refactor(probeservices): use better naming (#1628)

Calling the endpoint base URL (e.g., `https://www.example.com/`)
"endpoint" could cause confusion because usually an API endpoint is
something like `https://www.example.com/api/v1/check-in`. To obviate
this semantic issue, this diff attempts to avoid calling base URLs as
endpoint throughout the tree.

I am going to account this work as part of
ooni/backend#754 because this is one of the
possibly issues on which we can account this work. The original
conversation with @ainghazal, which prodded me to make these changes,
was related to his feedback after implementing
#1625.

internal/engine/experiment_integration_test.go

@@ -3,6 +3,7 @@ package engine
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"net/http"
 	"net/http/httptest"
 	"os"
@@ -11,6 +12,7 @@ import (
 
 	"github.com/google/go-cmp/cmp"
 	"github.com/ooni/probe-cli/v3/internal/model"
+	"github.com/ooni/probe-cli/v3/internal/probeservices"
 	"github.com/ooni/probe-cli/v3/internal/registry"
 )
 
@@ -384,7 +386,7 @@ func TestOpenReportNewClientFailure(t *testing.T) {
 		Type:    "antani",
 	}
 	err = exp.OpenReportContext(context.Background())
-	if err.Error() != "probe services: unsupported endpoint type" {
+	if !errors.Is(err, probeservices.ErrUnsupportedServiceType) {
 		t.Fatal(err)
 	}
 }

internal/engine/session.go

@@ -673,8 +673,8 @@ func (s *Session) MaybeLookupBackendsContext(ctx context.Context) error {
 	if selected == nil {
 		return ErrAllProbeServicesFailed
 	}
-	s.logger.Infof("session: using probe services: %+v", selected.Endpoint)
-	s.selectedProbeService = &selected.Endpoint
+	s.logger.Infof("session: using probe services: %+v", selected.Service)
+	s.selectedProbeService = &selected.Service
 	s.availableTestHelpers = selected.TestHelpers
 	return nil
 }

internal/engine/session_integration_test.go

@@ -483,7 +483,7 @@ func TestNewOrchestraClientProbeServicesNewClientFailure(t *testing.T) {
 		svc.Type = "antani" // should really not be supported for a long time
 	}
 	client, err := sess.newOrchestraClient(context.Background())
-	if !errors.Is(err, probeservices.ErrUnsupportedEndpoint) {
+	if !errors.Is(err, probeservices.ErrUnsupportedServiceType) {
 		t.Fatal("not the error we expected")
 	}
 	if client != nil {

internal/probeservices/benchselect.go

@@ -19,8 +19,8 @@ func Default() []model.OOAPIService {
 	}}
 }
 
-// SortEndpoints gives priority to https, then cloudfronted, then onion.
-func SortEndpoints(in []model.OOAPIService) (out []model.OOAPIService) {
+// SortServices gives priority to https, then cloudfronted, then onion.
+func SortServices(in []model.OOAPIService) (out []model.OOAPIService) {
 	for _, entry := range in {
 		if entry.Type == "https" {
 			out = append(out, entry)
@@ -39,7 +39,7 @@ func SortEndpoints(in []model.OOAPIService) (out []model.OOAPIService) {
 	return
 }
 
-// OnlyHTTPS returns the HTTPS endpoints only.
+// OnlyHTTPS returns the HTTPS services only.
 func OnlyHTTPS(in []model.OOAPIService) (out []model.OOAPIService) {
 	for _, entry := range in {
 		if entry.Type == "https" {
@@ -49,9 +49,9 @@ func OnlyHTTPS(in []model.OOAPIService) (out []model.OOAPIService) {
 	return
 }
 
-// OnlyFallbacks returns the fallback endpoints only.
+// OnlyFallbacks returns the fallback services only.
 func OnlyFallbacks(in []model.OOAPIService) (out []model.OOAPIService) {
-	for _, entry := range SortEndpoints(in) {
+	for _, entry := range SortServices(in) {
 		if entry.Type != "https" {
 			out = append(out, entry)
 		}
@@ -67,15 +67,16 @@ type Candidate struct {
 	// Err indicates whether the service works.
 	Err error
 
-	// Endpoint is the service endpoint.
-	Endpoint model.OOAPIService
+	// Service is the service to use.
+	Service model.OOAPIService
 
-	// TestHelpers contains the data returned by the endpoint.
+	// TestHelpers contains the data returned by the service when
+	// querying the /api/v1/test-helpers API endpoint.
 	TestHelpers map[string][]model.OOAPIService
 }
 
 func (c *Candidate) try(ctx context.Context, sess Session) {
-	client, err := NewClient(sess, c.Endpoint)
+	client, err := NewClient(sess, c.Service)
 	if err != nil {
 		c.Err = err
 		return
@@ -85,11 +86,11 @@ func (c *Candidate) try(ctx context.Context, sess Session) {
 	c.Duration = time.Since(start)
 	c.Err = err
 	c.TestHelpers = testhelpers
-	sess.Logger().Debugf("probe services: %+v: %+v %s", c.Endpoint, err, c.Duration)
+	sess.Logger().Debugf("probe services: %+v: %+v %s", c.Service, err, c.Duration)
 }
 
 func try(ctx context.Context, sess Session, svc model.OOAPIService) *Candidate {
-	candidate := &Candidate{Endpoint: svc}
+	candidate := &Candidate{Service: svc}
 	candidate.try(ctx, sess)
 	return candidate
 }

internal/probeservices/probeservices.go

@@ -1,6 +1,6 @@
 // Package probeservices contains code to contact OONI probe services.
 //
-// The probe services are HTTPS endpoints distributed across a bunch of data
+// The probe services are HTTPS services distributed across a bunch of data
 // centres implementing a bunch of OONI APIs. When started, OONI will benchmark
 // the available probe services and select the fastest one. Eventually all the
 // possible OONI APIs will run as probe services.
@@ -32,8 +32,8 @@ import (
 )
 
 var (
-	// ErrUnsupportedEndpoint indicates that we don't support this endpoint type.
-	ErrUnsupportedEndpoint = errors.New("probe services: unsupported endpoint type")
+	// ErrUnsupportedServiceType indicates that we don't support this service type.
+	ErrUnsupportedServiceType = errors.New("probe services: unsupported service type")
 
 	// ErrUnsupportedCloudFrontAddress indicates that we don't support this
 	// cloudfront address (e.g. wrong scheme, presence of port).
@@ -90,11 +90,11 @@ func (c Client) GetCredsAndAuth() (*model.OOAPILoginCredentials, *model.OOAPILog
 	return creds, auth, nil
 }
 
-// NewClient creates a new client for the specified probe services endpoint. This
-// function fails, e.g., we don't support the specified endpoint.
-func NewClient(sess Session, endpoint model.OOAPIService) (*Client, error) {
+// NewClient creates a new client for the specified probe services service. This
+// function fails, e.g., we don't support the specified service.
+func NewClient(sess Session, service model.OOAPIService) (*Client, error) {
 	client := &Client{
-		BaseURL:       endpoint.Address,
+		BaseURL:       service.Address,
 		HTTPClient:    sess.DefaultHTTPClient(),
 		Host:          "",
 		KVStore:       sess.KeyValueStore(),
@@ -104,7 +104,7 @@ func NewClient(sess Session, endpoint model.OOAPIService) (*Client, error) {
 		StateFile:     NewStateFile(sess.KeyValueStore()),
 		UserAgent:     sess.UserAgent(),
 	}
-	switch endpoint.Type {
+	switch service.Type {
 	case "https":
 		return client, nil
 	case "cloudfront":
@@ -119,13 +119,13 @@ func NewClient(sess Session, endpoint model.OOAPIService) (*Client, error) {
 			return nil, ErrUnsupportedCloudFrontAddress
 		}
 		client.Host = URL.Hostname()
-		URL.Host = endpoint.Front
+		URL.Host = service.Front
 		client.BaseURL = URL.String()
 		if _, err := url.Parse(client.BaseURL); err != nil {
 			return nil, err
 		}
 		return client, nil
 	default:
-		return nil, ErrUnsupportedEndpoint
+		return nil, ErrUnsupportedServiceType
 	}
 }