Futurama

Futurama is a mysql backed priority queue for scheduling delayed events, written in Go.

• It allows you to execute events at specified time in future.
• Different from background batch job targeted job queues, it is good at handling simple/small tasks (e.g. calling a http API after 30sec) under heavy production load.
• It has a stateless design so that you can run multiple instances for load balancing or failover.
• It is empowering one of top ranked MMO strategy game - War of Nations.
• It is supposed to support multiple backends for storing events, for the time being only MySQL is officially implemented.

Requirements

Well tested with:

• Go >= 1.3
• MySQL >= 5.5

Basic usage

// create a queue
q := futurama.CreateQueue(config, map[string]TriggerInterface{
      triggerType: trigger,
      ...
})
q.Start()

// schedule an event
triggerTime := time.Now().Add(3 * time.Second)
evId := q.Create(triggerType, triggerTime, triggerParam)

// cancel the event
if we_want_to_cancel {
  q.Cancel(evId)
}

// stop the queue
q.Stop()

• Create an event queue with futurama.CreateQueue.
  • 1st arg config provides access to MySQL .. etc.
  • 2nd arg provides triggers with a map of string -> TriggerInterface, these triggers are used to process events.
• Calling q.Create() with triggerType(string), triggerTime(time.Time) and triggerParams(interface{}) will add an event to queue.
  • Later at triggerTime, a trigger associated with triggerType will be called.
• q.Create() returns the id(string) of created event, id can be use for cancelling the event.

Config

By default, futurama connects to local MySQL server (host=127.0.0.1, port=3306). You can either create a default config and replace with customized values:

config := futurama.DefaultConfig()
config.Host = "example.com"
config.User = "dev"
config.Pass = "..."

q := futurama.CreateQueue(config, triggers)
...

or load config values from a json file - a Config object is json deserializable:

configFile := "queue.json"
config := futurama.DefaultConfig()
file, _ := ioutil.ReadFile(configFile)
json.Unmarshal(file, config)

q := futurama.CreateQueue(config, triggers)
...

inside queue.json:

{
  "mysql6": false,
  "username": "dev",
  "password": "...",
  "host": "example.com"
} // see config.go for more setting options 

NOTE: By enabling mysql6, scheduled time can be specified in millisecond (and futurama needs to actually connect to a MySQL server that supports DATETIME(6))

Triggers

A trigger can be any go struct that implements TriggerInterface (see interface.go)

type TriggerResult struct {
	Status      EventStatus
	TriggerTime time.Time
	Data        interface{}
}

type TriggerInterface interface {
 Trigger(ev *Event) *TriggerResult
}

• ev *Event is created by q.Create(triggerType, triggerTime, triggerParam)
• Trigger function is called at triggerTime, it can access triggerParam through ev.Data

Retry on failures(Backoff)

• Events will be re-scheduled if Trigger function failed (return ``TriggerResult.Status = EventStatus_RETRY```)
• Re-scheduled triggerTime is delayed upon failures by following exponential backoff
• Max number of re-attempts is 18 by default, it can be configured by Config.SchedulerConfig.MaxRetry, after MaxRetry, the event will be forgotten (removed from DB) ...

Running test

go test -v -logtostderr