srv.go: peak handling

cmd/peakHandling.go

@@ -0,0 +1,79 @@
+package main
+
+import (
+	"log"
+	"net/http"
+	"sync"
+	"time"
+
+	"github.com/robfig/cron"
+)
+
+var peakRequest30 sync.Map
+var peakRequest60 sync.Map
+
+func initPeakHandling() {
+	c := cron.New()
+	// cronTime := fmt.Sprintf("%d,%d * * * *", 30-prefetchInterval/60, 60-prefetchInterval/60)
+	c.AddFunc("24 * * * *", prefetchPeakRequests30)
+	c.AddFunc("54 * * * *", prefetchPeakRequests60)
+	c.Start()
+}
+
+func savePeakRequest(cacheDigest string, r *http.Request) {
+	_, min, _ := time.Now().Clock()
+	if min == 30 {
+		peakRequest30.Store(cacheDigest, *r)
+	} else if min == 0 {
+		peakRequest60.Store(cacheDigest, *r)
+	}
+}
+
+func prefetchRequest(r *http.Request) {
+	processRequest(r)
+}
+
+func syncMapLen(sm *sync.Map) int {
+	count := 0
+
+	f := func(key, value interface{}) bool {
+
+		// Not really certain about this part, don't know for sure
+		// if this is a good check for an entry's existence
+		if key == "" {
+			return false
+		}
+		count++
+
+		return true
+	}
+
+	sm.Range(f)
+
+	return count
+}
+
+func prefetchPeakRequests(peakRequestMap *sync.Map) {
+	peakRequestLen := syncMapLen(peakRequestMap)
+	log.Printf("PREFETCH: Prefetching %d requests\n", peakRequestLen)
+	if peakRequestLen == 0 {
+		return
+	}
+	sleepBetweenRequests := time.Duration(prefetchInterval*1000/peakRequestLen) * time.Millisecond
+	peakRequestMap.Range(func(key interface{}, value interface{}) bool {
+		r := value.(http.Request)
+		log.Printf("Prefetching %s\n", key)
+		prefetchRequest(&r)
+		peakRequestMap.Delete(key)
+		time.Sleep(sleepBetweenRequests)
+		return true
+	})
+}
+
+func prefetchPeakRequests30() {
+	prefetchPeakRequests(&peakRequest30)
+}
+
+func prefetchPeakRequests60() {
+	prefetchPeakRequests(&peakRequest60)
+}

cmd/processRequest.go

@@ -0,0 +1,130 @@
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"log"
+	"math/rand"
+	"net"
+	"net/http"
+	"time"
+)
+
+func processRequest(r *http.Request) responseWithHeader {
+	var response responseWithHeader
+
+	foundInCache := false
+	cacheDigest := getCacheDigest(r)
+
+	savePeakRequest(cacheDigest, r)
+
+	cacheBody, ok := lruCache.Get(cacheDigest)
+	if ok {
+		cacheEntry := cacheBody.(responseWithHeader)
+
+		// if after all attempts we still have no answer,
+		// we try to make the query on our own
+		for attempts := 0; attempts < 300; attempts++ {
+			if !ok || !cacheEntry.InProgress {
+				break
+			}
+			time.Sleep(30 * time.Millisecond)
+			cacheBody, ok = lruCache.Get(cacheDigest)
+			cacheEntry = cacheBody.(responseWithHeader)
+		}
+		if cacheEntry.InProgress {
+			log.Printf("TIMEOUT: %s\n", cacheDigest)
+		}
+		if ok && !cacheEntry.InProgress && cacheEntry.Expires.After(time.Now()) {
+			response = cacheEntry
+			foundInCache = true
+		}
+	}
+
+	if !foundInCache {
+		lruCache.Add(cacheDigest, responseWithHeader{InProgress: true})
+		response = get(r)
+		if response.StatusCode == 200 || response.StatusCode == 304 {
+			lruCache.Add(cacheDigest, response)
+		} else {
+			log.Printf("REMOVE: %d response for %s from cache\n", response.StatusCode, cacheDigest)
+			lruCache.Remove(cacheDigest)
+		}
+	}
+	return response
+}
+
+func get(req *http.Request) responseWithHeader {
+
+	client := &http.Client{}
+
+	queryURL := fmt.Sprintf("http://%s%s", req.Host, req.RequestURI)
+
+	proxyReq, err := http.NewRequest(req.Method, queryURL, req.Body)
+	if err != nil {
+		log.Printf("Request: %s\n", err)
+	}
+
+	// proxyReq.Header.Set("Host", req.Host)
+	// proxyReq.Header.Set("X-Forwarded-For", req.RemoteAddr)
+
+	for header, values := range req.Header {
+		for _, value := range values {
+			proxyReq.Header.Add(header, value)
+		}
+	}
+
+	res, err := client.Do(proxyReq)
+
+	if err != nil {
+		panic(err)
+	}
+
+	body, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		log.Println(err)
+	}
+
+	return responseWithHeader{
+		InProgress: false,
+		Expires:    time.Now().Add(time.Duration(randInt(1000, 1500)) * time.Second),
+		Body:       body,
+		Header:     res.Header,
+		StatusCode: res.StatusCode,
+	}
+}
+
+// implementation of the cache.get_signature of original wttr.in
+func getCacheDigest(req *http.Request) string {
+
+	userAgent := req.Header.Get("User-Agent")
+
+	queryHost := req.Host
+	queryString := req.RequestURI
+
+	clientIPAddress := readUserIP(req)
+
+	lang := req.Header.Get("Accept-Language")
+
+	return fmt.Sprintf("%s:%s%s:%s:%s", userAgent, queryHost, queryString, clientIPAddress, lang)
+}
+
+func readUserIP(r *http.Request) string {
+	IPAddress := r.Header.Get("X-Real-Ip")
+	if IPAddress == "" {
+		IPAddress = r.Header.Get("X-Forwarded-For")
+	}
+	if IPAddress == "" {
+		IPAddress = r.RemoteAddr
+		var err error
+		IPAddress, _, err = net.SplitHostPort(IPAddress)
+		if err != nil {
+			log.Printf("ERROR: userip: %q is not IP:port\n", IPAddress)
+		}
+	}
+	return IPAddress
+}
+
+func randInt(min int, max int) int {
+	return min + rand.Intn(max-min)
+}

cmd/srv.go

@@ -2,113 +2,48 @@ package main
 
 import (
 	"context"
-	"fmt"
-	"io/ioutil"
 	"log"
 	"net"
 	"net/http"
 	"time"
 
-	"github.com/hashicorp/golang-lru"
+	lru "github.com/hashicorp/golang-lru"
 )
 
+const uplinkSrvAddr = "127.0.0.1:9002"
+const uplinkTimeout = 30
+const prefetchInterval = 300
+const lruCacheSize = 12800
+
 var lruCache *lru.Cache
 
-type ResponseWithHeader struct {
+type responseWithHeader struct {
+	InProgress bool      // true if the request is being processed
+	Expires    time.Time // expiration time of the cache entry
+
 	Body       []byte
 	Header     http.Header
 	StatusCode int // e.g. 200
-
 }
 
 func init() {
 	var err error
-	lruCache, err = lru.New(12800)
+	lruCache, err = lru.New(lruCacheSize)
 	if err != nil {
 		panic(err)
 	}
 
 	dialer := &net.Dialer{
-		Timeout:   30 * time.Second,
+		Timeout:   uplinkTimeout * time.Second,
-		KeepAlive: 30 * time.Second,
+		KeepAlive: uplinkTimeout * time.Second,
 		DualStack: true,
 	}
 
-	http.DefaultTransport.(*http.Transport).DialContext = func(ctx context.Context, network, addr string) (net.Conn, error) {
+	http.DefaultTransport.(*http.Transport).DialContext = func(ctx context.Context, network, _ string) (net.Conn, error) {
-		addr = "127.0.0.1:8002"
+		return dialer.DialContext(ctx, network, uplinkSrvAddr)
-		return dialer.DialContext(ctx, network, addr)
-	}
-
-}
-
-func readUserIP(r *http.Request) string {
-	IPAddress := r.Header.Get("X-Real-Ip")
-	if IPAddress == "" {
-		IPAddress = r.Header.Get("X-Forwarded-For")
-	}
-	if IPAddress == "" {
-		IPAddress = r.RemoteAddr
-		var err error
-		IPAddress, _, err = net.SplitHostPort(IPAddress)
-		if err != nil {
-			fmt.Printf("userip: %q is not IP:port\n", IPAddress)
-		}
-	}
-	return IPAddress
-}
-
-// implementation of the cache.get_signature of original wttr.in
-func findCacheDigest(req *http.Request) string {
-
-	userAgent := req.Header.Get("User-Agent")
-
-	queryHost := req.Host
-	queryString := req.RequestURI
-
-	clientIpAddress := readUserIP(req)
-
-	lang := req.Header.Get("Accept-Language")
-
-	now := time.Now()
-	secs := now.Unix()
-	timestamp := secs / 1000
-
-	return fmt.Sprintf("%s:%s%s:%s:%s:%d", userAgent, queryHost, queryString, clientIpAddress, lang, timestamp)
-}
-
-func get(req *http.Request) ResponseWithHeader {
-
-	client := &http.Client{}
-
-	queryURL := fmt.Sprintf("http://%s%s", req.Host, req.RequestURI)
-
-	proxyReq, err := http.NewRequest(req.Method, queryURL, req.Body)
-	if err != nil {
-		// handle error
-	}
-
-	// proxyReq.Header.Set("Host", req.Host)
-	// proxyReq.Header.Set("X-Forwarded-For", req.RemoteAddr)
-
-	for header, values := range req.Header {
-		for _, value := range values {
-			proxyReq.Header.Add(header, value)
-		}
 	}
 
-	res, err := client.Do(proxyReq)
+	initPeakHandling()
-
-	if err != nil {
-		panic(err)
-	}
-
-	body, err := ioutil.ReadAll(res.Body)
-
-	return ResponseWithHeader{
-		Body:       body,
-		Header:     res.Header,
-		StatusCode: res.StatusCode,
-	}
 }
 
 func copyHeader(dst, src http.Header) {
@@ -120,26 +55,14 @@ func copyHeader(dst, src http.Header) {
 }
 
 func main() {
-
 	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
-		var response ResponseWithHeader
+		// printStat()
+		response := processRequest(r)
 
-		cacheDigest := findCacheDigest(r)
-		cacheBody, ok := lruCache.Get(cacheDigest)
-		if ok {
-			response = cacheBody.(ResponseWithHeader)
-		} else {
-			fmt.Println(cacheDigest)
-			response = get(r)
-			if response.StatusCode == 200 {
-				lruCache.Add(cacheDigest, response)
-			}
-		}
 		copyHeader(w.Header(), response.Header)
 		w.WriteHeader(response.StatusCode)
 		w.Write(response.Body)
 	})
 
-	log.Fatal(http.ListenAndServe(":8081", nil))
+	log.Fatal(http.ListenAndServe(":8082", nil))
-
 }

cmd/stat.go

@@ -0,0 +1,40 @@
+package main
+
+import (
+	"log"
+	"sync"
+	"time"
+)
+
+type safeCounter struct {
+	v   map[int]int
+	mux sync.Mutex
+}
+
+func (c *safeCounter) inc(key int) {
+	c.mux.Lock()
+	c.v[key]++
+	c.mux.Unlock()
+}
+
+// func (c *safeCounter) val(key int) int {
+// 	c.mux.Lock()
+// 	defer c.mux.Unlock()
+// 	return c.v[key]
+// }
+//
+// func (c *safeCounter) reset(key int) int {
+// 	c.mux.Lock()
+// 	defer c.mux.Unlock()
+// 	result := c.v[key]
+// 	c.v[key] = 0
+// 	return result
+// }
+
+var queriesPerMinute safeCounter
+
+func printStat() {
+	_, min, _ := time.Now().Clock()
+	queriesPerMinute.inc(min)
+	log.Printf("Processed %d requests\n", min)
+}