Add NGINX configuration for UpstreamSettingsPolicy (#2877)

Translate data plane intermediary UpstreamSettingsPolicy configuration into NGINX configuration.

Problem: I want the data plane configuration generated from my UpstreamSettingsPolicy to be translated 
into NGINX Configuration.

Solution: Translate the data plane UpstreamSettingsPolicy configuration into NGINX configuration.

Testing: Unit tests.

apis/v1alpha1/policy_methods.go

@@ -31,3 +31,15 @@ func (p *ObservabilityPolicy) GetPolicyStatus() v1alpha2.PolicyStatus {
 func (p *ObservabilityPolicy) SetPolicyStatus(status v1alpha2.PolicyStatus) {
 	p.Status = status
 }
+
+func (p *UpstreamSettingsPolicy) GetTargetRefs() []v1alpha2.LocalPolicyTargetReference {
+	return p.Spec.TargetRefs
+}
+
+func (p *UpstreamSettingsPolicy) GetPolicyStatus() v1alpha2.PolicyStatus {
+	return p.Status
+}
+
+func (p *UpstreamSettingsPolicy) SetPolicyStatus(status v1alpha2.PolicyStatus) {
+	p.Status = status
+}

config/crd/bases/gateway.nginx.org_upstreamsettingspolicies.yaml

@@ -3,7 +3,7 @@ apiVersion: apiextensions.k8s.io/v1
 kind: CustomResourceDefinition
 metadata:
   annotations:
-    controller-gen.kubebuilder.io/version: v0.16.2
+    controller-gen.kubebuilder.io/version: v0.16.5
   labels:
     gateway.networking.k8s.io/policy: direct
   name: upstreamsettingspolicies.gateway.nginx.org
@@ -76,13 +76,13 @@ spec:
                       Time defines the maximum time during which requests can be processed through one keep-alive connection.
                       After this time is reached, the connection is closed following the subsequent request processing.
                       Directive: https://nginx.org/en/docs/http/ngx_http_upstream_module.html#keepalive_time
-                    pattern: ^\d{1,4}(ms|s)?$
+                    pattern: ^[0-9]{1,4}(ms|s|m|h)?$
                     type: string
                   timeout:
                     description: |-
                       Timeout defines the keep-alive timeout for upstreams.
                       Directive: https://nginx.org/en/docs/http/ngx_http_upstream_module.html#keepalive_timeout
-                    pattern: ^\d{1,4}(ms|s)?$
+                    pattern: ^[0-9]{1,4}(ms|s|m|h)?$
                     type: string
                 type: object
               targetRefs:

internal/mode/static/nginx/config/generator.go

@@ -6,9 +6,11 @@ import (
 	"github.com/go-logr/logr"
 
 	ngfConfig "github.com/nginxinc/nginx-gateway-fabric/internal/mode/static/config"
+	"github.com/nginxinc/nginx-gateway-fabric/internal/mode/static/nginx/config/http"
 	"github.com/nginxinc/nginx-gateway-fabric/internal/mode/static/nginx/config/policies"
 	"github.com/nginxinc/nginx-gateway-fabric/internal/mode/static/nginx/config/policies/clientsettings"
 	"github.com/nginxinc/nginx-gateway-fabric/internal/mode/static/nginx/config/policies/observability"
+	"github.com/nginxinc/nginx-gateway-fabric/internal/mode/static/nginx/config/policies/upstreamsettings"
 	"github.com/nginxinc/nginx-gateway-fabric/internal/mode/static/nginx/file"
 	"github.com/nginxinc/nginx-gateway-fabric/internal/mode/static/state/dataplane"
 )
@@ -131,7 +133,10 @@ func (g GeneratorImpl) executeConfigTemplates(
 ) []file.File {
 	fileBytes := make(map[string][]byte)
 
-	for _, execute := range g.getExecuteFuncs(generator) {
+	httpUpstreams := g.createUpstreams(conf.Upstreams, upstreamsettings.NewProcessor())
+	keepAliveCheck := newKeepAliveChecker(httpUpstreams)
+
+	for _, execute := range g.getExecuteFuncs(generator, httpUpstreams, keepAliveCheck) {
 		results := execute(conf)
 		for _, res := range results {
 			fileBytes[res.dest] = append(fileBytes[res.dest], res.data...)
@@ -156,12 +161,16 @@ func (g GeneratorImpl) executeConfigTemplates(
 	return files
 }
 
-func (g GeneratorImpl) getExecuteFuncs(generator policies.Generator) []executeFunc {
+func (g GeneratorImpl) getExecuteFuncs(
+	generator policies.Generator,
+	upstreams []http.Upstream,
+	keepAliveCheck keepAliveChecker,
+) []executeFunc {
 	return []executeFunc{
 		executeMainConfig,
 		executeBaseHTTPConfig,
-		g.newExecuteServersFunc(generator),
-		g.executeUpstreams,
+		g.newExecuteServersFunc(generator, keepAliveCheck),
+		newExecuteUpstreamsFunc(upstreams),
 		executeSplitClients,
 		executeMaps,
 		executeTelemetry,

internal/mode/static/nginx/config/http/config.go

@@ -1,6 +1,8 @@
 package http
 
-import "github.com/nginxinc/nginx-gateway-fabric/internal/mode/static/nginx/config/shared"
+import (
+	"github.com/nginxinc/nginx-gateway-fabric/internal/mode/static/nginx/config/shared"
+)
 
 const (
 	InternalRoutePathPrefix = "/_ngf-internal"
@@ -82,9 +84,18 @@ const (
 
 // Upstream holds all configuration for an HTTP upstream.
 type Upstream struct {
-	Name     string
-	ZoneSize string // format: 512k, 1m
-	Servers  []UpstreamServer
+	Name      string
+	ZoneSize  string // format: 512k, 1m
+	KeepAlive UpstreamKeepAlive
+	Servers   []UpstreamServer
+}
+
+// UpstreamKeepAlive holds the keepalive configuration for an HTTP upstream.
+type UpstreamKeepAlive struct {
+	Time        string
+	Timeout     string
+	Connections int32
+	Requests    int32
 }
 
 // UpstreamServer holds all configuration for an HTTP upstream server.

internal/mode/static/nginx/config/policies/upstreamsettings/processor.go

@@ -0,0 +1,67 @@
+package upstreamsettings
+
+import (
+	ngfAPI "github.com/nginxinc/nginx-gateway-fabric/apis/v1alpha1"
+	"github.com/nginxinc/nginx-gateway-fabric/internal/mode/static/nginx/config/http"
+	"github.com/nginxinc/nginx-gateway-fabric/internal/mode/static/nginx/config/policies"
+)
+
+// Processor processes UpstreamSettingsPolicies.
+type Processor struct{}
+
+// UpstreamSettings contains settings from UpstreamSettingsPolicy.
+type UpstreamSettings struct {
+	// ZoneSize is the zone size setting.
+	ZoneSize string
+	// KeepAlive contains the keepalive settings.
+	KeepAlive http.UpstreamKeepAlive
+}
+
+// NewProcessor returns a new Processor.
+func NewProcessor() Processor {
+	return Processor{}
+}
+
+// Process processes policies into an UpstreamSettings object. The policies are already validated and are guaranteed
+// to not contain overlapping settings. This method merges all fields in the policies into a single UpstreamSettings
+// object.
+func (g Processor) Process(pols []policies.Policy) UpstreamSettings {
+	return processPolicies(pols)
+}
+
+func processPolicies(pols []policies.Policy) UpstreamSettings {
+	upstreamSettings := UpstreamSettings{}
+
+	for _, pol := range pols {
+		usp, ok := pol.(*ngfAPI.UpstreamSettingsPolicy)
+		if !ok {
+			continue
+		}
+
+		// we can assume that there will be no instance of two or more policies setting the same
+		// field for the same service
+		if usp.Spec.ZoneSize != nil {
+			upstreamSettings.ZoneSize = string(*usp.Spec.ZoneSize)
+		}
+
+		if usp.Spec.KeepAlive != nil {
+			if usp.Spec.KeepAlive.Connections != nil {
+				upstreamSettings.KeepAlive.Connections = *usp.Spec.KeepAlive.Connections
+			}
+
+			if usp.Spec.KeepAlive.Requests != nil {
+				upstreamSettings.KeepAlive.Requests = *usp.Spec.KeepAlive.Requests
+			}
+
+			if usp.Spec.KeepAlive.Time != nil {
+				upstreamSettings.KeepAlive.Time = string(*usp.Spec.KeepAlive.Time)
+			}
+
+			if usp.Spec.KeepAlive.Timeout != nil {
+				upstreamSettings.KeepAlive.Timeout = string(*usp.Spec.KeepAlive.Timeout)
+			}
+		}
+	}
+
+	return upstreamSettings
+}