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info.go
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/
info.go
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// Copyright 2018 Anapaya Systems
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package discoveryinfo
import (
"fmt"
"math"
"sync"
"time"
"github.com/scionproto/scion/go/lib/addr"
"github.com/scionproto/scion/go/lib/discovery"
)
const (
// failExpStart is the time after which fails are expired.
failExpStart = 5 * time.Minute
// failExpInterval is the interval between fail expiration.
failExpInterval = 10 * time.Second
)
var _ discovery.InstanceInfo = (*Info)(nil)
// Info keeps track of the discovery service and its health.
type Info struct {
mu sync.Mutex
addr *addr.AppAddr
key string
lastFail time.Time
lastExp time.Time
failCount uint16
}
// New creates a new info with the specified key and address.
func New(key string, addr *addr.AppAddr) *Info {
return &Info{
addr: addr,
key: key,
lastFail: time.Now(),
lastExp: time.Now(),
}
}
// Update updates the address. If changed, the fail count is reset.
func (h *Info) Update(a *addr.AppAddr) {
h.mu.Lock()
defer h.mu.Unlock()
if !a.Equal(h.addr) {
h.addr = a.Copy()
h.failCount = 0
h.lastFail = time.Now()
h.lastExp = time.Now()
}
}
// Key returns the info key.
func (h *Info) Key() string {
return h.key
}
// Addr returns the address of the discovery service instance.
func (h *Info) Addr() *addr.AppAddr {
h.mu.Lock()
defer h.mu.Unlock()
return h.addr.Copy()
}
// FailCount returns the fail count.
func (h *Info) FailCount() int {
h.mu.Lock()
defer h.mu.Unlock()
h.expireFails(time.Now())
return int(h.failCount)
}
// Fail adds to the fail count.
func (h *Info) Fail() {
h.mu.Lock()
defer h.mu.Unlock()
h.expireFails(time.Now())
h.lastFail = time.Now()
if h.failCount < math.MaxInt16 {
h.failCount++
}
}
// expireFails reduces the fail count if the last fail is sufficiently long in the past.
// The caller is assumed to hold the lock on h.
func (h *Info) expireFails(now time.Time) {
if now.Sub(h.lastFail) > failExpStart && now.Sub(h.lastExp) > failExpInterval {
for i := 0; i < int(now.Sub(h.lastExp)/failExpInterval); i++ {
h.failCount /= 2
}
h.lastExp = now
}
}
func (h *Info) String() string {
h.mu.Lock()
defer h.mu.Unlock()
return fmt.Sprintf("Key: %s lastFail: %s failCount: %d", h.key, h.lastFail, h.failCount)
}