discovery

package
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 Go to latest Published: Jun 7, 2016 License: BSD-3-Clause Imports: 19 Imported by: 0

Documentation

Overview

Package discovery provides a way to discover all tablets e.g. within a specific shard and monitor their current health.

Use the HealthCheck object to query for tablets and their health.

For an example how to use the HealthCheck object, see worker/topo_utils.go.

Tablets have to be manually added to the HealthCheck using AddTablet(). Alternatively, use a Watcher implementation which will constantly watch a source (e.g. the topology) and add and remove tablets as they are added or removed from the source. For a Watcher example have a look at NewShardReplicationWatcher().

Note that the getter functions GetTabletStatsFrom* will always return an unfiltered list of all known tablets. Use the helper functions in utils.go to filter them e.g. RemoveUnhealthyTablets() or GetCurrentMaster(). replicationlag.go contains a more advanced health filter which is used by vtgate.

Internally, the HealthCheck module is connected to each tablet and has a streaming RPC (StreamHealth) open to receive periodic health infos.

Index

Constants

View Source 
const (
	// DefaultTopoReadConcurrency can be used as default value for the topoReadConcurrency parameter of a TopologyWatcher.
	DefaultTopoReadConcurrency int = 5
)

Variables

View Source 
var (
	// ErrWaitForTabletsTimeout is returned if we cannot get the tablets in time
	ErrWaitForTabletsTimeout = errors.New("timeout waiting for tablets")
)
View Source 
var (
	// LowReplicationLag defines the duration that replication lag is low enough that the VTTablet is considered healthy.
	LowReplicationLag = flag.Duration("discovery_low_replication_lag", 30*time.Second, "the replication lag that is considered low enough to be healthy")
)

Functions

func TabletToMapKey 

func TabletToMapKey(tablet *topodatapb.Tablet) string

TabletToMapKey creates a key to the map from tablet's host and ports. It should only be used in discovery and related module.

func WaitForAllServingTablets 

func WaitForAllServingTablets(ctx context.Context, hc HealthCheck, ts topo.SrvTopoServer, cell string, types []topodatapb.TabletType) error

WaitForAllServingTablets waits for at least one serving tablet in the given cell for all keyspaces / shards before returning.

func WaitForTablets 

func WaitForTablets(ctx context.Context, hc HealthCheck, cell, keyspace, shard string, types []topodatapb.TabletType) error

WaitForTablets waits for at least one tablet in the given cell / keyspace / shard before returning.

Types

type HealthCheck 

type HealthCheck interface {
	// RegisterStats registers the connection counts stats.
	// It can only be called on one Healthcheck object per process.
	RegisterStats()
	// SetListener sets the listener for healthcheck updates. It should not block.
	// Note that the default implementation requires to set the listener before
	// any tablets are added to the healthcheck.
	SetListener(listener HealthCheckStatsListener)
	// AddTablet adds the tablet, and starts health check.
	AddTablet(cell, name string, tablet *topodatapb.Tablet)
	// RemoveTablet removes the tablet, and stops the health check.
	RemoveTablet(tablet *topodatapb.Tablet)
	// GetTabletStatsFromKeyspaceShard returns all TabletStats for the given keyspace/shard.
	GetTabletStatsFromKeyspaceShard(keyspace, shard string) []*TabletStats
	// GetTabletStatsFromTarget returns all TabletStats for the given target.
	// You can exclude unhealthy entries using the helper in utils.go.
	GetTabletStatsFromTarget(keyspace, shard string, tabletType topodatapb.TabletType) []*TabletStats
	// GetConnection returns the TabletConn of the given tablet.
	GetConnection(tablet *topodatapb.Tablet) tabletconn.TabletConn
	// CacheStatus returns a displayable version of the cache.
	CacheStatus() TabletsCacheStatusList
	// Close stops the healthcheck.
	Close() error
}

HealthCheck defines the interface of health checking module.

func NewHealthCheck 

func NewHealthCheck(connTimeout time.Duration, retryDelay time.Duration, healthCheckTimeout time.Duration) HealthCheck

NewHealthCheck creates a new HealthCheck object.

type HealthCheckImpl 

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

HealthCheckImpl performs health checking and notifies downstream components about any changes.

func (*HealthCheckImpl) AddTablet 

func (hc *HealthCheckImpl) AddTablet(cell, name string, tablet *topodatapb.Tablet)

AddTablet adds the tablet, and starts health check. It does not block on making connection. name is an optional tag for the tablet, e.g. an alternative address.

func (*HealthCheckImpl) CacheStatus 

func (hc *HealthCheckImpl) CacheStatus() TabletsCacheStatusList

CacheStatus returns a displayable version of the cache.

func (*HealthCheckImpl) Close 

func (hc *HealthCheckImpl) Close() error

Close stops the healthcheck. After Close() returned, it's guaranteed that the listener won't be called anymore.

func (*HealthCheckImpl) GetConnection 

func (hc *HealthCheckImpl) GetConnection(tablet *topodatapb.Tablet) tabletconn.TabletConn

GetConnection returns the TabletConn of the given tablet.

func (*HealthCheckImpl) GetTabletStatsFromKeyspaceShard 

func (hc *HealthCheckImpl) GetTabletStatsFromKeyspaceShard(keyspace, shard string) []*TabletStats

GetTabletStatsFromKeyspaceShard returns all TabletStats for the given keyspace/shard.

func (*HealthCheckImpl) GetTabletStatsFromTarget 

func (hc *HealthCheckImpl) GetTabletStatsFromTarget(keyspace, shard string, tabletType topodatapb.TabletType) []*TabletStats

GetTabletStatsFromTarget returns all TabletStats for the given target.

func (*HealthCheckImpl) RegisterStats 

func (hc *HealthCheckImpl) RegisterStats()

RegisterStats registers the connection counts stats

func (*HealthCheckImpl) RemoveTablet 

func (hc *HealthCheckImpl) RemoveTablet(tablet *topodatapb.Tablet)

RemoveTablet removes the tablet, and stops the health check. It does not block.

func (*HealthCheckImpl) SetListener 

func (hc *HealthCheckImpl) SetListener(listener HealthCheckStatsListener)

SetListener sets the listener for healthcheck updates. It should not block. It must be called after NewHealthCheck and before any tablets are added (either through AddTablet or through a Watcher).

type HealthCheckStatsListener 

type HealthCheckStatsListener interface {
	StatsUpdate(*TabletStats)
}

HealthCheckStatsListener is the listener to receive health check stats update.

type TabletStats 

type TabletStats struct {
	Tablet                              *topodatapb.Tablet
	Name                                string // name is an optional tag (e.g. alternative address)
	Target                              *querypb.Target
	Up                                  bool // whether the tablet is added
	Serving                             bool // whether the server is serving
	TabletExternallyReparentedTimestamp int64
	Stats                               *querypb.RealtimeStats
	LastError                           error
}

TabletStats is returned when getting the set of tablets.

func FilterByReplicationLag 

func FilterByReplicationLag(tabletStatsList []*TabletStats) []*TabletStats

FilterByReplicationLag filters the list of TabletStats by TabletStats.Stats.SecondsBehindMaster. The algorithm (TabletStats that is non-serving or has error is ignored): - Return the list if there is 0 or 1 tablet. - Return the list if all tablets have <=30s lag. - Filter by replication lag: for each tablet, if the mean value without it is more than 0.7 of the mean value across all tablets, it is valid. - Make sure we return at least two tablets (if there is one with <2h replication lag). - If one tablet is removed, run above steps again in case there are two tablets with high replication lag. (It should cover most cases.) For example, lags of (5s, 10s, 15s, 120s) return the first three; lags of (30m, 35m, 40m, 45m) return all.

func GetCurrentMaster 

func GetCurrentMaster(tabletStatsList []*TabletStats) []*TabletStats

GetCurrentMaster returns the MASTER tablet with the highest TabletExternallyReparentedTimestamp value.

func RemoveUnhealthyTablets 

func RemoveUnhealthyTablets(tabletStatsList []*TabletStats) []*TabletStats

RemoveUnhealthyTablets filters all unhealthy tablets out. NOTE: Non-serving tablets are considered healthy.

func (*TabletStats) String 

func (e *TabletStats) String() string

String is defined because we want to print a []*TabletStats array nicely.

type TabletStatsList 

type TabletStatsList []*TabletStats

TabletStatsList is used for sorting.

func (TabletStatsList) Len 

func (tsl TabletStatsList) Len() int

Len is part of sort.Interface.

func (TabletStatsList) Less 

func (tsl TabletStatsList) Less(i, j int) bool

Less is part of sort.Interface

func (TabletStatsList) Swap 

func (tsl TabletStatsList) Swap(i, j int)

Swap is part of sort.Interface

type TabletsCacheStatus 

type TabletsCacheStatus struct {
	Cell         string
	Target       *querypb.Target
	TabletsStats TabletStatsList
}

TabletsCacheStatus is the current tablets for a cell/target. TODO: change this to reflect the e2e information about the tablets.

func (*TabletsCacheStatus) StatusAsHTML 

func (tcs *TabletsCacheStatus) StatusAsHTML() template.HTML

StatusAsHTML returns an HTML version of the status.

type TabletsCacheStatusList 

type TabletsCacheStatusList []*TabletsCacheStatus

TabletsCacheStatusList is used for sorting.

func (TabletsCacheStatusList) Len 

func (tcsl TabletsCacheStatusList) Len() int

Len is part of sort.Interface.

func (TabletsCacheStatusList) Less 

func (tcsl TabletsCacheStatusList) Less(i, j int) bool

Less is part of sort.Interface

func (TabletsCacheStatusList) Swap 

func (tcsl TabletsCacheStatusList) Swap(i, j int)

Swap is part of sort.Interface

type TopologyWatcher 

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

TopologyWatcher polls tablet from a configurable set of tablets periodically.

func NewCellTabletsWatcher 

func NewCellTabletsWatcher(topoServer topo.Server, hc HealthCheck, cell string, refreshInterval time.Duration, topoReadConcurrency int) *TopologyWatcher

NewCellTabletsWatcher returns a TopologyWatcher that monitors all the tablets in a cell, and starts refreshing.

func NewShardReplicationWatcher 

func NewShardReplicationWatcher(topoServer topo.Server, hc HealthCheck, cell, keyspace, shard string, refreshInterval time.Duration, topoReadConcurrency int) *TopologyWatcher

NewShardReplicationWatcher returns a TopologyWatcher that monitors the tablets in a cell/keyspace/shard, and starts refreshing.

func NewTopologyWatcher 

func NewTopologyWatcher(topoServer topo.Server, hc HealthCheck, cell string, refreshInterval time.Duration, topoReadConcurrency int, getTablets func(tw *TopologyWatcher) ([]*topodatapb.TabletAlias, error)) *TopologyWatcher

NewTopologyWatcher returns a TopologyWatcher that monitors all the tablets in a cell, and starts refreshing.

func (*TopologyWatcher) Stop 

func (tw *TopologyWatcher) Stop()

Stop stops the watcher. It does not clean up the tablets added to HealthCheck.

Source Files

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