add --sort-endpoints-by command-line option

Add a few more options on how to sort endpoints of a backend. Currently
`--sort-backends` switches between the same k8s endpoints order and
naming order - which only makes sense if `backend-server-naming` was
changed.

`--sort-endpoints-by` also brings back the old behavior (v0.7 and older)
of missing `--sort-backends`: `random` option will shuffle endpoints of
all backends whenever a haproxy reload is fired.

docs/content/en/docs/configuration/command-line.md

@@ -36,6 +36,7 @@ The following command-line options are supported:
 | [`--rate-limit-update`](#rate-limit-update)             | uploads per second (float) | `0.5`                   |       |
 | [`--reload-strategy`](#reload-strategy)                 | [native\|reusesocket]      | `reusesocket`           |       |
 | [`--sort-backends`](#sort-backends)                     | [true\|false]              | `false`                 |       |
+| [`--sort-endpoints-by`](#sort-endpoints-by)             | [endpoint\|ip\|name\|random] | `endpoint`            | v0.11 |
 | [`--stats-collect-processing-period`](#stats)           | time                       | `500ms`                 | v0.10 |
 | [`--tcp-services-configmap`](#tcp-services-configmap)   | namespace/configmapname    | no tcp svc              |       |
 | [`--verify-hostname`](#verify-hostname)                 | [true\|false]              | `true`                  |       |
@@ -235,7 +236,8 @@ describes how it works.
 ## --sort-backends
 
 Defines if backend's endpoints should be sorted by name. Since v0.8 the endpoints will stay in the
-same order found in the Kubernetes' endpoint objects if `--sort-backends` is missing.
+same order found in the Kubernetes' endpoint objects if `--sort-backends` is missing. This option
+has less precedence than `--sort-endpoints-by` if both are declared.
 
 In v0.7 and older version, if `--sort-backends` is missing, HAProxy Ingress randomly shuffle endpoints
 on each reload in order to avoid requesting always the same backends just after haproxy reloads.
@@ -246,6 +248,20 @@ option, because the default value builds the server name using a numeric sequenc
 See also:
 
 * [backend-server-naming]({{% relref "keys#backend-server-naming" %}}) configuration key
+* [sort-endpoints-by]({{% relref "#sort-endpoints-by" %}}) command-line option
+
+---
+
+## --sort-endpoints-by
+
+Since v0.11
+
+Defines in which order the endpoints of a backend should be sorted.
+
+* `endpoint`: this is the default value, uses the same order declared in the Kubernetes' Endpoint objects. `ep` is an alias to `endpoint`
+* `ip`: sort endpoints by the IP and port of the destination server
+* `name`: sort the endpoints by the name given to the server, see also [backend-server-naming]({{% relref "keys#backend-server-naming" %}})
+* `random`: randomly shuffle the endpoints every time haproxy needs to be reloaded, this option avoids to always send requests to the same endpoints depending on the balancing algorithm
 
 ---
 

pkg/common/ingress/controller/controller.go

@@ -98,7 +98,7 @@ type Configuration struct {
 	UpdateStatusOnShutdown bool
 
 	BackendShards             int
-	SortBackends              bool
+	SortEndpointsBy           string
 	IgnoreIngressWithoutClass bool
 }
 

pkg/common/ingress/controller/launch.go

@@ -169,7 +169,12 @@ func NewIngressController(backend ingress.Controller) *GenericController {
 			`Defines how much files should be used to configure the haproxy backends`)
 
 		sortBackends = flags.Bool("sort-backends", false,
-			`Defines if backend's endpoints should be sorted by name. It uses the same k8s endpoint order if missing`)
+			`Defines if backend's endpoints should be sorted by name. This option has less precedence than
+		--sort-endpoints-by if both are declared.`)
+
+		sortEndpointsBy = flags.String("sort-endpoints-by", "",
+			`Defines how to sort backend's endpoints. Allowed values are: 'endpoint' - same k8s endpoint order (default);
+		'name' - server/endpoint name; 'ip' - server/endpoint IP and port; 'random' - shuffle endpoints on every haproxy reload`)
 
 		useNodeInternalIP = flags.Bool("report-node-internal-ip-address", false,
 			`Defines if the nodes IP address to be returned in the ingress status should be the internal instead of the external IP address`)
@@ -296,6 +301,18 @@ func NewIngressController(backend ingress.Controller) *GenericController {
 		glog.Fatal("Cannot use --allow-cross-namespace if --force-namespace-isolation is true")
 	}
 
+	sortEndpoints := strings.ToLower(*sortEndpointsBy)
+	if sortEndpoints == "" {
+		if *sortBackends {
+			sortEndpoints = "name"
+		} else {
+			sortEndpoints = "endpoint"
+		}
+	}
+	if !stringInSlice(sortEndpoints, []string{"ep", "endpoint", "ip", "name", "random"}) {
+		glog.Fatalf("Unsupported --sort-endpoint-by option: %s", sortEndpoints)
+	}
+
 	config := &Configuration{
 		UpdateStatus:              *updateStatus,
 		ElectionID:                *electionID,
@@ -332,7 +349,7 @@ func NewIngressController(backend ingress.Controller) *GenericController {
 		DisablePodList:            *disablePodList,
 		UpdateStatusOnShutdown:    *updateStatusOnShutdown,
 		BackendShards:             *backendShards,
-		SortBackends:              *sortBackends,
+		SortEndpointsBy:           sortEndpoints,
 		UseNodeInternalIP:         *useNodeInternalIP,
 		IgnoreIngressWithoutClass: *ignoreIngressWithoutClass,
 	}

pkg/controller/controller.go

@@ -130,7 +130,7 @@ func (hc *HAProxyController) configController() {
 		Metrics:           hc.metrics,
 		ReloadStrategy:    *hc.reloadStrategy,
 		MaxOldConfigFiles: *hc.maxOldConfigFiles,
-		SortBackends:      hc.cfg.SortBackends,
+		SortEndpointsBy:   hc.cfg.SortEndpointsBy,
 		ValidateConfig:    *hc.validateConfig,
 	}
 	hc.instance = haproxy.CreateInstance(hc.logger, instanceOptions)

pkg/haproxy/instance.go

@@ -44,7 +44,7 @@ type InstanceOptions struct {
 	MaxOldConfigFiles int
 	Metrics           types.Metrics
 	ReloadStrategy    string
-	SortBackends      bool
+	SortEndpointsBy   string
 	ValidateConfig    bool
 	// TODO Fake is used to skip real haproxy calls. Use a mock instead.
 	fake bool
@@ -258,8 +258,12 @@ func (i *instance) haproxyUpdate(timer *utils.Timer) {
 	}
 	updater := i.newDynUpdater()
 	updated := updater.update()
-	if i.options.SortBackends {
-		i.config.Backends().SortChangedEndpoints()
+	if i.options.SortEndpointsBy != "random" {
+		i.config.Backends().SortChangedEndpoints(i.options.SortEndpointsBy)
+	} else if !updated {
+		// Only shuffle if need to reload
+		i.config.Backends().ShuffleAllEndpoints()
+		timer.Tick("shuffle_endpoints")
 	}
 	if !updated || updater.cmdCnt > 0 {
 		// only need to rewrtite config files if:

pkg/haproxy/types/backend.go

@@ -18,9 +18,11 @@ package types
 
 import (
 	"fmt"
+	"math/rand"
 	"reflect"
 	"sort"
 	"strings"
+	"time"
 )
 
 // BackendID ...
@@ -92,9 +94,26 @@ func (b *Backend) addEndpoint(ip string, port int, targetRef string) *Endpoint {
 	return endpoint
 }
 
-func (b *Backend) sortEndpoints() {
-	sort.SliceStable(b.Endpoints, func(i, j int) bool {
-		return b.Endpoints[i].Name < b.Endpoints[j].Name
+func (b *Backend) sortEndpoints(sortBy string) {
+	ep := b.Endpoints
+	switch sortBy {
+	// ignoring "ep"/"endpoint" (use the k8s order) and "random" (shuffleEndpoints implements)
+	case "name":
+		sort.Slice(ep, func(i, j int) bool {
+			return ep[i].Name < ep[j].Name
+		})
+	case "ip":
+		sort.Slice(ep, func(i, j int) bool {
+			return ep[i].IP < ep[j].IP
+		})
+	}
+}
+
+func (b *Backend) shuffleEndpoints() {
+	ep := b.Endpoints
+	rand.Seed(time.Now().UnixNano())
+	rand.Shuffle(len(ep), func(i, j int) {
+		ep[i], ep[j] = ep[j], ep[i]
 	})
 }
 

pkg/haproxy/types/backends.go

@@ -146,9 +146,16 @@ func (b *Backends) ChangedShards() []int {
 }
 
 // SortChangedEndpoints ...
-func (b *Backends) SortChangedEndpoints() {
+func (b *Backends) SortChangedEndpoints(sortBy string) {
 	for _, backend := range b.itemsAdd {
-		backend.sortEndpoints()
+		backend.sortEndpoints(sortBy)
+	}
+}
+
+// ShuffleAllEndpoints ...
+func (b *Backends) ShuffleAllEndpoints() {
+	for _, backend := range b.items {
+		backend.shuffleEndpoints()
 	}
 }