discovery

package
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 Go to latest Published: Jul 27, 2021 License: Apache-2.0 Imports: 34 Imported by: 14

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 vtgate/tabletgateway.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 NewCellTabletsWatcher().

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

Package discovery provides a way to discover all tablets e.g. within a specific shard and monitor their current health. Deprecated Use the LegacyHealthCheck object to query for tablets and their health.

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

Tablets have to be manually added to the LegacyHealthCheck 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 NewLegacyShardReplicationWatcher().

Each LegacyHealthCheck has a LegacyHealthCheckStatsListener that will receive notification of when tablets go up and down. LegacyTabletStatsCache is one implementation, that caches the known tablets and the healthy ones per keyspace/shard/tabletType.

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

Index

Constants

View Source 
const (
	DefaultHealthCheckRetryDelay = 5 * time.Second
	DefaultHealthCheckTimeout    = 1 * time.Minute

	// DefaultTopoReadConcurrency is used as the default value for the TopoReadConcurrency parameter of a TopologyWatcher.
	DefaultTopoReadConcurrency int = 5
	// DefaultTopologyWatcherRefreshInterval is used as the default value for
	// the refresh interval of a topology watcher.
	DefaultTopologyWatcherRefreshInterval = 1 * time.Minute
	// HealthCheckTemplate is the HTML code to display a TabletsCacheStatusList
	HealthCheckTemplate = `` /* 652-byte string literal not displayed */

)

See the documentation for NewHealthCheck below for an explanation of these parameters.

View Source 
const (
	// LegacyHealthCheckTemplate is the HTML code to display a TabletsCacheStatusList
	LegacyHealthCheckTemplate = `` /* 651-byte string literal not displayed */

)

Variables

View Source 
var (

	// TabletURLTemplateString is a flag to generate URLs for the tablets that vtgate discovers.
	TabletURLTemplateString = flag.String("tablet_url_template", "http://{{.GetTabletHostPort}}", "format string describing debug tablet url formatting. See the Go code for getTabletDebugURL() how to customize this.")

	// AllowedTabletTypes is the list of allowed tablet types. e.g. {MASTER, REPLICA}
	AllowedTabletTypes []topodata.TabletType
	// TabletFilters are the keyspace|shard or keyrange filters to apply to the full set of tablets
	TabletFilters flagutil.StringListValue
	// KeyspacesToWatch - if provided this specifies which keyspaces should be
	// visible to the healthcheck. By default the healthcheck will watch all keyspaces.
	KeyspacesToWatch flagutil.StringListValue
	// RefreshInterval is the interval at which healthcheck refreshes its list of tablets from topo
	RefreshInterval = flag.Duration("tablet_refresh_interval", 1*time.Minute, "tablet refresh interval")
	// RefreshKnownTablets tells us whether to process all tablets or only new tablets
	RefreshKnownTablets = flag.Bool("tablet_refresh_known_tablets", true, "tablet refresh reloads the tablet address/port map from topo in case it changes")
	// TopoReadConcurrency tells us how many topo reads are allowed in parallel
	TopoReadConcurrency = flag.Int("topo_read_concurrency", 32, "concurrent topo reads")
)

Functions

func FilterTargetsByKeyspaces added in v0.8.0 

func FilterTargetsByKeyspaces(keyspaces []string, targets []*query.Target) []*query.Target

FilterTargetsByKeyspaces only returns the targets that are part of the provided keyspaces

func FilteringKeyspaces added in v0.10.0 

func FilteringKeyspaces() bool

FilteringKeyspaces returns true if any keyspaces have been configured to be filtered.

func GetHighReplicationLagMinServing added in v0.11.0 

func GetHighReplicationLagMinServing() time.Duration

GetHighReplicationLagMinServing getter for use by debugenv

func GetLowReplicationLag added in v0.11.0 

func GetLowReplicationLag() time.Duration

GetLowReplicationLag getter for use by debugenv

func GetMinNumTablets added in v0.11.0 

func GetMinNumTablets() int

GetMinNumTablets getter for use by debugenv

func GetTabletPickerRetryDelay added in v0.8.0 

func GetTabletPickerRetryDelay() time.Duration

GetTabletPickerRetryDelay synchronizes changes to tabletPickerRetryDelay. Used in tests only at the moment

func IsReplicationLagHigh 

func IsReplicationLagHigh(tabletHealth *TabletHealth) bool

IsReplicationLagHigh verifies that the given LegacytabletHealth refers to a tablet with high replication lag, i.e. higher than the configured discovery_low_replication_lag flag.

func IsReplicationLagVeryHigh 

func IsReplicationLagVeryHigh(tabletHealth *TabletHealth) bool

IsReplicationLagVeryHigh verifies that the given LegacytabletHealth refers to a tablet with very high replication lag, i.e. higher than the configured discovery_high_replication_lag_minimum_serving flag.

func LegacyIsReplicationLagHigh 

func LegacyIsReplicationLagHigh(tabletStats *LegacyTabletStats) bool

LegacyIsReplicationLagHigh verifies that the given LegacyTabletStats refers to a tablet with high replication lag, i.e. higher than the configured discovery_low_replication_lag flag.

func LegacyIsReplicationLagVeryHigh 

func LegacyIsReplicationLagVeryHigh(tabletStats *LegacyTabletStats) bool

LegacyIsReplicationLagVeryHigh verifies that the given LegacyTabletStats refers to a tablet with very high replication lag, i.e. higher than the configured discovery_high_replication_lag_minimum_serving flag.

func ParseTabletURLTemplateFromFlag 

func ParseTabletURLTemplateFromFlag()

ParseTabletURLTemplateFromFlag loads or reloads the URL template.

func SetHighReplicationLagMinServing added in v0.11.0 

func SetHighReplicationLagMinServing(lag time.Duration)

SetHighReplicationLagMinServing setter for use by debugenv

func SetLowReplicationLag added in v0.11.0 

func SetLowReplicationLag(lag time.Duration)

SetLowReplicationLag setter for use by debugenv

func SetMinNumTablets added in v0.11.0 

func SetMinNumTablets(numTablets int)

SetMinNumTablets setter for use by debugenv

func SetTabletPickerRetryDelay added in v0.8.0 

func SetTabletPickerRetryDelay(delay time.Duration)

SetTabletPickerRetryDelay synchronizes reads for tabletPickerRetryDelay. Used in tests only at the moment

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.

Types

type FakeHealthCheck 

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

FakeHealthCheck implements discovery.HealthCheck.

func NewFakeHealthCheck 

func NewFakeHealthCheck() *FakeHealthCheck

NewFakeHealthCheck returns the fake healthcheck object.

func (*FakeHealthCheck) AddFakeTablet 

func (fhc *FakeHealthCheck) AddFakeTablet(cell, host string, port int32, keyspace, shard string, tabletType topodatapb.TabletType, serving bool, reparentTS int64, err error, connFactory func(*topodatapb.Tablet) queryservice.QueryService) queryservice.QueryService

AddFakeTablet inserts a fake entry into FakeHealthCheck. The Tablet can be talked to using the provided connection. The Listener is called, as if AddTablet had been called. For flexibility the connection is created via a connFactory callback

func (*FakeHealthCheck) AddTablet 

func (fhc *FakeHealthCheck) AddTablet(tablet *topodatapb.Tablet)

AddTablet adds the tablet.

func (*FakeHealthCheck) AddTestTablet 

func (fhc *FakeHealthCheck) AddTestTablet(cell, host string, port int32, keyspace, shard string, tabletType topodatapb.TabletType, serving bool, reparentTS int64, err error) *sandboxconn.SandboxConn

AddTestTablet adds a fake tablet for tests using the SandboxConn and returns the fake connection

func (*FakeHealthCheck) CacheStatus 

func (fhc *FakeHealthCheck) CacheStatus() TabletsCacheStatusList

CacheStatus returns the status for each tablet

func (*FakeHealthCheck) Close 

func (fhc *FakeHealthCheck) Close() error

Close is not implemented.

func (*FakeHealthCheck) GetAllTablets 

func (fhc *FakeHealthCheck) GetAllTablets() map[string]*topodatapb.Tablet

GetAllTablets returns all the tablets we have.

func (*FakeHealthCheck) GetHealthyTabletStats 

func (fhc *FakeHealthCheck) GetHealthyTabletStats(target *querypb.Target) []*TabletHealth

GetHealthyTabletStats returns only the healthy tablets - Serving true and LastError is not nil

func (*FakeHealthCheck) RegisterStats 

func (fhc *FakeHealthCheck) RegisterStats()

RegisterStats is not implemented.

func (*FakeHealthCheck) RemoveTablet 

func (fhc *FakeHealthCheck) RemoveTablet(tablet *topodatapb.Tablet)

RemoveTablet removes the tablet.

func (*FakeHealthCheck) ReplaceTablet 

func (fhc *FakeHealthCheck) ReplaceTablet(old, new *topodatapb.Tablet)

ReplaceTablet removes the old tablet and adds the new.

func (*FakeHealthCheck) Reset 

func (fhc *FakeHealthCheck) Reset()

Reset cleans up the internal state.

func (*FakeHealthCheck) Subscribe 

func (fhc *FakeHealthCheck) Subscribe() chan *TabletHealth

Subscribe is not implemented.

func (*FakeHealthCheck) TabletConnection 

func (fhc *FakeHealthCheck) TabletConnection(alias *topodatapb.TabletAlias, target *querypb.Target) (queryservice.QueryService, error)

TabletConnection returns the TabletConn of the given tablet.

func (*FakeHealthCheck) Unsubscribe 

func (fhc *FakeHealthCheck) Unsubscribe(c chan *TabletHealth)

Unsubscribe is not implemented.

func (*FakeHealthCheck) WaitForAllServingTablets 

func (fhc *FakeHealthCheck) WaitForAllServingTablets(ctx context.Context, targets []*querypb.Target) error

WaitForAllServingTablets is not implemented.

type FakeLegacyHealthCheck 

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

FakeLegacyHealthCheck implements discovery.LegacyHealthCheck.

func NewFakeLegacyHealthCheck 

func NewFakeLegacyHealthCheck() *FakeLegacyHealthCheck

NewFakeLegacyHealthCheck returns the fake healthcheck object.

func (*FakeLegacyHealthCheck) AddFakeTablet 

func (fhc *FakeLegacyHealthCheck) AddFakeTablet(cell, host string, port int32, keyspace, shard string, tabletType topodatapb.TabletType, serving bool, reparentTS int64, err error, connFactory func(*topodatapb.Tablet) queryservice.QueryService) queryservice.QueryService

AddFakeTablet inserts a fake entry into FakeLegacyHealthCheck. The Tablet can be talked to using the provided connection. The Listener is called, as if AddTablet had been called. For flexibility the connection is created via a connFactory callback

func (*FakeLegacyHealthCheck) AddTablet 

func (fhc *FakeLegacyHealthCheck) AddTablet(tablet *topodatapb.Tablet, name string)

AddTablet adds the tablet and calls the listener.

func (*FakeLegacyHealthCheck) AddTestTablet 

func (fhc *FakeLegacyHealthCheck) AddTestTablet(cell, host string, port int32, keyspace, shard string, tabletType topodatapb.TabletType, serving bool, reparentTS int64, err error) *sandboxconn.SandboxConn

AddTestTablet adds a fake tablet for tests using the SandboxConn and returns the fake connection

func (*FakeLegacyHealthCheck) CacheStatus 

func (fhc *FakeLegacyHealthCheck) CacheStatus() LegacyTabletsCacheStatusList

CacheStatus returns the status for each tablet

func (*FakeLegacyHealthCheck) Close 

func (fhc *FakeLegacyHealthCheck) Close() error

Close is not implemented.

func (*FakeLegacyHealthCheck) GetAllTablets 

func (fhc *FakeLegacyHealthCheck) GetAllTablets() map[string]*topodatapb.Tablet

GetAllTablets returns all the tablets we have.

func (*FakeLegacyHealthCheck) GetConnection 

func (fhc *FakeLegacyHealthCheck) GetConnection(key string) queryservice.QueryService

GetConnection returns the TabletConn of the given tablet.

func (*FakeLegacyHealthCheck) RegisterStats 

func (fhc *FakeLegacyHealthCheck) RegisterStats()

RegisterStats is not implemented.

func (*FakeLegacyHealthCheck) RemoveTablet 

func (fhc *FakeLegacyHealthCheck) RemoveTablet(tablet *topodatapb.Tablet)

RemoveTablet removes the tablet.

func (*FakeLegacyHealthCheck) ReplaceTablet 

func (fhc *FakeLegacyHealthCheck) ReplaceTablet(old, new *topodatapb.Tablet, name string)

ReplaceTablet removes the old tablet and adds the new.

func (*FakeLegacyHealthCheck) Reset 

func (fhc *FakeLegacyHealthCheck) Reset()

Reset cleans up the internal state.

func (*FakeLegacyHealthCheck) SetListener 

func (fhc *FakeLegacyHealthCheck) SetListener(listener LegacyHealthCheckStatsListener, sendDownEvents bool)

SetListener is not implemented.

func (*FakeLegacyHealthCheck) WaitForInitialStatsUpdates 

func (fhc *FakeLegacyHealthCheck) WaitForInitialStatsUpdates()

WaitForInitialStatsUpdates is not implemented.

type FilterByKeyspace 

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

FilterByKeyspace is a filter that filters tablets by keyspace

func NewFilterByKeyspace 

func NewFilterByKeyspace(selectedKeyspaces []string) *FilterByKeyspace

NewFilterByKeyspace creates a new FilterByKeyspace. Each filter is a keyspace entry. All tablets that match a keyspace will be forwarded to the underlying LegacyTabletRecorder.

func (*FilterByKeyspace) IsIncluded 

func (fbk *FilterByKeyspace) IsIncluded(tablet *topodata.Tablet) bool

IsIncluded returns true if the tablet's keyspace should be forwarded to the underlying LegacyTabletRecorder.

type FilterByShard 

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

FilterByShard is a filter that filters tablets by keyspace/shard.

func NewFilterByShard 

func NewFilterByShard(filters []string) (*FilterByShard, error)

NewFilterByShard creates a new FilterByShard on top of an existing LegacyTabletRecorder. Each filter is a keyspace|shard entry, where shard can either be a shard name, or a keyrange. All tablets that match at least one keyspace|shard tuple will be forwarded to the underlying LegacyTabletRecorder.

func (*FilterByShard) IsIncluded 

func (fbs *FilterByShard) IsIncluded(tablet *topodata.Tablet) bool

IsIncluded returns true iff the tablet's keyspace and shard should be forwarded to the underlying LegacyTabletRecorder.

type HealthCheck 

type HealthCheck interface {
	// CacheStatus returns a displayable version of the health check cache.
	CacheStatus() TabletsCacheStatusList

	// Close stops the healthcheck.
	Close() error

	// WaitForAllServingTablets waits for at least one healthy serving tablet in
	// each given target before returning.
	// It will return ctx.Err() if the context is canceled.
	// It will return an error if it can't read the necessary topology records.
	WaitForAllServingTablets(ctx context.Context, targets []*query.Target) error

	// TabletConnection returns the TabletConn of the given tablet.
	TabletConnection(alias *topodata.TabletAlias, target *query.Target) (queryservice.QueryService, error)

	// RegisterStats registers the connection counts stats
	RegisterStats()

	// GetHealthyTabletStats returns only the healthy tablets.
	// The returned array is owned by the caller.
	// For TabletType_MASTER, this will only return at most one entry,
	// the most recent tablet of type master.
	// This returns a copy of the data so that callers can access without
	// synchronization
	GetHealthyTabletStats(target *query.Target) []*TabletHealth

	// Subscribe adds a listener. Used by vtgate buffer to learn about master changes.
	Subscribe() chan *TabletHealth

	// Unsubscribe removes a listener.
	Unsubscribe(c chan *TabletHealth)
}

HealthCheck declares what the TabletGateway needs from the HealthCheck

type HealthCheckImpl 

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

HealthCheckImpl performs health checking and stores the results. The goal of this object is to maintain a StreamHealth RPC to a lot of tablets. Tablets are added / removed by calling the AddTablet / RemoveTablet methods (other discovery module objects can for instance watch the topology and call these). It contains a map of tabletHealthCheck objects by Alias. Each tabletHealthCheck object stores the health information for one tablet. A checkConn goroutine is spawned for each tabletHealthCheck, which is responsible for keeping that tabletHealthCheck up-to-date. If checkConn terminates for any reason, then the corresponding tabletHealthCheck object is removed from the map. When a tabletHealthCheck gets removed from the map, its cancelFunc gets called, which ensures that the associated checkConn goroutine eventually terminates.

func NewHealthCheck 

func NewHealthCheck(ctx context.Context, retryDelay, healthCheckTimeout time.Duration, topoServer *topo.Server, localCell, cellsToWatch string) *HealthCheckImpl

NewHealthCheck creates a new HealthCheck object. Parameters: retryDelay. 

The duration to wait before retrying to connect (e.g. after a failed connection
attempt).

healthCheckTimeout. 

The duration for which we consider a health check response to be 'fresh'. If we don't get
a health check response from a tablet for more than this duration, we consider the tablet
not healthy.

topoServer. 

The topology server that this healthcheck object can use to retrieve cell or tablet information

localCell. 

The localCell for this healthcheck

callback. 

A function to call when there is a master change. Used to notify vtgate's buffer to stop buffering.

func (*HealthCheckImpl) AddTablet 

func (hc *HealthCheckImpl) AddTablet(tablet *topodata.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.

func (*HealthCheckImpl) GetHealthyTabletStats 

func (hc *HealthCheckImpl) GetHealthyTabletStats(target *query.Target) []*TabletHealth

GetHealthyTabletStats returns only the healthy tablets. The returned array is owned by the caller. For TabletType_MASTER, this will only return at most one entry, the most recent tablet of type master. This returns a copy of the data so that callers can access without synchronization

func (*HealthCheckImpl) RegisterStats 

func (hc *HealthCheckImpl) RegisterStats()

RegisterStats registers the connection counts stats

func (*HealthCheckImpl) RemoveTablet 

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

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

func (*HealthCheckImpl) ReplaceTablet 

func (hc *HealthCheckImpl) ReplaceTablet(old, new *topodata.Tablet)

ReplaceTablet removes the old tablet and adds the new tablet.

func (*HealthCheckImpl) ServeHTTP 

func (hc *HealthCheckImpl) ServeHTTP(w http.ResponseWriter, _ *http.Request)

ServeHTTP is part of the http.Handler interface. It renders the current state of the discovery gateway tablet cache into json.

func (*HealthCheckImpl) Subscribe 

func (hc *HealthCheckImpl) Subscribe() chan *TabletHealth

Subscribe adds a listener. Used by vtgate buffer to learn about master changes.

func (*HealthCheckImpl) TabletConnection 

func (hc *HealthCheckImpl) TabletConnection(alias *topodata.TabletAlias, target *query.Target) (queryservice.QueryService, error)

TabletConnection returns the Connection to a given tablet.

func (*HealthCheckImpl) Unsubscribe 

func (hc *HealthCheckImpl) Unsubscribe(c chan *TabletHealth)

Unsubscribe removes a listener.

func (*HealthCheckImpl) WaitForAllServingTablets 

func (hc *HealthCheckImpl) WaitForAllServingTablets(ctx context.Context, targets []*query.Target) error

WaitForAllServingTablets waits for at least one healthy serving tablet in each given target before returning. It will return ctx.Err() if the context is canceled. It will return an error if it can't read the necessary topology records.

func (*HealthCheckImpl) WaitForTablets 

func (hc *HealthCheckImpl) WaitForTablets(ctx context.Context, keyspace, shard string, tabletType topodata.TabletType) error

WaitForTablets waits for at least one tablet in the given keyspace / shard / tablet type before returning. The tablets do not have to be healthy. It will return ctx.Err() if the context is canceled.

type LegacyFilterByKeyspace 

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

LegacyFilterByKeyspace is a LegacyTabletRecorder filter that filters tablets by keyspace

func NewLegacyFilterByKeyspace 

func NewLegacyFilterByKeyspace(tr LegacyTabletRecorder, selectedKeyspaces []string) *LegacyFilterByKeyspace

NewLegacyFilterByKeyspace creates a new LegacyFilterByKeyspace on top of an existing LegacyTabletRecorder. Each filter is a keyspace entry. All tablets that match a keyspace will be forwarded to the underlying LegacyTabletRecorder.

func (*LegacyFilterByKeyspace) AddTablet 

func (fbk *LegacyFilterByKeyspace) AddTablet(tablet *topodatapb.Tablet, name string)

AddTablet is part of the LegacyTabletRecorder interface.

func (*LegacyFilterByKeyspace) RemoveTablet 

func (fbk *LegacyFilterByKeyspace) RemoveTablet(tablet *topodatapb.Tablet)

RemoveTablet is part of the LegacyTabletRecorder interface.

func (*LegacyFilterByKeyspace) ReplaceTablet 

func (fbk *LegacyFilterByKeyspace) ReplaceTablet(old *topodatapb.Tablet, new *topodatapb.Tablet, name string)

ReplaceTablet is part of the LegacyTabletRecorder interface.

type LegacyFilterByShard 

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

LegacyFilterByShard is a LegacyTabletRecorder filter that filters tablets by keyspace/shard.

func NewLegacyFilterByShard 

func NewLegacyFilterByShard(tr LegacyTabletRecorder, filters []string) (*LegacyFilterByShard, error)

NewLegacyFilterByShard creates a new LegacyFilterByShard on top of an existing LegacyTabletRecorder. Each filter is a keyspace|shard entry, where shard can either be a shard name, or a keyrange. All tablets that match at least one keyspace|shard tuple will be forwarded to the underlying LegacyTabletRecorder.

func (*LegacyFilterByShard) AddTablet 

func (fbs *LegacyFilterByShard) AddTablet(tablet *topodatapb.Tablet, name string)

AddTablet is part of the LegacyTabletRecorder interface.

func (*LegacyFilterByShard) RemoveTablet 

func (fbs *LegacyFilterByShard) RemoveTablet(tablet *topodatapb.Tablet)

RemoveTablet is part of the LegacyTabletRecorder interface.

func (*LegacyFilterByShard) ReplaceTablet 

func (fbs *LegacyFilterByShard) ReplaceTablet(old, new *topodatapb.Tablet, name string)

ReplaceTablet is part of the LegacyTabletRecorder interface.

type LegacyHealthCheck 

type LegacyHealthCheck interface {
	// LegacyTabletRecorder interface adds AddTablet and RemoveTablet methods.
	// AddTablet adds the tablet, and starts health check on it.
	// RemoveTablet removes the tablet, and stops its StreamHealth RPC.
	LegacyTabletRecorder

	// RegisterStats registers the connection counts and checksum stats.
	// It can only be called on one Healthcheck object per process.
	RegisterStats()
	// SetListener sets the listener for healthcheck
	// updates. sendDownEvents is used when a tablet changes type
	// (from replica to master for instance). If the listener
	// wants two events (Up=false on old type, Up=True on new
	// type), sendDownEvents should be set. Otherwise, the
	// healthcheck will only send one event (Up=true on new type).
	//
	// Note that the default implementation requires to set the
	// listener before any tablets are added to the healthcheck.
	SetListener(listener LegacyHealthCheckStatsListener, sendDownEvents bool)
	// WaitForInitialStatsUpdates waits until all tablets added via
	// AddTablet() call were propagated to the listener via correspondingdiscovert
	// StatsUpdate() calls. Note that code path from AddTablet() to
	// corresponding StatsUpdate() is asynchronous but not cancelable, thus
	// this function is also non-cancelable and can't return error. Also
	// note that all AddTablet() calls should happen before calling this
	// method. WaitForInitialStatsUpdates won't wait for StatsUpdate() calls
	// corresponding to AddTablet() calls made during its execution.
	WaitForInitialStatsUpdates()
	// GetConnection returns the TabletConn of the given tablet.
	GetConnection(key string) queryservice.QueryService
	// CacheStatus returns a displayable version of the cache.
	CacheStatus() LegacyTabletsCacheStatusList
	// Close stops the healthcheck.
	Close() error
}

LegacyHealthCheck defines the interface of health checking module. The goal of this object is to maintain a StreamHealth RPC to a lot of tablets. Tablets are added / removed by calling the AddTablet / RemoveTablet methods (other discovery module objects can for instance watch the topology and call these).

Updates to the health of all registered tablet can be watched by registering a listener. To get the underlying "TabletConn" object which is used for each tablet, use the "GetConnection()" method below and pass in the Key string which is also sent to the listener in each update (as it is part of LegacyTabletStats).

func NewLegacyDefaultHealthCheck 

func NewLegacyDefaultHealthCheck() LegacyHealthCheck

NewLegacyDefaultHealthCheck creates a new LegacyHealthCheck object with a default configuration.

func NewLegacyHealthCheck 

func NewLegacyHealthCheck(retryDelay, healthCheckTimeout time.Duration) LegacyHealthCheck

NewLegacyHealthCheck creates a new LegacyHealthCheck object. Parameters: retryDelay. 

The duration to wait before retrying to connect (e.g. after a failed connection
attempt).

healthCheckTimeout. 

The duration for which we consider a health check response to be 'fresh'. If we don't get
a health check response from a tablet for more than this duration, we consider the tablet
not healthy.

type LegacyHealthCheckImpl 

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

LegacyHealthCheckImpl performs health checking and notifies downstream components about any changes. It contains a map of legacyTabletHealth objects, each of which stores the health information for a tablet. A checkConn goroutine is spawned for each legacyTabletHealth, which is responsible for keeping that legacyTabletHealth up-to-date. This is done through callbacks to updateHealth. If checkConn terminates for any reason, it updates legacyTabletHealth.Up as false. If a legacyTabletHealth gets removed from the map, its cancelFunc gets called, which ensures that the associated checkConn goroutine eventually terminates.

func (*LegacyHealthCheckImpl) AddTablet 

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

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 (*LegacyHealthCheckImpl) CacheStatus 

func (hc *LegacyHealthCheckImpl) CacheStatus() LegacyTabletsCacheStatusList

CacheStatus returns a displayable version of the cache.

func (*LegacyHealthCheckImpl) Close 

func (hc *LegacyHealthCheckImpl) Close() error

Close stops the healthcheck. After Close() returned, it's guaranteed that the listener isn't currently executing and won't be called again.

func (*LegacyHealthCheckImpl) GetConnection 

func (hc *LegacyHealthCheckImpl) GetConnection(key string) queryservice.QueryService

GetConnection returns the TabletConn of the given tablet.

func (*LegacyHealthCheckImpl) RegisterStats 

func (hc *LegacyHealthCheckImpl) RegisterStats()

RegisterStats registers the connection counts stats

func (*LegacyHealthCheckImpl) RemoveTablet 

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

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

func (*LegacyHealthCheckImpl) ReplaceTablet 

func (hc *LegacyHealthCheckImpl) ReplaceTablet(old, new *topodatapb.Tablet, name string)

ReplaceTablet removes the old tablet and adds the new tablet.

func (*LegacyHealthCheckImpl) ServeHTTP 

func (hc *LegacyHealthCheckImpl) ServeHTTP(w http.ResponseWriter, _ *http.Request)

ServeHTTP is part of the http.Handler interface. It renders the current state of the discovery gateway tablet cache into json.

func (*LegacyHealthCheckImpl) SetListener 

func (hc *LegacyHealthCheckImpl) SetListener(listener LegacyHealthCheckStatsListener, sendDownEvents bool)

SetListener sets the listener for healthcheck updates. It must be called after NewLegacyHealthCheck and before any tablets are added (either through AddTablet or through a Watcher).

func (*LegacyHealthCheckImpl) WaitForInitialStatsUpdates 

func (hc *LegacyHealthCheckImpl) WaitForInitialStatsUpdates()

WaitForInitialStatsUpdates waits until all tablets added via AddTablet() call were propagated to downstream via corresponding StatsUpdate() calls.

type LegacyHealthCheckStatsListener 

type LegacyHealthCheckStatsListener interface {
	// StatsUpdate is called when:
	// - a new tablet is known to the LegacyHealthCheck, and its first
	//   streaming healthcheck is returned. (then ts.Up is true).
	// - a tablet is removed from the list of tablets we watch
	//   (then ts.Up is false).
	// - a tablet dynamically changes its type. When registering the
	//   listener, if sendDownEvents is true, two events are generated
	//   (ts.Up false on the old type, ts.Up true on the new type).
	//   If it is false, only one event is sent (ts.Up true on the new
	//   type).
	StatsUpdate(*LegacyTabletStats)
}

LegacyHealthCheckStatsListener is the listener to receive health check stats update.

type LegacyTabletRecorder 

type LegacyTabletRecorder interface {
	// AddTablet adds the tablet.
	// Name is an alternate name, like an address.
	AddTablet(tablet *topodatapb.Tablet, name string)

	// RemoveTablet removes the tablet.
	RemoveTablet(tablet *topodatapb.Tablet)

	// ReplaceTablet does an AddTablet and RemoveTablet in one call, effectively replacing the old tablet with the new.
	ReplaceTablet(old, new *topodatapb.Tablet, name string)
}

LegacyTabletRecorder is the part of the LegacyHealthCheck interface that can add or remove tablets. We define it as a sub-interface here so we can add filters on tablets if needed.

type LegacyTabletStats 

type LegacyTabletStats struct {
	// Key uniquely identifies that serving tablet. It is computed
	// from the Tablet's record Hostname and PortMap. If a tablet
	// is restarted on different ports, its Key will be different.
	// Key is computed using the TabletToMapKey method below.
	// key can be used in GetConnection().
	Key string
	// Tablet is the tablet object that was sent to LegacyHealthCheck.AddTablet.
	Tablet *topodatapb.Tablet
	// Name is an optional tag (e.g. alternative address) for the
	// tablet.  It is supposed to represent the tablet as a task,
	// not as a process.  For instance, it can be a
	// cell+keyspace+shard+tabletType+taskIndex value.
	Name string
	// Target is the current target as returned by the streaming
	// StreamHealth RPC.
	Target *querypb.Target
	// Up describes whether the tablet is added or removed.
	Up bool
	// Serving describes if the tablet can be serving traffic.
	Serving bool
	// TabletExternallyReparentedTimestamp is the last timestamp
	// that this tablet was either elected the master, or received
	// a TabletExternallyReparented event. It is set to 0 if the
	// tablet doesn't think it's a master.
	TabletExternallyReparentedTimestamp int64
	// Stats is the current health status, as received by the
	// StreamHealth RPC (replication lag, ...).
	Stats *querypb.RealtimeStats
	// LastError is the error we last saw when trying to get the
	// tablet's healthcheck.
	LastError error
}

LegacyTabletStats is returned when getting the set of tablets.

func FilterLegacyStatsByReplicationLag 

func FilterLegacyStatsByReplicationLag(tabletStatsList []*LegacyTabletStats) []*LegacyTabletStats

FilterLegacyStatsByReplicationLag filters the list of LegacyTabletStats by LegacyTabletStats.Stats.SecondsBehindMaster. Note that LegacyTabletStats that is non-serving or has error is ignored.

The simplified logic: - Return tablets that have lag <= lowReplicationLag. - Make sure we return at least minNumTablets tablets, if there are enough one with lag <= highReplicationLagMinServing. For example, with the default of 30s / 2h / 2, this means: - lags of (5s, 10s, 15s, 120s) return the first three - lags of (30m, 35m, 40m, 45m) return the first two - lags of (2h, 3h, 4h, 5h) return the first one

The legacy algorithm (default for now): - 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 minNumTablets tablets (if there are enough one with only low 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.

One thing to know about this code: vttablet also has a couple flags that impact the logic here:

  • unhealthy_threshold: if replication lag is higher than this, a tablet will be reported as unhealthy. The default for this is 2h, same as the discovery_high_replication_lag_minimum_serving here.
  • degraded_threshold: this is only used by vttablet for display. It should match discovery_low_replication_lag here, so the vttablet status display matches what vtgate will do of it.

func RemoveUnhealthyTablets 

func RemoveUnhealthyTablets(tabletStatsList []LegacyTabletStats) []LegacyTabletStats

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

func (*LegacyTabletStats) Copy 

func (e *LegacyTabletStats) Copy() *LegacyTabletStats

Copy produces a copy of LegacyTabletStats.

func (*LegacyTabletStats) DeepEqual 

func (e *LegacyTabletStats) DeepEqual(f *LegacyTabletStats) bool

DeepEqual compares two LegacyTabletStats. Since we include protos, we need to use proto.Equal on these.

func (LegacyTabletStats) GetHostNameLevel 

func (e LegacyTabletStats) GetHostNameLevel(level int) string

GetHostNameLevel returns the specified hostname level. If the level does not exist it will pick the closest level. This seems unused but can be utilized by certain url formatting templates. See getTabletDebugURL for more details.

func (LegacyTabletStats) GetTabletHostPort 

func (e LegacyTabletStats) GetTabletHostPort() string

GetTabletHostPort formats a tablet host port address.

func (LegacyTabletStats) NamedStatusURL 

func (e LegacyTabletStats) NamedStatusURL() string

NamedStatusURL returns the URL for the case where a tablet server is named.

func (*LegacyTabletStats) String 

func (e *LegacyTabletStats) String() string

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

func (*LegacyTabletStats) TrivialStatsUpdate 

func (e *LegacyTabletStats) TrivialStatsUpdate(n *LegacyTabletStats) bool

TrivialStatsUpdate returns true iff the old and new LegacyTabletStats haven't changed enough to warrant re-calling FilterLegacyStatsByReplicationLag.

type LegacyTabletStatsCache 

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

LegacyTabletStatsCache is a LegacyHealthCheckStatsListener that keeps both the current list of available LegacyTabletStats, and a serving list: - for master tablets, only the current master is kept. - for non-master tablets, we filter the list using FilterLegacyStatsByReplicationLag. It keeps entries for all tablets in the cell(s) it's configured to serve for, and for the master independently of which cell it's in. Note the healthy tablet computation is done when we receive a tablet update only, not at serving time. Also note the cache may not have the last entry received by the tablet. For instance, if a tablet was healthy, and is still healthy, we do not keep its new update.

func NewLegacyTabletStatsCache 

func NewLegacyTabletStatsCache(hc LegacyHealthCheck, ts *topo.Server, cell string) *LegacyTabletStatsCache

NewLegacyTabletStatsCache creates a LegacyTabletStatsCache, and registers it as LegacyHealthCheckStatsListener of the provided healthcheck. Note we do the registration in this code to guarantee we call SetListener with sendDownEvents=true, as we need these events to maintain the integrity of our cache.

func NewTabletStatsCacheDoNotSetListener 

func NewTabletStatsCacheDoNotSetListener(ts *topo.Server, cell string) *LegacyTabletStatsCache

NewTabletStatsCacheDoNotSetListener is identical to NewLegacyTabletStatsCache but does not automatically set the returned object as listener for "hc". Instead, it's up to the caller to ensure that LegacyTabletStatsCache.StatsUpdate() gets called properly. This is useful for chaining multiple listeners. When the caller sets its own listener on "hc", they must make sure that they set the parameter "sendDownEvents" to "true" or this cache won't properly remove tablets whose tablet type changes.

func (*LegacyTabletStatsCache) GetHealthyTabletStats 

func (tc *LegacyTabletStatsCache) GetHealthyTabletStats(keyspace, shard string, tabletType topodatapb.TabletType) []LegacyTabletStats

GetHealthyTabletStats returns only the healthy targets. The returned array is owned by the caller. For TabletType_MASTER, this will only return at most one entry, the most recent tablet of type master.

func (*LegacyTabletStatsCache) GetTabletStats 

func (tc *LegacyTabletStatsCache) GetTabletStats(keyspace, shard string, tabletType topodatapb.TabletType) []LegacyTabletStats

GetTabletStats returns the full list of available targets. The returned array is owned by the caller.

func (*LegacyTabletStatsCache) ResetForTesting 

func (tc *LegacyTabletStatsCache) ResetForTesting()

ResetForTesting is for use in tests only.

func (*LegacyTabletStatsCache) StatsUpdate 

func (tc *LegacyTabletStatsCache) StatsUpdate(ts *LegacyTabletStats)

StatsUpdate is part of the LegacyHealthCheckStatsListener interface.

func (*LegacyTabletStatsCache) WaitByFilter 

func (tc *LegacyTabletStatsCache) WaitByFilter(ctx context.Context, keyspace, shard string, tabletTypes []topodatapb.TabletType, filter func([]LegacyTabletStats) []LegacyTabletStats) error

WaitByFilter waits for at least one tablet based on the filter function.

func (*LegacyTabletStatsCache) WaitForAllServingTablets 

func (tc *LegacyTabletStatsCache) WaitForAllServingTablets(ctx context.Context, targets []*querypb.Target) error

WaitForAllServingTablets waits for at least one healthy serving tablet in each given target before returning. It will return ctx.Err() if the context is canceled. It will return an error if it can't read the necessary topology records.

func (*LegacyTabletStatsCache) WaitForTablets 

func (tc *LegacyTabletStatsCache) WaitForTablets(ctx context.Context, keyspace, shard string, tabletType topodatapb.TabletType) error

WaitForTablets waits for at least one tablet in the given keyspace / shard / tablet type before returning. The tablets do not have to be healthy. It will return ctx.Err() if the context is canceled.

type LegacyTabletStatsList 

type LegacyTabletStatsList []*LegacyTabletStats

LegacyTabletStatsList is used for sorting.

func (LegacyTabletStatsList) Len 

func (tsl LegacyTabletStatsList) Len() int

Len is part of sort.Interface.

func (LegacyTabletStatsList) Less 

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

Less is part of sort.Interface

func (LegacyTabletStatsList) Swap 

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

Swap is part of sort.Interface

type LegacyTabletsCacheStatus 

type LegacyTabletsCacheStatus struct {
	Cell         string
	Target       *querypb.Target
	TabletsStats LegacyTabletStatsList
}

LegacyTabletsCacheStatus is the current tablets for a cell/target.

func (*LegacyTabletsCacheStatus) StatusAsHTML 

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

StatusAsHTML returns an HTML version of the status.

type LegacyTabletsCacheStatusList 

type LegacyTabletsCacheStatusList []*LegacyTabletsCacheStatus

LegacyTabletsCacheStatusList is used for sorting.

func (LegacyTabletsCacheStatusList) Len 

func (tcsl LegacyTabletsCacheStatusList) Len() int

Len is part of sort.Interface.

func (LegacyTabletsCacheStatusList) Less 

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

Less is part of sort.Interface

func (LegacyTabletsCacheStatusList) Swap 

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

Swap is part of sort.Interface

type LegacyTopologyWatcher 

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

LegacyTopologyWatcher polls tablet from a configurable set of tablets periodically. When tablets are added / removed, it calls the LegacyTabletRecorder AddTablet / RemoveTablet interface appropriately.

func NewLegacyCellTabletsWatcher 

func NewLegacyCellTabletsWatcher(ctx context.Context, topoServer *topo.Server, tr LegacyTabletRecorder, cell string, refreshInterval time.Duration, refreshKnownTablets bool, topoReadConcurrency int) *LegacyTopologyWatcher

NewLegacyCellTabletsWatcher returns a LegacyTopologyWatcher that monitors all the tablets in a cell, and starts refreshing.

func NewLegacyShardReplicationWatcher 

func NewLegacyShardReplicationWatcher(ctx context.Context, topoServer *topo.Server, tr LegacyTabletRecorder, cell, keyspace, shard string, refreshInterval time.Duration, topoReadConcurrency int) *LegacyTopologyWatcher

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

func NewLegacyTopologyWatcher 

func NewLegacyTopologyWatcher(ctx context.Context, topoServer *topo.Server, tr LegacyTabletRecorder, cell string, refreshInterval time.Duration, refreshKnownTablets bool, topoReadConcurrency int, getTablets func(tw *LegacyTopologyWatcher) ([]*topodatapb.TabletAlias, error)) *LegacyTopologyWatcher

NewLegacyTopologyWatcher returns a LegacyTopologyWatcher that monitors all the tablets in a cell, and starts refreshing.

func (*LegacyTopologyWatcher) RefreshLag 

func (tw *LegacyTopologyWatcher) RefreshLag() time.Duration

RefreshLag returns the time since the last refresh

func (*LegacyTopologyWatcher) Stop 

func (tw *LegacyTopologyWatcher) Stop()

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

func (*LegacyTopologyWatcher) TopoChecksum 

func (tw *LegacyTopologyWatcher) TopoChecksum() uint32

TopoChecksum returns the checksum of the current state of the topo

func (*LegacyTopologyWatcher) WaitForInitialTopology 

func (tw *LegacyTopologyWatcher) WaitForInitialTopology() error

WaitForInitialTopology waits until the watcher reads all of the topology data for the first time and transfers the information to LegacyTabletRecorder via its AddTablet() method.

type TabletFilter 

type TabletFilter interface {
	// IsIncluded returns whether tablet is included in this filter
	IsIncluded(tablet *topodata.Tablet) bool
}

TabletFilter is an interface that can be given to a TopologyWatcher to be applied as an additional filter on the list of tablets returned by its getTablets function

type TabletHealth 

type TabletHealth struct {
	Conn                queryservice.QueryService
	Tablet              *topodata.Tablet
	Target              *query.Target
	Stats               *query.RealtimeStats
	MasterTermStartTime int64
	LastError           error
	Serving             bool
}

TabletHealth represents simple tablet health data that is returned to users of healthcheck. No synchronization is required because we always return a copy.

func FilterStatsByReplicationLag 

func FilterStatsByReplicationLag(tabletHealthList []*TabletHealth) []*TabletHealth

FilterStatsByReplicationLag filters the list of TabletHealth by TabletHealth.Stats.SecondsBehindMaster. Note that TabletHealth that is non-serving or has error is ignored.

The simplified logic: - Return tablets that have lag <= lowReplicationLag. - Make sure we return at least minNumTablets tablets, if there are enough one with lag <= highReplicationLagMinServing. For example, with the default of 30s / 2h / 2, this means: - lags of (5s, 10s, 15s, 120s) return the first three - lags of (30m, 35m, 40m, 45m) return the first two - lags of (2h, 3h, 4h, 5h) return the first one

The legacy algorithm (default for now): - 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 minNumTablets tablets (if there are enough one with only low 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.

One thing to know about this code: vttablet also has a couple flags that impact the logic here:

  • unhealthy_threshold: if replication lag is higher than this, a tablet will be reported as unhealthy. The default for this is 2h, same as the discovery_high_replication_lag_minimum_serving here.
  • degraded_threshold: this is only used by vttablet for display. It should match discovery_low_replication_lag here, so the vttablet status display matches what vtgate will do of it.

func (*TabletHealth) DeepEqual 

func (th *TabletHealth) DeepEqual(other *TabletHealth) bool

DeepEqual compares two TabletHealth. Since we include protos, we need to use proto.Equal on these.

func (*TabletHealth) GetHostNameLevel 

func (th *TabletHealth) GetHostNameLevel(level int) string

GetHostNameLevel returns the specified hostname level. If the level does not exist it will pick the closest level. This seems unused but can be utilized by certain url formatting templates. See getTabletDebugURL for more details.

func (*TabletHealth) GetTabletHostPort 

func (th *TabletHealth) GetTabletHostPort() string

GetTabletHostPort formats a tablet host port address.

type TabletPicker 

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

TabletPicker gives a simplified API for picking tablets.

func NewTabletPicker 

func NewTabletPicker(ts *topo.Server, cells []string, keyspace, shard, tabletTypesStr string) (*TabletPicker, error)

NewTabletPicker returns a TabletPicker.

func (*TabletPicker) GetMatchingTablets added in v0.11.0 

func (tp *TabletPicker) GetMatchingTablets(ctx context.Context) []*topo.TabletInfo

GetMatchingTablets returns a list of TabletInfo for tablets that match the cells, keyspace, shard and tabletTypes for this TabletPicker

func (*TabletPicker) PickForStreaming 

func (tp *TabletPicker) PickForStreaming(ctx context.Context) (*topodatapb.Tablet, error)

PickForStreaming picks an available tablet All tablets that belong to tp.cells are evaluated and one is chosen at random

type TabletRecorder 

type TabletRecorder interface {
	// AddTablet adds the tablet.
	AddTablet(tablet *topodata.Tablet)
	// RemoveTablet removes the tablet.
	RemoveTablet(tablet *topodata.Tablet)
	// ReplaceTablet does an AddTablet and RemoveTablet in one call, effectively replacing the old tablet with the new.
	ReplaceTablet(old, new *topodata.Tablet)
}

TabletRecorder is a sub interface of HealthCheck. It is separated out to enable unit testing.

type TabletStatsList 

type TabletStatsList []*TabletHealth

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.

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. When tablets are added / removed, it calls the LegacyTabletRecorder AddTablet / RemoveTablet interface appropriately.

func NewCellTabletsWatcher 

func NewCellTabletsWatcher(ctx context.Context, topoServer *topo.Server, tr TabletRecorder, f TabletFilter, cell string, refreshInterval time.Duration, refreshKnownTablets bool, topoReadConcurrency int) *TopologyWatcher

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

func NewTopologyWatcher 

func NewTopologyWatcher(ctx context.Context, topoServer *topo.Server, tr TabletRecorder, filter TabletFilter, cell string, refreshInterval time.Duration, refreshKnownTablets bool, topoReadConcurrency int, getTablets func(tw *TopologyWatcher) ([]*topodata.TabletAlias, error)) *TopologyWatcher

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

func (*TopologyWatcher) RefreshLag 

func (tw *TopologyWatcher) RefreshLag() time.Duration

RefreshLag returns the time since the last refresh

func (*TopologyWatcher) Start 

func (tw *TopologyWatcher) Start()

Start starts the topology watcher

func (*TopologyWatcher) Stop 

func (tw *TopologyWatcher) Stop()

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

func (*TopologyWatcher) TopoChecksum 

func (tw *TopologyWatcher) TopoChecksum() uint32

TopoChecksum returns the checksum of the current state of the topo

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