

VExec is called by a VExec invocation