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engine.go
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engine.go
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package splitter
import (
"fmt"
"sync"
"github.com/hashicorp/go-multierror"
"github.com/rs/zerolog"
"github.com/onflow/flow-go/engine"
"github.com/onflow/flow-go/model/flow"
"github.com/onflow/flow-go/network"
"github.com/onflow/flow-go/network/channels"
)
// Engine is the splitter engine, which maintains a list of registered engines
// and passes every event it receives to each of these engines in parallel.
type Engine struct {
enginesMu sync.RWMutex
unit *engine.Unit // used to manage concurrency & shutdown
log zerolog.Logger // used to log relevant actions with context
engines map[network.MessageProcessor]struct{} // stores registered engines
channel channels.Channel // the channel that this splitter listens on
}
// New creates a new splitter engine.
func New(
log zerolog.Logger,
channel channels.Channel,
) *Engine {
return &Engine{
unit: engine.NewUnit(),
log: log.With().Str("engine", "splitter").Logger(),
engines: make(map[network.MessageProcessor]struct{}),
channel: channel,
}
}
// RegisterEngine registers a new engine with the splitter. Events
// that are received by the splitter after the engine has registered
// will be passed down to it.
func (e *Engine) RegisterEngine(engine network.MessageProcessor) {
e.enginesMu.Lock()
defer e.enginesMu.Unlock()
e.engines[engine] = struct{}{}
}
// UnregisterEngine unregisters an engine with the splitter. After
// the engine has been unregistered, the splitter will stop passing
// events to it. If the given engine was never registered, this is
// a noop.
func (e *Engine) UnregisterEngine(engine network.MessageProcessor) {
e.enginesMu.Lock()
defer e.enginesMu.Unlock()
delete(e.engines, engine)
}
// Ready returns a ready channel that is closed once the engine has fully
// started.
func (e *Engine) Ready() <-chan struct{} {
return e.unit.Ready()
}
// Done returns a done channel that is closed once the engine has fully stopped.
func (e *Engine) Done() <-chan struct{} {
return e.unit.Done()
}
// Process processes the given event from the node with the given origin ID
// in a blocking manner. It returns the potential processing error when
// done.
func (e *Engine) Process(channel channels.Channel, originID flow.Identifier, event interface{}) error {
return e.unit.Do(func() error {
if channel != e.channel {
return fmt.Errorf("received event on unknown channel %s", channel)
}
return e.process(func(downstream network.MessageProcessor) error {
return downstream.Process(channel, originID, event)
})
})
}
// process calls the given function in parallel for all the engines that have
// registered with this splitter.
func (e *Engine) process(processFunc func(network.MessageProcessor) error) error {
count := 0
errors := make(chan error)
e.enginesMu.RLock()
for eng := range e.engines {
e.enginesMu.RUnlock()
count += 1
go func(downstream network.MessageProcessor) {
errors <- processFunc(downstream)
}(eng)
e.enginesMu.RLock()
}
e.enginesMu.RUnlock()
var multiErr *multierror.Error
for i := 0; i < count; i++ {
multiErr = multierror.Append(multiErr, <-errors)
}
return multiErr.ErrorOrNil()
}