/
dalga.go
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/
dalga.go
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package dalga
import (
"database/sql"
"errors"
"flag"
"fmt"
"log"
"net"
"os"
"sync"
"time"
"github.com/cenkalti/dalga/dalga/Godeps/_workspace/src/github.com/fzzy/radix/redis"
)
const Version = "1.0.0"
var debugging = flag.Bool("debug", false, "turn on debug messages")
const (
redisLockKey = "dalga-lock"
redisLockExpiry = 30 * time.Second
redisLockRenewAfter = 20 * time.Second
)
func debug(args ...interface{}) {
if *debugging {
log.Println(args...)
}
}
type Dalga struct {
config Config
redis *redis.Client
db *sql.DB
listener net.Listener
Jobs *JobManager
scheduler *scheduler
// will be closed when dalga is ready to accept requests
ready chan struct{}
// will be closed by Shutdown method
shutdown chan struct{}
onceShutdown sync.Once
}
func New(config Config) (*Dalga, error) {
if config.Jobs.RandomizationFactor < 0 || config.Jobs.RandomizationFactor > 1 {
return nil, errors.New("randomization factor must be between 0 and 1")
}
db, err := sql.Open("mysql", config.MySQL.DSN())
if err != nil {
return nil, err
}
t := &table{db, config.MySQL.Table}
s := newScheduler(t, config.Endpoint.BaseURL, time.Duration(config.Endpoint.Timeout)*time.Second, config.Jobs.RandomizationFactor)
m := newJobManager(t, s)
return &Dalga{
config: config,
db: db,
Jobs: m,
scheduler: s,
ready: make(chan struct{}),
shutdown: make(chan struct{}),
}, nil
}
// Run Dalga. This function is blocking. Returns nil after Shutdown is called.
func (d *Dalga) Run() error {
var err error
d.listener, err = net.Listen("tcp", d.config.Listen.Addr())
if err != nil {
return err
}
log.Println("listening", d.listener.Addr())
if !d.config.Redis.Zero() {
hostname, err := os.Hostname()
if err != nil {
return err
}
value := fmt.Sprintf("%s:%d", hostname, d.listener.Addr().(*net.TCPAddr).Port)
d.redis, err = redis.Dial("tcp", d.config.Redis.Addr())
if err != nil {
return err
}
log.Print("connected to redis")
if err = d.acquireRedisLock(value); err != nil {
return err
}
defer d.redis.Cmd("DEL", redisLockKey) // release lock before exit
go d.renewRedisLock(value)
}
d.db, err = sql.Open("mysql", d.config.MySQL.DSN())
if err != nil {
return err
}
defer d.db.Close()
if err = d.db.Ping(); err != nil {
return err
}
log.Print("connected to mysql")
log.Print("dalga is ready")
close(d.ready)
go d.scheduler.Run()
defer func() {
d.scheduler.Stop()
<-d.scheduler.NotifyDone()
}()
if err = d.serveHTTP(); err != nil {
select {
case _, ok := <-d.shutdown:
if !ok {
// shutdown in progress, do not return error
return nil
}
default:
}
}
return err
}
func (d *Dalga) acquireRedisLock(value string) error {
log.Print("acquiring redis lock")
reply := d.redis.Cmd("SET", redisLockKey, value, "NX", "PX", int(redisLockExpiry/time.Millisecond))
if reply.Err != nil {
return reply.Err
}
status, _ := reply.Str()
if status != "OK" {
return errors.New("cannot acquire redis lock")
}
log.Print("acquired redis lock")
return nil
}
func (d *Dalga) renewRedisLock(value string) {
for {
select {
case <-time.After(redisLockRenewAfter):
debug("renewing redis lock")
reply := d.redis.Cmd("EVAL", `
if redis.call("GET", KEYS[1]) == ARGV[1] then
return redis.call("SET", KEYS[1], ARGV[1], "PX", ARGV[2])
else
return 0
end
`, 1, redisLockKey, value, int(redisLockExpiry/time.Millisecond))
if reply.Err != nil {
log.Print(reply.Err)
d.Shutdown()
return
}
status, _ := reply.Str()
if status != "OK" {
log.Print("cannot renew redis lock")
d.Shutdown()
return
}
debug("lock renewed")
case <-d.scheduler.NotifyDone():
return
}
}
}
// Shutdown running Dalga gracefully.
func (d *Dalga) Shutdown() {
d.onceShutdown.Do(func() {
close(d.shutdown)
if err := d.listener.Close(); err != nil {
log.Print(err)
}
})
}
// NotifyReady returns a channel that will be closed when Dalga is ready to accept HTTP requests.
func (d *Dalga) NotifyReady() <-chan struct{} {
return d.ready
}
// CreateTable creates the table for storing jobs on database.
func (d *Dalga) CreateTable() error {
db, err := sql.Open("mysql", d.config.MySQL.DSN())
if err != nil {
return err
}
defer db.Close()
t := &table{db, d.config.MySQL.Table}
return t.Create()
}