server/jobscheduler/jobscheduler.go

package jobscheduler

import (
	"context"
	"time"

	"git.ohea.xyz/cursorius/server/config"
	"github.com/op/go-logging"
	"nhooyr.io/websocket"
	"nhooyr.io/websocket/wsjson"
)

var log = logging.MustGetLogger("cursorius-server")

type RunnerRegistration struct {
	Secret string
	Id     string
	Tags   []string
	conn   *websocket.Conn
}

type RunnerData struct {
	msgType websocket.MessageType
	data    []byte
}

type Runner struct {
	id          string
	tags        []string
	conn        *websocket.Conn
	receiveChan chan RunnerData
	running     bool
}

type jobScheduler struct {
	runCh             chan Run
	registerCh        chan RunnerRegistration
	connectedRunners  []Runner
	configuredRunners map[string]config.Runner
}

type Run struct {
	JobName   string
	JobConfig config.Job
	Ref       string
}

type runnerJob struct {
	Id  string
	URL string
}

func runJobScheduler(j jobScheduler) {
	for {
		select {
		case run := <-j.runCh:
			log.Infof("Launching run for job \"%v\" on ref \"%v\"", run.JobName, run.Ref)
			log.Debugf("Finding runner for job \"%v\"", run.JobName)
			rJ := runnerJob{
				Id:  run.JobName,
				URL: run.JobConfig.URL,
			}
			launched := false
			for i, runner := range j.connectedRunners {
				// don't send job to runner that is already occupied
				if !runner.running {
					// don't send job to runner with closed receiveChan (is defunct)
					// there should never be messages to read on an inactive runner,
					// so we aren't losing any data here
					select {
					case <-runner.receiveChan:
						// if the receive channel is closed, swap delete the runner as it's defunct
						j.connectedRunners[i] = j.connectedRunners[len(j.connectedRunners)-1]
						j.connectedRunners = j.connectedRunners[:len(j.connectedRunners)-1]
					default:
						err := wsjson.Write(context.Background(), runner.conn, rJ)
						if err != nil {
							log.Errorf("Could not launch run: %v", err)
							break
						} else {
							log.Infof("Launched run for job %v on runner %v", run.JobName, runner.id)
							launched = true
							j.connectedRunners[i].running = true
							break
						}
					}
				} else {
					log.Debugf("Skipping runner %v, as runner is activly running another job", runner.id)
				}
			}
			if !launched {
				errorMsg := "could not find valid runner"
				if len(j.connectedRunners) == 0 {
					errorMsg = "no connected runners"
				}
				log.Errorf("Could not launch run for job \"%v\": %v", run.JobName, errorMsg)
			}
		case registration := <-j.registerCh:
			log.Debugf("New runner appeared with id: %v and secret: %v", registration.Id, registration.Secret)
			if configuredRunner, doesExist := j.configuredRunners[registration.Id]; doesExist {
				if configuredRunner.Secret == registration.Secret {
					log.Infof("Registering runner \"%v\" with tags %v", registration.Id, registration.Tags)
					runner := Runner{
						id:          registration.Id,
						tags:        registration.Tags,
						conn:        registration.conn,
						receiveChan: make(chan RunnerData),
						running:     false,
					}
					j.connectedRunners = append(j.connectedRunners, runner)
					// start goroutine to call Read function on websocket connection
					// this is required to keep the connection functioning
					go func() {
						for {
							msgType, data, err := registration.conn.Read(context.Background())
							if err != nil {
								// TODO: this is still racy, since a job could be emitted between the
								// connection returning an err and the channel closing
								close(runner.receiveChan)
								log.Errorf("Could not read from connection: %v", err)
								log.Noticef("Deregistering runner with id: %v", runner.id)

								return
							} else {
								log.Debugf("%v: %v", msgType, data)
								runner.receiveChan <- RunnerData{msgType: msgType, data: data}
							}
						}
					}()

				} else {
					log.Errorf("Disconnecting runner with id: %v and invalid secret: %v", registration.Id, registration.Secret)
					registration.conn.Close(websocket.StatusNormalClosure, "registration invalid")
				}
			} else {
				log.Errorf("Disconnecting runner with invalid id: %v", registration.Id)
				registration.conn.Close(websocket.StatusNormalClosure, "registration invalid")
			}
		}
	}
}

func StartJobScheduler(jobs map[string]config.Job, configuredRunners map[string]config.Runner) (chan Run, chan RunnerRegistration, error) {
	scheduler := jobScheduler{
		runCh:             make(chan Run),
		registerCh:        make(chan RunnerRegistration),
		connectedRunners:  make([]Runner, 0),
		configuredRunners: configuredRunners,
	}

	go runJobScheduler(scheduler)

	return scheduler.runCh, scheduler.registerCh, nil
}

func RegisterRunner(conn *websocket.Conn, registerCh chan RunnerRegistration) {
	ctx, cancel := context.WithTimeout(context.Background(), time.Second*10)
	defer cancel()

	var registration RunnerRegistration
	registration.conn = conn
	err := wsjson.Read(ctx, conn, &registration)
	if err != nil {
		log.Errorf("Could not read data from websocket connection: %v", err)
		return
	}
	registerCh <- registration
}