cluster

package
v0.0.0-...-560f09a Latest Latest
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 Go to latest Published: Oct 18, 2023 License: AGPL-3.0 Imports: 14 Imported by: 0

Documentation

Index

Constants

View Source 
const (
	ElectionPrefix  = "election"
	StateDataPrefix = "state-data"
	NodesPrefix     = "nodes"
)

Variables

View Source 
var (
	ErrClusterTickDisagreement = errors.New("cluster tick disagreement")
	ErrNoLease                 = errors.New("no lease")
)

Functions

This section is empty.

Types

type ClusterNode 

type ClusterNode struct {
	ID          int64
	Address     string
	Role        NodeRole
	Ttl         time.Duration
	ClusterName string
	StartTime   time.Time
	// contains filtered or unexported fields
}

ClusterNode 

ClusterNode in a distributed cluster capable of
handling leader elections

func NewClusterNode 

func NewClusterNode(opts ClusterNodeOptions) (*ClusterNode, error)

NewClusterNode 

Creates a new cluster node with a connection to the etcd cluster.

func (*ClusterNode) Close 

func (n *ClusterNode) Close() error

Close 

Closes the node and its connection to the etcd cluster.
A closed node cannot be restarted.

func (*ClusterNode) Delete 

func (n *ClusterNode) Delete(key string) error

Delete 

Removes the value associated with a given key from
the cluster correlated to the node. If the key does
not exist, the method will return nil.

func (*ClusterNode) Get 

func (n *ClusterNode) Get(key string) (string, error)

Get 

Retrieves the value associated with a given key from
the cluster correlated to the node. If the key does
not exist, the method will return an empty string.

func (*ClusterNode) GetAsNode 

func (n *ClusterNode) GetAsNode(nodeId int64, key string) (string, error)

GetAsNode 

Retrieves the value associated with a given key from
the cluster correlated to the passed node id. If the
key does not exist, the method will return an empty
string.

func (*ClusterNode) GetCluster 

func (n *ClusterNode) GetCluster(key string) (map[int64][]KV, error)

GetCluster 

Retrieves the values associated with a given prefix for
all nodes in the cluster and returns the values in a
map where each key is the node's id and the value is
the value associated with that node.

Every node in the cluster will return a key in the map.
If a node does not have a value for the key the value
will be an empty string for that node's id.

func (*ClusterNode) GetLeader 

func (n *ClusterNode) GetLeader() (int64, error)

GetLeader 

Retrieves the current leader for the cluster. Returns
-1 if there is currently no leader for the cluster.

func (*ClusterNode) GetNodeMetadata 

func (n *ClusterNode) GetNodeMetadata(id int64) (*NodeMetadata, error)

GetNodeMetadata 

Returns the specified node's metadata

func (*ClusterNode) GetNodes 

func (n *ClusterNode) GetNodes() ([]NodeMetadata, error)

GetNodes 

Retrieves all the nodes in the cluster.

func (*ClusterNode) GetSelfMetadata 

func (n *ClusterNode) GetSelfMetadata() NodeMetadata

GetSelfMetadata 

Returns the called node's metadata

func (*ClusterNode) Put 

func (n *ClusterNode) Put(key string, value string) error

Put 

Adds a new key-value pair to the cluster that is bound
to the node. If the node times out, the key-value pair
will be dropped from the cluster. If the key already
exists, it will be overwritten.

func (*ClusterNode) Start 

func (n *ClusterNode) Start()

Start 

Initiate a connection to the etcd cluster and
begin campaigning to become leader. Once a role
in the cluster has been established, the node
begins its work as a leader or follower in the
background.

func (*ClusterNode) Stop 

func (n *ClusterNode) Stop()

Stop 

Stops an active node within the cluster gracefully.
The node will cease all participation in the cluster
at its earliest convenience. If the node is a leader,
it will resign its position as leader before stopping.
Stopping removes the node from the cluster but preserves
the connection to the etcd cluster such that the node
can be started again.

func (*ClusterNode) WatchKeyCluster 

func (n *ClusterNode) WatchKeyCluster(ctx context.Context, key string) (chan StateChangeEvent, error)

WatchKeyCluster 

Watches to changes for a particular key in any of the
nodes in the cluster.

type ClusterNodeOptions 

type ClusterNodeOptions struct {
	Ctx             context.Context
	ID              int64
	Address         string
	Ttl             time.Duration
	ClusterName     string
	EtcdConfig      etcd.Config
	LeaderRoutine   LeaderRoutine
	FollowerRoutine FollowerRoutine
	RoutineTick     time.Duration
	Logger          logging.Logger
}

ClusterNodeOptions 

Options for a cluster node

type EventType 

type EventType int

EventType 

Type of event that occurred to the state

const (
	// EventTypeAdded value has been added to the state and previously did not exist
	EventTypeAdded EventType = iota
	// EventTypeModified value has been modified in the state and previously existed
	EventTypeModified
	// EventTypeDeleted value has been removed from the state and previously existed
	EventTypeDeleted
)

func (EventType) String 

func (t EventType) String() string

type FollowerRoutine 

type FollowerRoutine func(ctx context.Context) error

FollowerRoutine 

Called by the follower every 50ms. The function should
exit as quickly as possible on a context cancel and
encompass an entire execution cycle for the follower.
Any logic container in this function that should not
be executed as frequently as 50ms should track the time
between executions independently and skip cycles that
are not appropriate for such logic.

type KV 

type KV struct {
	Key   string
	Value string
}

KV

Simple key-value pair

type LeaderRoutine 

type LeaderRoutine func(ctx context.Context) error

LeaderRoutine 

Called by the leader every 50ms. The function should
exit as quickly as possible on a context cancel and
encompass an entire execution cycle for the leader.
Any logic container in this function that should not
be executed as frequently as 50ms should track the time
between executions independently and skip cycles that
are not appropriate for such logic.

type Node 

type Node interface {
	// Start
	//
	//  Initiate a connection to the etcd cluster and
	//  begin campaigning to become leader. Once a role
	//  in the cluster has been established, the node
	//  begins its work as a leader or follower in the
	//  background.
	Start()

	// Stop
	//
	//  Stops an active node within the cluster gracefully.
	//  The node will cease all participation in the cluster
	//  at its earliest convenience. If the node is a leader,
	//  it will resign its position as leader before stopping.
	//  Stopping removes the node from the cluster but preserves
	//  the connection to the etcd cluster such that the node
	//  can be started again.
	Stop()

	// Close
	//
	//  Closes the node and its connection to the etcd cluster.
	//  A closed node cannot be restarted.
	Close() error

	// Put
	//
	//  Adds a new key-value pair to the cluster that is bound
	//  to the node. If the node times out, the key-value pair
	//  will be dropped from the cluster. If the key already
	//  exists, it will be overwritten.
	Put(key string, value string) error

	// Get
	//
	//  Retrieves the value associated with a given key from
	//  the cluster correlated to the node. If the key does
	//  not exist, the method will return an empty string.
	Get(key string) (string, error)

	// GetAsNode
	//
	//  Retrieves the value associated with a given key from
	//  the cluster correlated to the passed node id. If the
	//  key does not exist, the method will return an empty
	//  string.
	GetAsNode(nodeId int64, key string) (string, error)

	// GetCluster
	//
	//  Retrieves the values associated with a given prefix for
	//  all nodes in the cluster and returns the values in a
	//  map where each key is the node's id and the value is
	//  a slice of key value pairs found with passed prefix
	//  for the node with the node id stripped from the key.
	//
	//  Every node in the cluster will return a key in the map.
	//  If a node does not have a value for the key the value
	//  will be an empty slice for that node's id.
	GetCluster(key string) (map[int64][]KV, error)

	// Delete
	//
	//  Removes the value associated with a given key from
	//  the cluster correlated to the node. If the key does
	//  not exist, the method will return nil.
	Delete(key string) error

	// WatchKeyCluster
	//
	//  Watches to changes for a particular key in any of the
	//  nodes in the cluster.
	WatchKeyCluster(ctx context.Context, key string) (chan StateChangeEvent, error)

	// GetNodes
	//
	//  Retrieves all the nodes in the cluster.
	GetNodes() ([]NodeMetadata, error)

	// GetLeader
	//
	//  Retrieves the current leader for the cluster. Returns
	//  -1 if there is currently no leader for the cluster.
	GetLeader() (int64, error)

	// GetSelfMetadata
	//
	//  Returns the called node's metadata
	GetSelfMetadata() NodeMetadata

	// GetNodeMetadata
	//
	//  Returns the specified node's metadata and nil if the node is not found
	GetNodeMetadata(id int64) (*NodeMetadata, error)
}

Node 

Interface to interact with a cluster node

type NodeMetadata 

type NodeMetadata struct {
	ID      int64
	Address string
	Start   time.Time
	Role    NodeRole
}

NodeMetadata 

Metadata for a node that is persisted in the cluster state

func UnmarshalNodeMetadata 

func UnmarshalNodeMetadata(data []byte) (NodeMetadata, error)

func (*NodeMetadata) Marshal 

func (m *NodeMetadata) Marshal() ([]byte, error)

type NodeRole 

type NodeRole int
const (
	NodeRoleUnknown NodeRole = iota
	NodeRoleLeader
	NodeRoleFollower
)

func (NodeRole) String 

func (s NodeRole) String() string

type StandaloneNode 

type StandaloneNode struct {
	ID        int64
	Address   string
	StartTime time.Time
	Role      NodeRole
	// contains filtered or unexported fields
}

StandaloneNode 

StandaloneNode mocks the Node interface but executes the roles of
leader and follower itself

func NewStandaloneNode 

func NewStandaloneNode(ctx context.Context, id int64, address string, leaderRoutine LeaderRoutine,
	followerRoutine FollowerRoutine, tick time.Duration, logger logging.Logger) *StandaloneNode

NewStandaloneNode 

Creates a new StandaloneNode

func (*StandaloneNode) Close 

func (n *StandaloneNode) Close() error

Close 

Closes the StandaloneNode
This function is a no-op but is needed to satisfy the Node interface

func (*StandaloneNode) Delete 

func (n *StandaloneNode) Delete(key string) error

Delete 

Removes the value associated with a given key from
the cluster correlated to the node. If the key does
not exist, the method will return nil.

func (*StandaloneNode) Get 

func (n *StandaloneNode) Get(key string) (string, error)

Get 

Retrieves the value associated with a given key from
the cluster correlated to the node. If the key does
not exist, the method will return an empty string.

func (*StandaloneNode) GetAsNode 

func (n *StandaloneNode) GetAsNode(nodeId int64, key string) (string, error)

GetAsNode 

	This is a compliance function for the Node interface.
 The function will operate the same as Get when provided
 with the self-id of the node instance and will return an
 empty string for any other id.

func (*StandaloneNode) GetCluster 

func (n *StandaloneNode) GetCluster(key string) (map[int64][]KV, error)

GetCluster 

Retrieves the values associated with a given prefix for
all nodes in the cluster and returns the values in a
map where each key is the node's id and the value is
a slice of key value pairs found with passed prefix
for the node with the node id stripped from the key.

Every node in the cluster will return a key in the map.
If a node does not have a value for the key the value
will be an empty slice for that node's id.

func (*StandaloneNode) GetLeader 

func (n *StandaloneNode) GetLeader() (int64, error)

GetLeader 

Retrieves the current leader for the cluster. Returns
-1 if there is currently no leader for the cluster.

func (*StandaloneNode) GetNodeMetadata 

func (n *StandaloneNode) GetNodeMetadata(id int64) (*NodeMetadata, error)

GetNodeMetadata 

Returns the specified node's metadata and nil if the node is not found

func (*StandaloneNode) GetNodes 

func (n *StandaloneNode) GetNodes() ([]NodeMetadata, error)

GetNodes 

Retrieves all the nodes in the cluster.

func (*StandaloneNode) GetSelfMetadata 

func (n *StandaloneNode) GetSelfMetadata() NodeMetadata

GetSelfMetadata 

Returns the called node's metadata

func (*StandaloneNode) Put 

func (n *StandaloneNode) Put(key string, value string) error

Put 

Adds a new key-value pair to the cluster that is bound
to the node. If the node times out, the key-value pair
will be dropped from the cluster. If the key already
exists, it will be overwritten.

func (*StandaloneNode) Start 

func (n *StandaloneNode) Start()

Start 

Starts the StandaloneNode

func (*StandaloneNode) Stop 

func (n *StandaloneNode) Stop()

Stop 

Stops the StandaloneNode

func (*StandaloneNode) WatchKeyCluster 

func (n *StandaloneNode) WatchKeyCluster(ctx context.Context, key string) (chan StateChangeEvent, error)

WatchKeyCluster 

Watches to changes for a particular key in any of the
nodes in the cluster.

type StateChangeEvent 

type StateChangeEvent struct {
	Type     EventType
	NodeID   int64
	Key      string
	Value    string
	OldKey   string
	OldValue string
}

StateChangeEvent 

An event in which the state of state kv pair changes

Source Files

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