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node_fsm.go
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node_fsm.go
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package client
import (
"fmt"
"math/big"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/promauto"
)
var (
promPoolRPCNodeTransitionsToAlive = promauto.NewCounterVec(prometheus.CounterOpts{
Name: "pool_rpc_node_num_transitions_to_alive",
Help: transitionString(nodeStateAlive),
}, []string{"chainID", "nodeName"})
promPoolRPCNodeTransitionsToInSync = promauto.NewCounterVec(prometheus.CounterOpts{
Name: "pool_rpc_node_num_transitions_to_in_sync",
Help: fmt.Sprintf("%s to %s", transitionString(nodeStateOutOfSync), nodeStateAlive),
}, []string{"chainID", "nodeName"})
promPoolRPCNodeTransitionsToOutOfSync = promauto.NewCounterVec(prometheus.CounterOpts{
Name: "pool_rpc_node_num_transitions_to_out_of_sync",
Help: transitionString(nodeStateOutOfSync),
}, []string{"chainID", "nodeName"})
promPoolRPCNodeTransitionsToUnreachable = promauto.NewCounterVec(prometheus.CounterOpts{
Name: "pool_rpc_node_num_transitions_to_unreachable",
Help: transitionString(nodeStateUnreachable),
}, []string{"chainID", "nodeName"})
promPoolRPCNodeTransitionsToInvalidChainID = promauto.NewCounterVec(prometheus.CounterOpts{
Name: "pool_rpc_node_num_transitions_to_invalid_chain_id",
Help: transitionString(nodeStateInvalidChainID),
}, []string{"chainID", "nodeName"})
promPoolRPCNodeTransitionsToUnusable = promauto.NewCounterVec(prometheus.CounterOpts{
Name: "pool_rpc_node_num_transitions_to_unusable",
Help: transitionString(nodeStateUnusable),
}, []string{"chainID", "nodeName"})
)
// nodeState represents the current state of the node
// Node is a FSM (finite state machine)
type nodeState int
func (n nodeState) String() string {
switch n {
case nodeStateUndialed:
return "Undialed"
case nodeStateDialed:
return "Dialed"
case nodeStateInvalidChainID:
return "InvalidChainID"
case nodeStateAlive:
return "Alive"
case nodeStateUnreachable:
return "Unreachable"
case nodeStateUnusable:
return "Unusable"
case nodeStateOutOfSync:
return "OutOfSync"
case nodeStateClosed:
return "Closed"
default:
return fmt.Sprintf("nodeState(%d)", n)
}
}
// GoString prints a prettier state
func (n nodeState) GoString() string {
return fmt.Sprintf("nodeState%s(%d)", n.String(), n)
}
const (
// nodeStateUndialed is the first state of a virgin node
nodeStateUndialed = nodeState(iota)
// nodeStateDialed is after a node has successfully dialed but before it has verified the correct chain ID
nodeStateDialed
// nodeStateInvalidChainID is after chain ID verification failed
nodeStateInvalidChainID
// nodeStateAlive is a healthy node after chain ID verification succeeded
nodeStateAlive
// nodeStateUnreachable is a node that cannot be dialed or has disconnected
nodeStateUnreachable
// nodeStateOutOfSync is a node that is accepting connections but exceeded
// the failure threshold without sending any new heads. It will be
// disconnected, then put into a revive loop and re-awakened after redial
// if a new head arrives
nodeStateOutOfSync
// nodeStateUnusable is a sendonly node that has an invalid URL that can never be reached
nodeStateUnusable
// nodeStateClosed is after the connection has been closed and the node is at the end of its lifecycle
nodeStateClosed
// nodeStateLen tracks the number of states
nodeStateLen
)
// allNodeStates represents all possible states a node can be in
var allNodeStates []nodeState
func init() {
for s := nodeState(0); s < nodeStateLen; s++ {
allNodeStates = append(allNodeStates, s)
}
}
// FSM methods
// State allows reading the current state of the node.
func (n *node[CHAIN_ID, HEAD, RPC]) State() nodeState {
n.stateMu.RLock()
defer n.stateMu.RUnlock()
return n.state
}
func (n *node[CHAIN_ID, HEAD, RPC]) StateAndLatest() (nodeState, int64, *big.Int) {
n.stateMu.RLock()
defer n.stateMu.RUnlock()
return n.state, n.stateLatestBlockNumber, n.stateLatestTotalDifficulty
}
// setState is only used by internal state management methods.
// This is low-level; care should be taken by the caller to ensure the new state is a valid transition.
// State changes should always be synchronous: only one goroutine at a time should change state.
// n.stateMu should not be locked for long periods of time because external clients expect a timely response from n.State()
func (n *node[CHAIN_ID, HEAD, RPC]) setState(s nodeState) {
n.stateMu.Lock()
defer n.stateMu.Unlock()
n.state = s
}
// declareXXX methods change the state and pass conrol off the new state
// management goroutine
func (n *node[CHAIN_ID, HEAD, RPC]) declareAlive() {
n.transitionToAlive(func() {
n.lfcLog.Infow("RPC Node is online", "nodeState", n.state)
n.wg.Add(1)
go n.aliveLoop()
})
}
func (n *node[CHAIN_ID, HEAD, RPC]) transitionToAlive(fn func()) {
promPoolRPCNodeTransitionsToAlive.WithLabelValues(n.chainID.String(), n.name).Inc()
n.stateMu.Lock()
defer n.stateMu.Unlock()
if n.state == nodeStateClosed {
return
}
switch n.state {
case nodeStateDialed, nodeStateInvalidChainID:
n.state = nodeStateAlive
default:
panic(transitionFail(n.state, nodeStateAlive))
}
fn()
}
// declareInSync puts a node back into Alive state, allowing it to be used by
// pool consumers again
func (n *node[CHAIN_ID, HEAD, RPC]) declareInSync() {
n.transitionToInSync(func() {
n.lfcLog.Infow("RPC Node is back in sync", "nodeState", n.state)
n.wg.Add(1)
go n.aliveLoop()
})
}
func (n *node[CHAIN_ID, HEAD, RPC]) transitionToInSync(fn func()) {
promPoolRPCNodeTransitionsToAlive.WithLabelValues(n.chainID.String(), n.name).Inc()
promPoolRPCNodeTransitionsToInSync.WithLabelValues(n.chainID.String(), n.name).Inc()
n.stateMu.Lock()
defer n.stateMu.Unlock()
if n.state == nodeStateClosed {
return
}
switch n.state {
case nodeStateOutOfSync:
n.state = nodeStateAlive
default:
panic(transitionFail(n.state, nodeStateAlive))
}
fn()
}
// declareOutOfSync puts a node into OutOfSync state, disconnecting all current
// clients and making it unavailable for use until back in-sync.
func (n *node[CHAIN_ID, HEAD, RPC]) declareOutOfSync(isOutOfSync func(num int64, td *big.Int) bool) {
n.transitionToOutOfSync(func() {
n.lfcLog.Errorw("RPC Node is out of sync", "nodeState", n.state)
n.wg.Add(1)
go n.outOfSyncLoop(isOutOfSync)
})
}
func (n *node[CHAIN_ID, HEAD, RPC]) transitionToOutOfSync(fn func()) {
promPoolRPCNodeTransitionsToOutOfSync.WithLabelValues(n.chainID.String(), n.name).Inc()
n.stateMu.Lock()
defer n.stateMu.Unlock()
if n.state == nodeStateClosed {
return
}
switch n.state {
case nodeStateAlive:
n.disconnectAll()
n.state = nodeStateOutOfSync
default:
panic(transitionFail(n.state, nodeStateOutOfSync))
}
fn()
}
func (n *node[CHAIN_ID, HEAD, RPC]) declareUnreachable() {
n.transitionToUnreachable(func() {
n.lfcLog.Errorw("RPC Node is unreachable", "nodeState", n.state)
n.wg.Add(1)
go n.unreachableLoop()
})
}
func (n *node[CHAIN_ID, HEAD, RPC]) transitionToUnreachable(fn func()) {
promPoolRPCNodeTransitionsToUnreachable.WithLabelValues(n.chainID.String(), n.name).Inc()
n.stateMu.Lock()
defer n.stateMu.Unlock()
if n.state == nodeStateClosed {
return
}
switch n.state {
case nodeStateUndialed, nodeStateDialed, nodeStateAlive, nodeStateOutOfSync, nodeStateInvalidChainID:
n.disconnectAll()
n.state = nodeStateUnreachable
default:
panic(transitionFail(n.state, nodeStateUnreachable))
}
fn()
}
func (n *node[CHAIN_ID, HEAD, RPC]) declareInvalidChainID() {
n.transitionToInvalidChainID(func() {
n.lfcLog.Errorw("RPC Node has the wrong chain ID", "nodeState", n.state)
n.wg.Add(1)
go n.invalidChainIDLoop()
})
}
func (n *node[CHAIN_ID, HEAD, RPC]) transitionToInvalidChainID(fn func()) {
promPoolRPCNodeTransitionsToInvalidChainID.WithLabelValues(n.chainID.String(), n.name).Inc()
n.stateMu.Lock()
defer n.stateMu.Unlock()
if n.state == nodeStateClosed {
return
}
switch n.state {
case nodeStateDialed, nodeStateOutOfSync:
n.disconnectAll()
n.state = nodeStateInvalidChainID
default:
panic(transitionFail(n.state, nodeStateInvalidChainID))
}
fn()
}
func transitionString(state nodeState) string {
return fmt.Sprintf("Total number of times node has transitioned to %s", state)
}
func transitionFail(from nodeState, to nodeState) string {
return fmt.Sprintf("cannot transition from %#v to %#v", from, to)
}