nodestate

Documentation

Index

• Variables
• type Field
• type FieldCallback
• type Flags
  • func MergeFlags(list ...Flags) Flags
  • func (a Flags) And(b Flags) Flags
  • func (a Flags) AndNot(b Flags) Flags
  • func (a Flags) Equals(b Flags) bool
  • func (a Flags) HasAll(b Flags) bool
  • func (a Flags) HasNone(b Flags) bool
  • func (a Flags) IsEmpty() bool
  • func (a Flags) Or(b Flags) Flags
  • func (f Flags) String() string
  • func (a Flags) Xor(b Flags) Flags
• type NodeStateMachine
  • func NewNodeStateMachine(db ctxcdb.KeyValueStore, dbKey []byte, clock mclock.Clock, setup *Setup) *NodeStateMachine
  • func (ns *NodeStateMachine) AddLogMetrics(requireFlags, disableFlags Flags, name string, inMeter, outMeter metrics.Meter, ...)
  • func (ns *NodeStateMachine) AddTimeout(n *enode.Node, flags Flags, timeout time.Duration) error
  • func (ns *NodeStateMachine) ForEach(requireFlags, disableFlags Flags, cb func(n *enode.Node, state Flags))
  • func (ns *NodeStateMachine) GetField(n *enode.Node, field Field) interface{}
  • func (ns *NodeStateMachine) GetNode(id enode.ID) *enode.Node
  • func (ns *NodeStateMachine) Operation(fn func()) error
  • func (ns *NodeStateMachine) Persist(n *enode.Node) error
  • func (ns *NodeStateMachine) SetField(n *enode.Node, field Field, value interface{}) error
  • func (ns *NodeStateMachine) SetFieldSub(n *enode.Node, field Field, value interface{}) error
  • func (ns *NodeStateMachine) SetState(n *enode.Node, setFlags, resetFlags Flags, timeout time.Duration) error
  • func (ns *NodeStateMachine) SetStateSub(n *enode.Node, setFlags, resetFlags Flags, timeout time.Duration)
  • func (ns *NodeStateMachine) Start()
  • func (ns *NodeStateMachine) Stop()
  • func (ns *NodeStateMachine) SubscribeField(field Field, callback FieldCallback)
  • func (ns *NodeStateMachine) SubscribeState(flags Flags, callback StateCallback)
• type Setup
  • func (s *Setup) NewField(name string, ftype reflect.Type) Field
  • func (s *Setup) NewFlag(name string) Flags
  • func (s *Setup) NewPersistentField(name string, ftype reflect.Type, encode func(interface{}) ([]byte, error), ...) Field
  • func (s *Setup) NewPersistentFlag(name string) Flags
  • func (s *Setup) OfflineFlag() Flags
• type StateCallback

Variables

var (
	ErrInvalidField = errors.New("invalid field type")
	ErrClosed       = errors.New("already closed")
)

Types

type Field

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

Field represents a field from a certain setup

type FieldCallback

type FieldCallback func(n *enode.Node, state Flags, oldValue, newValue interface{})

FieldCallback is a subscription callback which is called when the value of a specific field is changed.

type Flags

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

Flags represents a set of flags from a certain setup

func MergeFlags

func MergeFlags(list ...Flags) Flags

MergeFlags merges multiple sets of state flags

func (Flags) And

func (a Flags) And(b Flags) Flags

And returns the set of flags present in both a and b

func (Flags) AndNot

func (a Flags) AndNot(b Flags) Flags

AndNot returns the set of flags present in a but not in b

func (Flags) Equals

func (a Flags) Equals(b Flags) bool

Equals returns true if a and b have the same flags set

func (Flags) HasAll

func (a Flags) HasAll(b Flags) bool

HasAll returns true if b is a subset of a

func (Flags) HasNone

func (a Flags) HasNone(b Flags) bool

HasNone returns true if a and b have no shared flags

func (Flags) IsEmpty

func (a Flags) IsEmpty() bool

IsEmpty returns true if a has no flags set

func (Flags) Or

func (a Flags) Or(b Flags) Flags

Or returns the set of flags present in either a or b

func (Flags) String

func (f Flags) String() string

String returns a list of the names of the flags specified in the bit mask

func (Flags) Xor

func (a Flags) Xor(b Flags) Flags

Xor returns the set of flags present in either a or b but not both

type NodeStateMachine

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

NodeStateMachine implements a network node-related event subscription system. It can assign binary state flags and fields of arbitrary type to each node and allows subscriptions to flag/field changes which can also modify further flags and fields, potentially triggering further subscriptions. An operation includes an initial change and all resulting subsequent changes and always ends in a consistent global state. It is initiated by a "top level" SetState/SetField call that blocks (also blocking other top-level functions) until the operation is finished. Callbacks making further changes should use the non-blocking SetStateSub/SetFieldSub functions. The tree of events resulting from the initial changes is traversed in a breadth-first order, ensuring for each subscription callback that all other callbacks caused by the same change triggering the current callback are processed before anything is triggered by the changes made in the current callback. In practice this logic ensures that all subscriptions "see" events in the logical order, callbacks are never called concurrently and "back and forth" effects are also possible. The state machine design should ensure that infinite event cycles cannot happen. The caller can also add timeouts assigned to a certain node and a subset of state flags. If the timeout elapses, the flags are reset. If all relevant flags are reset then the timer is dropped. State flags with no timeout are persisted in the database if the flag descriptor enables saving. If a node has no state flags set at any moment then it is discarded. Note: in order to avoid mutex deadlocks the callbacks should never lock a mutex that might be locked when the top level SetState/SetField functions are called. If a function potentially performs state/field changes then it is recommended to mention this fact in the function description, along with whether it should run inside an operation callback.

func NewNodeStateMachine

func NewNodeStateMachine(db ctxcdb.KeyValueStore, dbKey []byte, clock mclock.Clock, setup *Setup) *NodeStateMachine

NewNodeStateMachine creates a new node state machine. If db is not nil then the node states, fields and active timeouts are persisted. Persistence can be enabled or disabled for each state flag and field.

func (*NodeStateMachine) AddLogMetrics

func (ns *NodeStateMachine) AddLogMetrics(requireFlags, disableFlags Flags, name string, inMeter, outMeter metrics.Meter, gauge metrics.Gauge)

AddLogMetrics adds logging and/or metrics for nodes entering, exiting and currently being in a given set specified by required and disabled state flags

func (*NodeStateMachine) AddTimeout

func (ns *NodeStateMachine) AddTimeout(n *enode.Node, flags Flags, timeout time.Duration) error

AddTimeout adds a node state timeout associated to the given state flag(s). After the specified time interval, the relevant states will be reset.

func (*NodeStateMachine) ForEach

func (ns *NodeStateMachine) ForEach(requireFlags, disableFlags Flags, cb func(n *enode.Node, state Flags))

ForEach calls the callback for each node having all of the required and none of the disabled flags set. Note that this callback is not an operation callback but ForEach can be called from an Operation callback or Operation can also be called from a ForEach callback if necessary.

func (*NodeStateMachine) GetField

func (ns *NodeStateMachine) GetField(n *enode.Node, field Field) interface{}

GetField retrieves the given field of the given node. Note that when used in a subscription callback the result can be out of sync with the state change represented by the callback parameters so extra safety checks might be necessary.

func (*NodeStateMachine) GetNode

func (ns *NodeStateMachine) GetNode(id enode.ID) *enode.Node

GetNode returns the enode currently associated with the given ID

func (*NodeStateMachine) Operation

func (ns *NodeStateMachine) Operation(fn func()) error

Operation calls the given function as an operation callback. This allows the caller to start an operation with multiple initial changes. The same rules apply as for subscription callbacks.

func (*NodeStateMachine) Persist

func (ns *NodeStateMachine) Persist(n *enode.Node) error

Persist saves the persistent state and fields of the given node immediately

func (*NodeStateMachine) SetField

func (ns *NodeStateMachine) SetField(n *enode.Node, field Field, value interface{}) error

SetField sets the given field of the given node and blocks until the operation is finished

func (*NodeStateMachine) SetFieldSub

func (ns *NodeStateMachine) SetFieldSub(n *enode.Node, field Field, value interface{}) error

SetFieldSub sets the given field of the given node without blocking (should be called from a subscription/operation callback).

func (*NodeStateMachine) SetState

func (ns *NodeStateMachine) SetState(n *enode.Node, setFlags, resetFlags Flags, timeout time.Duration) error

SetState updates the given node state flags and blocks until the operation is finished. If a flag with a timeout is set again, the operation removes or replaces the existing timeout.

func (*NodeStateMachine) SetStateSub

func (ns *NodeStateMachine) SetStateSub(n *enode.Node, setFlags, resetFlags Flags, timeout time.Duration)

SetStateSub updates the given node state flags without blocking (should be called from a subscription/operation callback).

func (*NodeStateMachine) Start

func (ns *NodeStateMachine) Start()

Start starts the state machine, enabling state and field operations and disabling further subscriptions.

func (*NodeStateMachine) Stop

func (ns *NodeStateMachine) Stop()

Stop stops the state machine and saves its state if a database was supplied

func (*NodeStateMachine) SubscribeField

func (ns *NodeStateMachine) SubscribeField(field Field, callback FieldCallback)

SubscribeField adds a node field subscription. Same rules apply as for SubscribeState.

func (*NodeStateMachine) SubscribeState

func (ns *NodeStateMachine) SubscribeState(flags Flags, callback StateCallback)

SubscribeState adds a node state subscription. The callback is called while the state machine mutex is not held and it is allowed to make further state updates using the non-blocking SetStateSub/SetFieldSub functions. All callbacks of an operation are running from the thread/goroutine of the initial caller and parallel operations are not permitted. Therefore the callback is never called concurrently. It is the responsibility of the implemented state logic to avoid deadlocks and to reach a stable state in a finite amount of steps. State subscriptions should be installed before loading the node database or making the first state update.

type Setup

type Setup struct {
	Version uint
	// contains filtered or unexported fields
}

stateSetup contains the list of flags and fields used by the application

func (*Setup) NewField

func (s *Setup) NewField(name string, ftype reflect.Type) Field

NewField creates a new node state field

func (*Setup) NewFlag

func (s *Setup) NewFlag(name string) Flags

NewFlag creates a new node state flag

func (*Setup) NewPersistentField

func (s *Setup) NewPersistentField(name string, ftype reflect.Type, encode func(interface{}) ([]byte, error), decode func([]byte) (interface{}, error)) Field

NewPersistentField creates a new persistent node field

func (*Setup) NewPersistentFlag

func (s *Setup) NewPersistentFlag(name string) Flags

NewPersistentFlag creates a new persistent node state flag

func (*Setup) OfflineFlag

func (s *Setup) OfflineFlag() Flags

OfflineFlag returns the system-defined offline flag belonging to the given setup

type StateCallback

type StateCallback func(n *enode.Node, oldState, newState Flags)

StateCallback is a subscription callback which is called when one of the state flags that is included in the subscription state mask is changed. Note: oldState and newState are also masked with the subscription mask so only the relevant bits are included.