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counter.go
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counter.go
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package sereno
import (
"strconv"
"time"
etcdc "github.com/coreos/etcd/client"
"golang.org/x/net/context"
)
func NewCounter(ctx context.Context, cid string, kapi etcdc.KeysAPI) (*DistributedCounter, error) {
keyid := "sereno/d/counter/" + cid
return NewDistributedCounter(ctx, keyid, DefaultTTL, kapi)
}
func NewDistributedCounter(ctx context.Context, keyid string, ttl time.Duration, kapi etcdc.KeysAPI) (*DistributedCounter, error) {
_, err := kapi.Get(ctx, keyid, nil)
if IsKeyNotFound(err) {
_, err := kapi.Create(ctx, keyid, "0")
if err != nil && !IsCompareAndSwapFailure(err) && !IsNodeExists(err) {
return nil, err
}
} else if err != nil {
return nil, err
}
keepalive, err := NewNodeKeepAlive(keyid, ttl, kapi)
if err != nil {
return nil, err
}
dlog("new counter:%v ttl:%v", keyid, ttl)
return &DistributedCounter{
ctx: ctx,
keyid: keyid,
kapi: kapi,
ttl: ttl,
stop: make(chan bool),
keepalive: keepalive,
}, nil
}
type DistributedCounter struct {
keyid string
kapi etcdc.KeysAPI
ttl time.Duration
ctx context.Context
keepalive *NodeKeepAlive
stop chan bool
}
func (c *DistributedCounter) Set(val int) error {
dlog("set:%v val:%v", c.keyid, val)
opts := &etcdc.SetOptions{TTL: c.ttl}
_, err := c.kapi.Set(c.ctx, c.keyid, strconv.Itoa(val), opts)
return err
}
func (c *DistributedCounter) Inc(n int) error {
const tries = 256
dlog("inc:%v val:%v", c.keyid, n)
evaluator := func(res *etcdc.Response, setOpts *etcdc.SetOptions) (val string, err error) {
valstr := res.Node.Value
i, err := strconv.Atoi(valstr)
if err != nil {
return "", err
}
n := i + n
setOpts.TTL = c.ttl // update the ttl also
setOpts.PrevValue = res.Node.Value
return strconv.Itoa(n), nil
}
return compareAndSwapUntil(context.Background(), tries, c.keyid, c.kapi, evaluator)
}
func (c *DistributedCounter) Dec(n int) error {
const tries = 256
dlog("dec:%v val:%v", c.keyid, n)
evaluator := func(res *etcdc.Response, setOpts *etcdc.SetOptions) (val string, err error) {
valstr := res.Node.Value
i, err := strconv.Atoi(valstr)
if err != nil {
return "", err
}
n := i - n
setOpts.TTL = c.ttl // update the ttl also
setOpts.PrevValue = res.Node.Value
return strconv.Itoa(n), nil
}
return compareAndSwapUntil(context.Background(), tries, c.keyid, c.kapi, evaluator)
}
func (c *DistributedCounter) Val() (int, error) {
k := c.kapi
resp, err := k.Get(c.ctx, c.keyid, &etcdc.GetOptions{Quorum: true})
if err != nil {
return 0, err
}
valstr := resp.Node.Value
return strconv.Atoi(valstr)
}
type CounterUpdate struct {
Cnt int
Err error
}
func (c *DistributedCounter) UnWatch() {
close(c.stop)
}