mirror of https://github.com/hashicorp/consul
118 lines
3.4 KiB
Go
118 lines
3.4 KiB
Go
package raft
|
|
|
|
import (
|
|
"sync/atomic"
|
|
)
|
|
|
|
// Observation is sent along the given channel to observers when an event occurs.
|
|
type Observation struct {
|
|
// Raft holds the Raft instance generating the observation.
|
|
Raft *Raft
|
|
// Data holds observation-specific data. Possible types are
|
|
// *RequestVoteRequest and RaftState.
|
|
Data interface{}
|
|
}
|
|
|
|
// nextObserverId is used to provide a unique ID for each observer to aid in
|
|
// deregistration.
|
|
var nextObserverID uint64
|
|
|
|
// FilterFn is a function that can be registered in order to filter observations.
|
|
// The function reports whether the observation should be included - if
|
|
// it returns false, the observation will be filtered out.
|
|
type FilterFn func(o *Observation) bool
|
|
|
|
// Observer describes what to do with a given observation.
|
|
type Observer struct {
|
|
// numObserved and numDropped are performance counters for this observer.
|
|
// 64 bit types must be 64 bit aligned to use with atomic operations on
|
|
// 32 bit platforms, so keep them at the top of the struct.
|
|
numObserved uint64
|
|
numDropped uint64
|
|
|
|
// channel receives observations.
|
|
channel chan Observation
|
|
|
|
// blocking, if true, will cause Raft to block when sending an observation
|
|
// to this observer. This should generally be set to false.
|
|
blocking bool
|
|
|
|
// filter will be called to determine if an observation should be sent to
|
|
// the channel.
|
|
filter FilterFn
|
|
|
|
// id is the ID of this observer in the Raft map.
|
|
id uint64
|
|
}
|
|
|
|
// NewObserver creates a new observer that can be registered
|
|
// to make observations on a Raft instance. Observations
|
|
// will be sent on the given channel if they satisfy the
|
|
// given filter.
|
|
//
|
|
// If blocking is true, the observer will block when it can't
|
|
// send on the channel, otherwise it may discard events.
|
|
func NewObserver(channel chan Observation, blocking bool, filter FilterFn) *Observer {
|
|
return &Observer{
|
|
channel: channel,
|
|
blocking: blocking,
|
|
filter: filter,
|
|
id: atomic.AddUint64(&nextObserverID, 1),
|
|
}
|
|
}
|
|
|
|
// GetNumObserved returns the number of observations.
|
|
func (or *Observer) GetNumObserved() uint64 {
|
|
return atomic.LoadUint64(&or.numObserved)
|
|
}
|
|
|
|
// GetNumDropped returns the number of dropped observations due to blocking.
|
|
func (or *Observer) GetNumDropped() uint64 {
|
|
return atomic.LoadUint64(&or.numDropped)
|
|
}
|
|
|
|
// RegisterObserver registers a new observer.
|
|
func (r *Raft) RegisterObserver(or *Observer) {
|
|
r.observersLock.Lock()
|
|
defer r.observersLock.Unlock()
|
|
r.observers[or.id] = or
|
|
}
|
|
|
|
// DeregisterObserver deregisters an observer.
|
|
func (r *Raft) DeregisterObserver(or *Observer) {
|
|
r.observersLock.Lock()
|
|
defer r.observersLock.Unlock()
|
|
delete(r.observers, or.id)
|
|
}
|
|
|
|
// observe sends an observation to every observer.
|
|
func (r *Raft) observe(o interface{}) {
|
|
// In general observers should not block. But in any case this isn't
|
|
// disastrous as we only hold a read lock, which merely prevents
|
|
// registration / deregistration of observers.
|
|
r.observersLock.RLock()
|
|
defer r.observersLock.RUnlock()
|
|
for _, or := range r.observers {
|
|
// It's wasteful to do this in the loop, but for the common case
|
|
// where there are no observers we won't create any objects.
|
|
ob := Observation{Raft: r, Data: o}
|
|
if or.filter != nil && !or.filter(&ob) {
|
|
continue
|
|
}
|
|
if or.channel == nil {
|
|
continue
|
|
}
|
|
if or.blocking {
|
|
or.channel <- ob
|
|
atomic.AddUint64(&or.numObserved, 1)
|
|
} else {
|
|
select {
|
|
case or.channel <- ob:
|
|
atomic.AddUint64(&or.numObserved, 1)
|
|
default:
|
|
atomic.AddUint64(&or.numDropped, 1)
|
|
}
|
|
}
|
|
}
|
|
}
|