implemented queuing update requests and canceling new ones when the queue is full

Makefile

@@ -56,7 +56,7 @@ run-testserver:
 	bin/testserver -json-file var/cse-globus-stage-b-with-main-section.json
 
 run-contentserver:
-	contentserver -var-dir var -webserver-address :9191 -address :9999 -log-level debug http://127.0.0.1:1234
+	contentserver -var-dir var -webserver-address :9191 -address :9999 -log-level notice http://127.0.0.1:1234
 
 clean-var:
 	rm var/contentserver-repo-2019*

repo/loader.go

@@ -17,14 +17,15 @@ var json = jsoniter.ConfigCompatibleWithStandardLibrary
 func (repo *Repo) updateRoutine() {
 	go func() {
 		for newDimension := range repo.updateChannel {
-			log.Debug("update routine received a new dimension: " + newDimension.Dimension)
+			log.Notice("update routine received a new dimension: " + newDimension.Dimension)
 
 			err := repo._updateDimension(newDimension.Dimension, newDimension.Node)
-			log.Debug("update routine received result")
+			log.Notice("update routine received result")
 			if err != nil {
 				log.Debug("	update routine error: " + err.Error())
 			}
 			repo.updateDoneChannel <- err
+			repo.updateCompleteChannel <- true
 		}
 	}()
 }
@@ -110,11 +111,19 @@ func loadNodesFromJSON(jsonBytes []byte) (nodes map[string]*content.RepoNode, er
 }
 
 func (repo *Repo) tryToRestoreCurrent() error {
-	currentJSONBytes, err := repo.history.getCurrent()
-	if err != nil {
-		return err
+
+	select {
+	case repo.updateInProgressChannel <- time.Now():
+		log.Notice("update request added to queue")
+		currentJSONBytes, err := repo.history.getCurrent()
+		if err != nil {
+			return err
+		}
+		return repo.loadJSONBytes(currentJSONBytes)
+	default:
+		log.Notice("invalidation request ignored, queue seems to be full")
+		return errors.New("queue full")
 	}
-	return repo.loadJSONBytes(currentJSONBytes)
 }
 
 func get(URL string) (data []byte, err error) {
@@ -130,11 +139,6 @@ func get(URL string) (data []byte, err error) {
 }
 
 func (repo *Repo) update() (repoRuntime int64, jsonBytes []byte, err error) {
-
-	// limit ressources and allow only one update request at once
-	repo.updateLock.Lock()
-	defer repo.updateLock.Unlock()
-
 	startTimeRepo := time.Now().UnixNano()
 	jsonBytes, err = get(repo.server)
 	repoRuntime = time.Now().UnixNano() - startTimeRepo
@@ -157,6 +161,18 @@ func (repo *Repo) update() (repoRuntime int64, jsonBytes []byte, err error) {
 	return repoRuntime, jsonBytes, nil
 }
 
+// limit ressources and allow only one update request at once
+func (repo *Repo) tryUpdate() (repoRuntime int64, jsonBytes []byte, err error) {
+	select {
+	case repo.updateInProgressChannel <- time.Now():
+		log.Notice("update request added to queue")
+		return repo.update()
+	default:
+		log.Notice("invalidation request ignored, queue seems to be full")
+		return 0, nil, errors.New("queue full")
+	}
+}
+
 func (repo *Repo) loadJSONBytes(jsonBytes []byte) error {
 	nodes, err := loadNodesFromJSON(jsonBytes)
 	if err != nil {

repo/repo.go

@@ -4,7 +4,6 @@ import (
 	"errors"
 	"fmt"
 	"strings"
-	"sync"
 	"time"
 
 	"github.com/foomo/contentserver/content"
@@ -24,12 +23,14 @@ type Dimension struct {
 
 // Repo content repositiory
 type Repo struct {
-	server            string
-	Directory         map[string]*Dimension
-	updateLock        *sync.Mutex
-	updateChannel     chan *repoDimension
-	updateDoneChannel chan error
-	history           *history
+	server    string
+	Directory map[string]*Dimension
+	// updateLock        sync.Mutex
+	updateChannel           chan *repoDimension
+	updateDoneChannel       chan error
+	history                 *history
+	updateInProgressChannel chan time.Time
+	updateCompleteChannel   chan bool
 }
 
 type repoDimension struct {
@@ -42,15 +43,26 @@ func NewRepo(server string, varDir string) *Repo {
 	log.Notice("creating new repo for " + server)
 	log.Notice("	using var dir:" + varDir)
 	repo := &Repo{
-		server:            server,
-		Directory:         map[string]*Dimension{},
-		history:           newHistory(varDir),
-		updateLock:        &sync.Mutex{},
-		updateChannel:     make(chan *repoDimension),
-		updateDoneChannel: make(chan error),
+		server:                  server,
+		Directory:               map[string]*Dimension{},
+		history:                 newHistory(varDir),
+		updateChannel:           make(chan *repoDimension),
+		updateDoneChannel:       make(chan error),
+		updateInProgressChannel: make(chan time.Time, 1),
+		updateCompleteChannel:   make(chan bool),
 	}
+	go func() {
+		for {
+			select {
+			case t := <-repo.updateInProgressChannel:
+				log.Notice("got timestamp: ", t, "waiting for update to complete")
+				<-repo.updateCompleteChannel
+				log.Notice("update completed!")
+			}
+		}
+	}()
 	go repo.updateRoutine()
-	log.Record("trying to restore pervious state")
+	log.Record("trying to restore previous state")
 	restoreErr := repo.tryToRestoreCurrent()
 	if restoreErr != nil {
 		log.Record("	could not restore previous repo content:" + restoreErr.Error())
@@ -194,10 +206,12 @@ func (repo *Repo) Update() (updateResponse *responses.Update) {
 		return float64(float64(nanoSeconds) / float64(1000000000.0))
 	}
 	startTime := time.Now().UnixNano()
-	updateRepotime, jsonBytes, updateErr := repo.update()
+	updateRepotime, jsonBytes, updateErr := repo.tryUpdate()
 	updateResponse = &responses.Update{}
 	updateResponse.Stats.RepoRuntime = floatSeconds(updateRepotime)
 
+	log.Notice("Update triggered")
+
 	if updateErr != nil {
 		updateResponse.Success = false
 		updateResponse.Stats.NumberOfNodes = -1

server/server.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"net"
 	"net/http"
+	"os"
 
 	"github.com/foomo/contentserver/log"
 	"github.com/foomo/contentserver/repo"
@@ -40,23 +41,35 @@ func Run(server string, address string, varDir string) error {
 func RunServerSocketAndWebServer(
 	server string,
 	address string,
-	webserverAdresss string,
+	webserverAddress string,
 	webserverPath string,
 	varDir string,
 ) error {
-	if address == "" && webserverAdresss == "" {
+	if address == "" && webserverAddress == "" {
 		return errors.New("one of the addresses needs to be set")
 	}
 	log.Record("building repo with content from " + server)
 	r := repo.NewRepo(server, varDir)
-	go r.Update()
+
+	// start initial update and handle error
+	go func() {
+		resp := r.Update()
+		if !resp.Success {
+			log.Error("failed to update: ", resp)
+			os.Exit(1)
+		}
+	}()
+
 	// update can run in bg
 	chanErr := make(chan error)
+
 	if address != "" {
+		log.Notice("starting socketserver on: ", address)
 		go runSocketServer(r, address, chanErr)
 	}
-	if webserverAdresss != "" {
-		go runWebserver(r, webserverAdresss, webserverPath, chanErr)
+	if webserverAddress != "" {
+		log.Notice("starting webserver on: ", webserverAddress)
+		go runWebserver(r, webserverAddress, webserverPath, chanErr)
 	}
 	return <-chanErr
 }

testing/client/client.go

@@ -25,7 +25,7 @@ func main() {
 			}
 			log.Println(num, "update done", resp)
 		}(i)
-		time.Sleep(5 * time.Second)
+		time.Sleep(1 * time.Second)
 	}
 
 	log.Println("done")