fix(aigateway): add backend upstream test endpoint to avoid frontend CORS (#1244)

Co-authored-by: cemeng <cemengzhang@gmail.com>

Author: Rader

_mocks/opencsg.com/csghub-server/component/mock_LLMServiceComponent.go

@@ -172,3 +172,31 @@ type UpdateUpstreamReq struct {
 	Tags                  *map[string]string `json:"tags"`
 	Metadata              *map[string]any    `json:"metadata"`
 }
+
+// TestUpstreamReq is the request to test connectivity to an upstream endpoint.
+// The upstream is identified by its database ID; the backend fetches the
+// upstream's URL, model name and auth header from the database so that the
+// frontend never needs to send credentials or perform cross-origin requests.
+type TestUpstreamReq struct {
+	ID int64 `json:"id" binding:"required"`
+}
+
+// TestUpstreamResult is the result of an upstream connectivity test.
+// The request summary is masked so that sensitive header values (such as
+// API keys) are never leaked to the frontend.
+type TestUpstreamResult struct {
+	// Request is the masked request summary (url, method, headers, body).
+	Request string `json:"request"`
+	// OK indicates whether the upstream returned a 2xx status code.
+	OK bool `json:"ok"`
+	// Status is the HTTP status code returned by the upstream.
+	Status int `json:"status"`
+	// StatusText is the HTTP status text returned by the upstream.
+	StatusText string `json:"status_text"`
+	// Content is the extracted text content from the upstream response.
+	Content string `json:"content"`
+	// ResponseBody is the raw response body from the upstream.
+	ResponseBody string `json:"response_body"`
+	// Error is the error message when the test fails (e.g. timeout, network error).
+	Error string `json:"error,omitempty"`
+}

common/types/llm_service.go

@@ -36,6 +36,11 @@ type LLMServiceComponent interface {
 	UpdateUpstream(ctx context.Context, req *types.UpdateUpstreamReq) (*types.UpstreamConfig, error)
 	// DeleteUpstream deletes an upstream by ID.
 	DeleteUpstream(ctx context.Context, id int64) error
+	// TestUpstream tests connectivity to an upstream endpoint by ID. It fetches
+	// the upstream config from the database, sends a simple "hi" prompt to the
+	// upstream URL (supporting /chat/completions and /responses endpoints), and
+	// returns the masked request summary, response status, body and content.
+	TestUpstream(ctx context.Context, req *types.TestUpstreamReq) (*types.TestUpstreamResult, error)
 }
 
 type llmServiceComponentImpl struct {

component/llm_service.go

@@ -0,0 +1,269 @@
+
+package component
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"log/slog"
+	"net/http"
+	"strings"
+	"time"
+
+	"opencsg.com/csghub-server/common/errorx"
+	"opencsg.com/csghub-server/common/types"
+)
+
+// upstreamTestTimeout is the maximum duration allowed for an upstream
+// connectivity test request.
+const upstreamTestTimeout = 30 * time.Second
+
+// maskedAuthSecret is the placeholder used to redact sensitive header values
+// in the request summary returned to the frontend.
+const maskedAuthSecret = "................."
+
+// endpointChatCompletions and endpointResponses are the two supported
+// upstream endpoint path suffixes.
+const (
+	endpointChatCompletions = "/chat/completions"
+	endpointResponses       = "/responses"
+)
+
+// testEndpointKind describes which protocol the upstream URL speaks.
+type testEndpointKind int
+
+const (
+	endpointKindUnsupported testEndpointKind = iota
+	endpointKindChatCompletions
+	endpointKindResponses
+)
+
+// detectEndpointKind inspects the upstream URL path and returns the
+// supported endpoint kind. Only /chat/completions and /responses are
+// supported; anything else returns endpointKindUnsupported.
+func detectEndpointKind(rawURL string) testEndpointKind {
+	// Trim query string and fragment before checking the path suffix.
+	u := rawURL
+	if idx := strings.IndexAny(u, "?#"); idx >= 0 {
+		u = u[:idx]
+	}
+	u = strings.TrimRight(u, "/")
+	switch {
+	case strings.HasSuffix(u, endpointChatCompletions):
+		return endpointKindChatCompletions
+	case strings.HasSuffix(u, endpointResponses):
+		return endpointKindResponses
+	default:
+		return endpointKindUnsupported
+	}
+}
+
+// parseAuthHeader parses the upstream auth_header field into a map of
+// HTTP headers. The auth_header is either a plain "Bearer xxx" string or
+// a JSON object string like {"Authorization":"Bearer xxx"}.
+func parseAuthHeader(authHeader string) (map[string]string, error) {
+	trimmed := strings.TrimSpace(authHeader)
+	if trimmed == "" {
+		return map[string]string{}, nil
+	}
+
+	var parsed map[string]string
+	if err := json.Unmarshal([]byte(trimmed), &parsed); err != nil {
+		// Not a JSON object; treat as a bare Authorization value.
+		return map[string]string{
+			"Authorization": trimmed,
+		}, nil
+	}
+
+	headers := make(map[string]string, len(parsed))
+	for k, v := range parsed {
+		key := strings.TrimSpace(k)
+		if key == "" {
+			continue
+		}
+		headers[key] = v
+	}
+	return headers, nil
+}
+
+// maskRequestHeaders returns a copy of the headers with sensitive values
+// redacted. Only Content-Type is preserved verbatim; all other values
+// (including Authorization / apikey) are masked.
+func maskRequestHeaders(headers map[string]string) map[string]string {
+	masked := make(map[string]string, len(headers))
+	for k, v := range headers {
+		switch strings.ToLower(k) {
+		case "content-type":
+			masked[k] = v
+		default:
+			masked[k] = maskedAuthSecret
+		}
+	}
+	return masked
+}
+
+// buildTestRequestBody constructs the request body for the given endpoint
+// kind. A simple "hi" prompt is used for both protocols.
+func buildTestRequestBody(kind testEndpointKind, modelName string) (map[string]any, error) {
+	switch kind {
+	case endpointKindChatCompletions:
+		return map[string]any{
+			"model":    modelName,
+			"messages": []map[string]string{{"role": "user", "content": "hi"}},
+			"stream":   false,
+		}, nil
+	case endpointKindResponses:
+		return map[string]any{
+			"model":  modelName,
+			"input":  "hi",
+			"stream": false,
+		}, nil
+	default:
+		return nil, fmt.Errorf("unsupported upstream endpoint, only %s and %s are supported", endpointChatCompletions, endpointResponses)
+	}
+}
+
+// requestSummary is the masked request representation sent to the frontend.
+type requestSummary struct {
+	URL     string            `json:"url"`
+	Method  string            `json:"method"`
+	Headers map[string]string `json:"headers"`
+	Body    map[string]any    `json:"body"`
+}
+
+// doUpstreamTest performs the HTTP request against the upstream and returns
+// the test result. It is split from TestUpstream so it can be unit tested
+// with an injectable http.Client.
+func doUpstreamTest(ctx context.Context, client *http.Client, url string, kind testEndpointKind, modelName string, authHeaders map[string]string) (*types.TestUpstreamResult, error) {
+	body, err := buildTestRequestBody(kind, modelName)
+	if err != nil {
+		return nil, err
+	}
+
+	bodyBytes, err := json.Marshal(body)
+	if err != nil {
+		return nil, fmt.Errorf("failed to marshal request body: %w", err)
+	}
+
+	requestHeaders := map[string]string{
+		"Content-Type": "application/json",
+	}
+	for k, v := range authHeaders {
+		requestHeaders[k] = v
+	}
+
+	summary := requestSummary{
+		URL:     url,
+		Method:  http.MethodPost,
+		Headers: maskRequestHeaders(requestHeaders),
+		Body:    body,
+	}
+	summaryBytes, _ := json.MarshalIndent(summary, "", "  ")
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(bodyBytes))
+	if err != nil {
+		return &types.TestUpstreamResult{
+			Request: string(summaryBytes),
+			Error:   err.Error(),
+		}, nil
+	}
+	for k, v := range requestHeaders {
+		req.Header.Set(k, v)
+	}
+
+	resp, err := client.Do(req)
+	if err != nil {
+		return &types.TestUpstreamResult{
+			Request: string(summaryBytes),
+			Error:   err.Error(),
+		}, nil
+	}
+	defer resp.Body.Close()
+
+	rawBytes, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return &types.TestUpstreamResult{
+			Request:     string(summaryBytes),
+			OK:          false,
+			Status:      resp.StatusCode,
+			StatusText:  resp.Status,
+			ResponseBody: "",
+			Error:       fmt.Sprintf("failed to read response body: %v", err),
+		}, nil
+	}
+	rawText := string(rawBytes)
+
+	var prettyBody string
+	var jsonObj map[string]any
+	if json.Unmarshal(rawBytes, &jsonObj) == nil {
+		pretty, _ := json.MarshalIndent(jsonObj, "", "  ")
+		prettyBody = string(pretty)
+	} else {
+		prettyBody = rawText
+	}
+
+	return &types.TestUpstreamResult{
+		Request:      string(summaryBytes),
+		OK:           resp.StatusCode >= 200 && resp.StatusCode < 300,
+		Status:       resp.StatusCode,
+		StatusText:   resp.Status,
+		Content:      rawText,
+		ResponseBody: prettyBody,
+	}, nil
+}
+
+// TestUpstream tests connectivity to an upstream endpoint by ID.
+func (s *llmServiceComponentImpl) TestUpstream(ctx context.Context, req *types.TestUpstreamReq) (*types.TestUpstreamResult, error) {
+	dbUp, err := s.upstreamStore.GetByID(ctx, req.ID)
+	if err != nil {
+		return nil, fmt.Errorf("upstream not found: %w", err)
+	}
+
+	url := strings.TrimSpace(dbUp.URL)
+	if url == "" {
+		return nil, fmt.Errorf("upstream url is empty")
+	}
+	modelName := strings.TrimSpace(dbUp.ModelName)
+	if modelName == "" {
+		return nil, fmt.Errorf("upstream model_name is empty")
+	}
+
+	kind := detectEndpointKind(url)
+	if kind == endpointKindUnsupported {
+		return nil, errorx.ReqParamInvalid(
+			fmt.Errorf("unsupported upstream endpoint, only %s and %s are supported", endpointChatCompletions, endpointResponses),
+			nil,
+		)
+	}
+
+	authHeaders, err := parseAuthHeader(dbUp.AuthHeader)
+	if err != nil {
+		return nil, fmt.Errorf("invalid auth_header: %w", err)
+	}
+
+	testCtx, cancel := context.WithTimeout(ctx, upstreamTestTimeout)
+	defer cancel()
+
+	client := &http.Client{Timeout: upstreamTestTimeout}
+
+	slog.InfoContext(ctx, "testing upstream connection",
+		slog.Int64("upstream_id", dbUp.ID),
+		slog.String("url", url),
+		slog.String("endpoint_kind", endpointKindString(kind)),
+	)
+
+	return doUpstreamTest(testCtx, client, url, kind, modelName, authHeaders)
+}
+
+func endpointKindString(k testEndpointKind) string {
+	switch k {
+	case endpointKindChatCompletions:
+		return endpointChatCompletions
+	case endpointKindResponses:
+		return endpointResponses
+	default:
+		return "unsupported"
+	}
+}