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dispatcher.go
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dispatcher.go
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// (c) 2019-2020, Ava Labs, Inc. All rights reserved.
// See the file LICENSE for licensing terms.
package triggers
import (
"fmt"
"sync"
"github.com/ava-labs/avalanchego/ids"
"github.com/ava-labs/avalanchego/snow"
"github.com/ava-labs/avalanchego/utils/logging"
)
var _ snow.EventDispatcher = &EventDispatcher{}
type handler struct {
// Must implement at least one of Acceptor, Rejector, Issuer
handlerFunc interface{}
// If true and [handlerFunc] returns an error during a call to Accept,
// the chain this handler corresponds to will stop.
dieOnError bool
}
// EventDispatcher receives events from consensus and dispatches the events to triggers
type EventDispatcher struct {
lock sync.Mutex
log logging.Logger
// Chain ID --> Identifier --> handler
chainHandlers map[ids.ID]map[string]handler
handlers map[string]interface{}
}
// Initialize creates the EventDispatcher's initial values
func (ed *EventDispatcher) Initialize(log logging.Logger) {
ed.log = log
ed.chainHandlers = make(map[ids.ID]map[string]handler)
ed.handlers = make(map[string]interface{})
}
// Accept is called when a transaction or block is accepted.
// If the returned error is non-nil, the chain associated with [ctx] should shut
// down and not commit [container] or any other container to its database as accepted.
func (ed *EventDispatcher) Accept(ctx *snow.Context, containerID ids.ID, container []byte) error {
ed.lock.Lock()
defer ed.lock.Unlock()
for id, handler := range ed.handlers {
handler, ok := handler.(Acceptor)
if !ok {
continue
}
if err := handler.Accept(ctx, containerID, container); err != nil {
ed.log.Error("handler %s on chain %s errored while accepting %s: %s", id, ctx.ChainID, containerID, err)
}
}
events, exist := ed.chainHandlers[ctx.ChainID]
if !exist {
return nil
}
for id, handler := range events {
handlerFunc, ok := handler.handlerFunc.(Acceptor)
if !ok {
continue
}
if err := handlerFunc.Accept(ctx, containerID, container); err != nil {
ed.log.Error("handler %s on chain %s errored while accepting %s: %s", id, ctx.ChainID, containerID, err)
if handler.dieOnError {
return fmt.Errorf("handler %s on chain %s errored while accepting %s: %w", id, ctx.ChainID, containerID, err)
}
}
}
return nil
}
// Reject is called when a transaction or block is rejected
func (ed *EventDispatcher) Reject(ctx *snow.Context, containerID ids.ID, container []byte) error {
ed.lock.Lock()
defer ed.lock.Unlock()
for id, handler := range ed.handlers {
handler, ok := handler.(Rejector)
if !ok {
continue
}
if err := handler.Reject(ctx, containerID, container); err != nil {
ed.log.Error("unable to Reject on %s for chainID %s: %s", id, ctx.ChainID, err)
}
}
events, exist := ed.chainHandlers[ctx.ChainID]
if !exist {
return nil
}
for id, handler := range events {
handler, ok := handler.handlerFunc.(Rejector)
if !ok {
continue
}
if err := handler.Reject(ctx, containerID, container); err != nil {
ed.log.Error("unable to Reject on %s for chainID %s: %s", id, ctx.ChainID, err)
}
}
return nil
}
// Issue is called when a transaction or block is issued
func (ed *EventDispatcher) Issue(ctx *snow.Context, containerID ids.ID, container []byte) error {
ed.lock.Lock()
defer ed.lock.Unlock()
for id, handler := range ed.handlers {
handler, ok := handler.(Issuer)
if !ok {
continue
}
if err := handler.Issue(ctx, containerID, container); err != nil {
ed.log.Error("unable to Issue on %s for chainID %s: %s", id, ctx.ChainID, err)
}
}
events, exist := ed.chainHandlers[ctx.ChainID]
if !exist {
return nil
}
for id, handler := range events {
handler, ok := handler.handlerFunc.(Issuer)
if !ok {
continue
}
if err := handler.Issue(ctx, containerID, container); err != nil {
ed.log.Error("unable to Issue on %s for chainID %s: %s", id, ctx.ChainID, err)
}
}
return nil
}
// RegisterChain causes [handlerFunc] to be invoked every time a container is issued, accepted or rejected on chain [chainID].
// [handlerFunc] should implement at least one of Acceptor, Rejector, Issuer.
// If [dieOnError], chain [chainID] stops if [handler].Accept is invoked and returns a non-nil error.
func (ed *EventDispatcher) RegisterChain(chainID ids.ID, identifier string, handlerFunc interface{}, dieOnError bool) error {
ed.lock.Lock()
defer ed.lock.Unlock()
events, exist := ed.chainHandlers[chainID]
if !exist {
events = make(map[string]handler)
ed.chainHandlers[chainID] = events
}
if _, ok := events[identifier]; ok {
return fmt.Errorf("handler %s already exists on chain %s", identifier, chainID)
}
events[identifier] = handler{
handlerFunc: handlerFunc,
dieOnError: dieOnError,
}
return nil
}
// DeregisterChain removes a chain handler from the system
func (ed *EventDispatcher) DeregisterChain(chainID ids.ID, identifier string) error {
ed.lock.Lock()
defer ed.lock.Unlock()
events, exist := ed.chainHandlers[chainID]
if !exist {
return fmt.Errorf("chain %s has no handlers", chainID)
}
if _, ok := events[identifier]; !ok {
return fmt.Errorf("handler %s does not exist on chain %s", identifier, chainID)
}
if len(events) == 1 {
delete(ed.chainHandlers, chainID)
} else {
delete(events, identifier)
}
return nil
}
// Register places a new handler into the system
func (ed *EventDispatcher) Register(identifier string, handler interface{}) error {
ed.lock.Lock()
defer ed.lock.Unlock()
if _, exist := ed.handlers[identifier]; exist {
return fmt.Errorf("handler %s already exists", identifier)
}
ed.handlers[identifier] = handler
return nil
}
// Deregister removes a handler from the system
func (ed *EventDispatcher) Deregister(identifier string) error {
ed.lock.Lock()
defer ed.lock.Unlock()
if _, exist := ed.handlers[identifier]; !exist {
return fmt.Errorf("handler %s already exists", identifier)
}
delete(ed.handlers, identifier)
return nil
}