server/runnermanager/runnermanager.go

package runnermanager

import (
	"context"
	"fmt"
	"strings"
	"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 runnerManager struct {
	getRunnerCh       chan GetRunnerRequest
	registerCh        chan RunnerRegistration
	connectedRunners  []Runner
	configuredRunners map[string]config.Runner
}

type GetRunnerRequest struct {
	Tags     []string
	RespChan chan GetRunnerResponse
}

type GetRunnerResponse struct {
	Runner Runner
	Err    error
}

type runnerJob struct {
	Id  string
	URL string
}

func runRunnerManager(r runnerManager) {
	for {
	msgCase:
		select {
		case request := <-r.getRunnerCh:

			var runnerTagsStr strings.Builder
			fmt.Fprintf(&runnerTagsStr, "%v", request.Tags[0])
			for _, tag := range request.Tags[1:] {
				fmt.Fprintf(&runnerTagsStr, " %v", tag)
			}
			log.Infof("Got request for runner with tags \"%v\"", runnerTagsStr.String())

			log.Debugf("Finding runner with tags %v", runnerTagsStr)

			for i, runner := range r.connectedRunners {
				// don't allocate runner that is already occupied
				if runner.running {
					log.Debugf("Skipping runner %v, as runner is activly running another job", runner.id)
					continue
				}
				// don't allocate 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 _, ok := <-runner.receiveChan:
					if ok {
						// this should never happen
						log.Errorf("Recieved data from inactive runner %v, this is a bug", runner.id)
						continue
					}
					log.Noticef("Removing defunct runner \"%v\"", runner.id)
					// if the receive channel is closed, swap delete the runner as it's defunct
					r.connectedRunners[i] = r.connectedRunners[len(r.connectedRunners)-1]
					r.connectedRunners = r.connectedRunners[:len(r.connectedRunners)-1]
				default:
					runner.running = true
					request.RespChan <- GetRunnerResponse{
						Runner: runner,
						Err:    nil,
					}
					break msgCase
				}
			}
			errorMsg := "could not find valid runner"
			if len(r.connectedRunners) == 0 {
				errorMsg = "no connected runners"
			}
			log.Errorf("Could not allocate runner with tags \"%v\": %v", runnerTagsStr.String(), errorMsg)
			request.RespChan <- GetRunnerResponse{
				Runner: Runner{},
				Err:    fmt.Errorf("Could not allocate runner: %v", errorMsg),
			}

		case registration := <-r.registerCh:
			log.Debugf("New runner appeared with id: %v and secret: %v", registration.Id, registration.Secret)
			if configuredRunner, doesExist := r.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,
					}
					r.connectedRunners = append(r.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 runner could be alloctade 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 StartRunnerManager(configuredRunners map[string]config.Runner) (chan GetRunnerRequest, chan RunnerRegistration, error) {
	scheduler := runnerManager{
		getRunnerCh:       make(chan GetRunnerRequest),
		registerCh:        make(chan RunnerRegistration),
		connectedRunners:  make([]Runner, 0),
		configuredRunners: configuredRunners,
	}

	go runRunnerManager(scheduler)

	return scheduler.getRunnerCh, 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
}