feat(core): add addr fetch logic in gcp resolver

go.mod

@@ -8,6 +8,7 @@ require (
 	github.com/gorilla/websocket v1.5.0
 	go.mongodb.org/mongo-driver v1.9.1
 	go.uber.org/zap v1.21.0
+	golang.org/x/sync v0.0.0-20220601150217-0de741cfad7f
 )
 
 require (
@@ -31,7 +32,6 @@ require (
 	go.uber.org/atomic v1.9.0 // indirect
 	go.uber.org/multierr v1.8.0 // indirect
 	golang.org/x/crypto v0.0.0-20220622213112-05595931fe9d // indirect
-	golang.org/x/sync v0.0.0-20220601150217-0de741cfad7f // indirect
 	golang.org/x/text v0.3.7 // indirect
 	gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 // indirect
 	gopkg.in/yaml.v2 v2.4.0 // indirect

main.go

@@ -32,25 +32,13 @@ func main() {
 	resolver := discovery.NewResolver()
 	go func() {
 		time.Sleep(time.Second * 2)
-		fmt.Println("Attempting fetches...")
+		fmt.Println("Attempting fetch...")
 
-		pid, errP := resolver.GetProjectID(ctx)
-		if errP != nil {
-			panic("failed to get project id:" + errP.Error())
+		addr, err := resolver.GetAddress(ctx)
+		if err != nil {
+			panic("failed to get addr:" + err.Error())
 		}
-		fmt.Println(">>>> pid:", pid)
-
-		region, errR := resolver.GetRegion(ctx)
-		if errR != nil {
-			panic("failed to get region:" + errR.Error())
-		}
-		fmt.Println(">>>> region:", region)
-
-		token, errT := resolver.GetToken(ctx)
-		if errT != nil {
-			panic("failed to get token:" + errT.Error())
-		}
-		fmt.Println(">>>> token:", token)
+		fmt.Println(">>>> addr:", addr)
 	}()
 
 	// Setting core dependencies.

src/impl/discovery/resolver.go

@@ -2,11 +2,17 @@ package discovery
 
 import (
 	"context"
+	"encoding/json"
+	"errors"
 	"fmt"
 	"io/ioutil"
 	"net/http"
+	"os"
+	"strings"
 
 	"github.com/shivanshkc/rosenbridge/src/utils/httputils"
+
+	"golang.org/x/sync/errgroup"
 )
 
 const (
@@ -35,7 +41,7 @@ func (r *ResolverCloudRun) Resolve() string {
 	return r.discoveryAddr
 }
 
-func (r *ResolverCloudRun) GetProjectID(ctx context.Context) (string, error) {
+func (r *ResolverCloudRun) getProjectID(ctx context.Context) (string, error) {
 	endpoint := fmt.Sprintf("%s%s", gcpMetadataBaseURL, gcpProjectIDURL)
 	// Forming the HTTP request.
 	request, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
@@ -68,7 +74,7 @@ func (r *ResolverCloudRun) GetProjectID(ctx context.Context) (string, error) {
 	return string(projectIDBytes), nil
 }
 
-func (r *ResolverCloudRun) GetRegion(ctx context.Context) (string, error) {
+func (r *ResolverCloudRun) getRegion(ctx context.Context) (string, error) {
 	endpoint := fmt.Sprintf("%s%s", gcpMetadataBaseURL, gcpRegionURL)
 	// Forming the HTTP request.
 	request, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
@@ -98,11 +104,15 @@ func (r *ResolverCloudRun) GetRegion(ctx context.Context) (string, error) {
 		return "", fmt.Errorf("error in ioutil.Readall call: %w", err)
 	}
 
-	fmt.Println("Region bytes:", string(regionBytes))
-	return string(regionBytes), nil
+	// Region is of the form: "projects/948115683669/regions/us-central1".
+	// So, we split it by "/" character and then take the last element.
+	regionElements := strings.Split(string(regionBytes), "/")
+	region := regionElements[len(regionElements)-1]
+
+	return region, nil
 }
 
-func (r *ResolverCloudRun) GetToken(ctx context.Context) (string, error) {
+func (r *ResolverCloudRun) getToken(ctx context.Context) (string, error) {
 	endpoint := fmt.Sprintf("%s%s", gcpMetadataBaseURL, gcpTokenURL)
 	// Forming the HTTP request.
 	request, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
@@ -126,12 +136,117 @@ func (r *ResolverCloudRun) GetToken(ctx context.Context) (string, error) {
 		return "", fmt.Errorf("response has unsuccessful status: %d", response.StatusCode)
 	}
 
+	// This is the expected response body structure.
+	bodyStruct := &struct {
+		AccessToken string `json:"access_token"`
+		ExpiresIn   int    `json:"expires_in"`
+		TokenType   string `json:"token_type"`
+	}{}
+
+	// Decoding the response body into the intended struct.
+	if err := json.NewDecoder(response.Body).Decode(bodyStruct); err != nil {
+		return "", fmt.Errorf("error in json.NewDecoder(...).Decode call: %w", err)
+	}
+
+	// Returning the access token.
+	return bodyStruct.AccessToken, nil
+}
+
+func (r *ResolverCloudRun) GetAddress(ctx context.Context) (string, error) {
+	kService := os.Getenv("K_SERVICE")
+	if kService == "" {
+		return "", errors.New("K_SERVICE env var is empty")
+	}
+
+	// Creating an err-group to manage multiple goroutines.
+	eGroup, eCtx := errgroup.WithContext(ctx)
+
+	// Creating a channel to receive the project ID.
+	projectIDChan := make(chan string, 1)
+	defer close(projectIDChan)
+
+	// Project ID goroutine.
+	eGroup.Go(func() error {
+		projectID, err := r.getProjectID(eCtx)
+		if err != nil {
+			return fmt.Errorf("error in getProjectID call: %w", err)
+		}
+
+		projectIDChan <- projectID
+		return nil
+	})
+
+	// Creating a channel to receive the region.
+	regionChan := make(chan string, 1)
+	defer close(regionChan)
+
+	// Region goroutine.
+	eGroup.Go(func() error {
+		region, err := r.getRegion(eCtx)
+		if err != nil {
+			return fmt.Errorf("error in getRegion call: %w", err)
+		}
+
+		regionChan <- region
+		return nil
+	})
+
+	// Creating a channel to receive the token.
+	tokenChan := make(chan string, 1)
+	defer close(tokenChan)
+
+	// Region goroutine.
+	eGroup.Go(func() error {
+		token, err := r.getToken(eCtx)
+		if err != nil {
+			return fmt.Errorf("error in getToken call: %w", err)
+		}
+
+		tokenChan <- token
+		return nil
+	})
+
+	// Awaiting goroutine completions.
+	if err := eGroup.Wait(); err != nil {
+		return "", fmt.Errorf("error in eGroup.Wait call: %w", err)
+	}
+
+	// Retrieving the values from channels.
+	projectID, region, token := <-projectIDChan, <-regionChan, <-tokenChan
+
+	// Forming the API route.
+	endpoint := fmt.Sprintf("https://%s-run.googleapis.com/apis/serving.knative.dev/v1/namespaces/%s/services/%s",
+		region, projectID, kService)
+
+	// Forming the HTTP request.
+	request, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
+	if err != nil {
+		return "", fmt.Errorf("error in http.NewRequestWithContext call: %w", err)
+	}
+
+	// Setting the auth header.
+	request.Header.Set("authorization", fmt.Sprintf("Bearer %s", token))
+
+	// Creating the HTTP client.
+	client := &http.Client{}
+	// Executing the request.
+	response, err := client.Do(request)
+	if err != nil {
+		return "", fmt.Errorf("error in client.Do call: %w", err)
+	}
+	// Closing response body upon function return.
+	defer func() { _ = response.Body.Close() }()
+	// Handling unsuccessful responses.
+	if httputils.Is2xx(response.StatusCode) {
+		return "", fmt.Errorf("response has unsuccessful status: %d", response.StatusCode)
+	}
+
 	// Reading the response body into a byte slice.
-	tokenBytes, err := ioutil.ReadAll(response.Body)
+	addrBytes, err := ioutil.ReadAll(response.Body)
 	if err != nil {
 		return "", fmt.Errorf("error in ioutil.Readall call: %w", err)
 	}
 
-	fmt.Println("token bytes:", string(tokenBytes))
-	return string(tokenBytes), nil
+	fmt.Println("Addr bytes:", string(addrBytes))
+	return string(addrBytes), nil
 }