Distribute load between three backend servers

internal/config/config.go

@@ -50,8 +50,17 @@ type Server struct {
 
 // Uplink configuration.
 type Uplink struct {
-	// Address contains address of the uplink server in form IP:PORT.
-	Address string `yaml:"address,omitempty"`
+	// Address1 contains address of the uplink server in form IP:PORT
+	// for format=j1 queries.
+	Address1 string `yaml:"address1,omitempty"`
+
+	// Address2 contains address of the uplink server in form IP:PORT
+	// for format=* queries.
+	Address2 string `yaml:"address2,omitempty"`
+
+	// Address3 contains address of the uplink server in form IP:PORT
+	// for all other queries.
+	Address3 string `yaml:"address3,omitempty"`
 
 	// Timeout for upstream queries.
 	Timeout int `yaml:"timeout,omitempty"`
@@ -85,7 +94,7 @@ type Geo struct {
 
 	LocationCacheType types.CacheType `yaml:"locationCacheType,omitempty"`
 
-	Nominatim []Nominatim
+	Nominatim []Nominatim `yaml:"nominatim"`
 }
 
 type Nominatim struct {
@@ -140,7 +149,9 @@ func Default() *Config {
 			TLSKeyFile:  "/wttr.in/etc/privkey.pem",
 		},
 		Uplink{
-			Address:          "127.0.0.1:9002",
+			Address1:         "127.0.0.1:9002",
+			Address2:         "127.0.0.1:9002",
+			Address3:         "127.0.0.1:9002",
 			Timeout:          30,
 			PrefetchInterval: 300,
 		},

internal/geo/ip/ip.go

@@ -10,12 +10,13 @@ import (
 	"strconv"
 	"strings"
 
+	"github.com/samonzeweb/godb"
+	"github.com/samonzeweb/godb/adapters/sqlite"
+
 	"github.com/chubin/wttr.in/internal/config"
 	"github.com/chubin/wttr.in/internal/routing"
 	"github.com/chubin/wttr.in/internal/types"
 	"github.com/chubin/wttr.in/internal/util"
-	"github.com/samonzeweb/godb"
-	"github.com/samonzeweb/godb/adapters/sqlite"
 )
 
 // Address information.

internal/processor/processor.go

@@ -3,7 +3,6 @@ package processor
 import (
 	"context"
 	"fmt"
-	"io/ioutil"
 	"log"
 	"math/rand"
 	"net"
@@ -52,15 +51,17 @@ type ResponseWithHeader struct {
 
 // RequestProcessor handles incoming requests.
 type RequestProcessor struct {
-	peakRequest30     sync.Map
-	peakRequest60     sync.Map
-	lruCache          *lru.Cache
-	stats             *stats.Stats
-	router            routing.Router
-	upstreamTransport *http.Transport
-	config            *config.Config
-	geoIPCache        *geoip.Cache
-	geoLocation       *geoloc.Cache
+	peakRequest30      sync.Map
+	peakRequest60      sync.Map
+	lruCache           *lru.Cache
+	stats              *stats.Stats
+	router             routing.Router
+	upstreamTransport1 *http.Transport
+	upstreamTransport2 *http.Transport
+	upstreamTransport3 *http.Transport
+	config             *config.Config
+	geoIPCache         *geoip.Cache
+	geoLocation        *geoloc.Cache
 }
 
 // NewRequestProcessor returns new RequestProcessor.
@@ -76,9 +77,19 @@ func NewRequestProcessor(config *config.Config) (*RequestProcessor, error) {
 		DualStack: true,
 	}
 
-	transport := &http.Transport{
+	transport1 := &http.Transport{
 		DialContext: func(ctx context.Context, network, _ string) (net.Conn, error) {
-			return dialer.DialContext(ctx, network, config.Uplink.Address)
+			return dialer.DialContext(ctx, network, config.Uplink.Address1)
+		},
+	}
+	transport2 := &http.Transport{
+		DialContext: func(ctx context.Context, network, _ string) (net.Conn, error) {
+			return dialer.DialContext(ctx, network, config.Uplink.Address2)
+		},
+	}
+	transport3 := &http.Transport{
+		DialContext: func(ctx context.Context, network, _ string) (net.Conn, error) {
+			return dialer.DialContext(ctx, network, config.Uplink.Address3)
 		},
 	}
 
@@ -93,12 +104,14 @@ func NewRequestProcessor(config *config.Config) (*RequestProcessor, error) {
 	}
 
 	rp := &RequestProcessor{
-		lruCache:          lruCache,
-		stats:             stats.New(),
-		upstreamTransport: transport,
-		config:            config,
-		geoIPCache:        geoCache,
-		geoLocation:       geoLocation,
+		lruCache:           lruCache,
+		stats:              stats.New(),
+		upstreamTransport1: transport1,
+		upstreamTransport2: transport2,
+		upstreamTransport3: transport3,
+		config:             config,
+		geoIPCache:         geoCache,
+		geoLocation:        geoLocation,
 	}
 
 	// Initialize routes.
@@ -142,7 +155,7 @@ func (rp *RequestProcessor) ProcessRequest(r *http.Request) (*ResponseWithHeader
 	if dontCache(r) {
 		rp.stats.Inc("uncached")
 
-		return get(r, rp.upstreamTransport)
+		return getAny(r, rp.upstreamTransport1, rp.upstreamTransport2, rp.upstreamTransport3)
 	}
 
 	// processing cached request
@@ -173,8 +186,9 @@ func (rp *RequestProcessor) processRequestFromCache(r *http.Request) *ResponseWi
 		return nil
 	}
 
-	// if after all attempts we still have no answer,
-	// we try to make the query on our own
+	// If after all attempts we still have no answer,
+	// respond with an error message.
+	// (WAS: we try to make the query on our own)
 	for attempts := 0; attempts < 300; attempts++ {
 		if !ok || !cacheEntry.InProgress {
 			break
@@ -223,10 +237,7 @@ func (rp *RequestProcessor) processUncachedRequest(r *http.Request) (*ResponseWi
 		rp.stats.Inc("geoip")
 	}
 
-	// Indicate, that the request is being handled.
-	rp.lruCache.Add(cacheDigest, ResponseWithHeader{InProgress: true})
-
-	response, err = get(r, rp.upstreamTransport)
+	response, err = getAny(r, rp.upstreamTransport1, rp.upstreamTransport2, rp.upstreamTransport3)
 	if err != nil {
 		return nil, err
 	}