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ChrisJBurnsclaude
ChrisJBurns
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claude
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Split OTLP endpoint path to fix Langfuse/LangSmith integration (#4815)
* Split OTLP endpoint path to fix Langfuse/LangSmith integration The OTLP HTTP SDK's WithEndpoint() only accepts host:port, but users need to include a path for platforms like Langfuse and LangSmith. The path component was being URL-encoded, breaking requests. Parse the endpoint into host:port and path, using WithURLPath() for the path. Fixes #4811 Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com> * Address review feedback on OTLP endpoint path fix - Strip http:// and https:// prefixes defensively in splitEndpointPath so the CLI path (which skips NormalizeTelemetryConfig) works correctly - Extract "/v1/traces" and "/v1/metrics" as package-level constants - Add test cases: bare trailing slash, scheme-prefixed endpoints - Restore error-path coverage for metrics exporter (invalid CA cert) Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com> * Document OTLP path suffix constants with spec reference Link to the OTLP/HTTP spec and explain why we need to append these suffixes manually when a custom base path is provided. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com> --------- Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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6 files changed

Lines changed: 174 additions & 14 deletions

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‎pkg/telemetry/providers/otlp/endpoint.go‎

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@@ -0,0 +1,37 @@
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// SPDX-FileCopyrightText: Copyright 2025 Stacklok, Inc.
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// SPDX-License-Identifier: Apache-2.0
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package otlp
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import "strings"
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// Default URL path suffixes for the OTLP/HTTP protocol, as defined in the
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// OpenTelemetry specification:
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// https://opentelemetry.io/docs/specs/otlp/#otlphttp-request
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//
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// The Go OTLP SDK normally appends these automatically. However, when the user
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// provides a custom base path (e.g. "/api/public/otel" for Langfuse), we must
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// call WithURLPath which replaces the entire path. In that case we concatenate
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// the base path with the appropriate suffix ourselves (e.g.
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// "/api/public/otel" + "/v1/traces").
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const (
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otlpTracesPath = "/v1/traces"
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otlpMetricsPath = "/v1/metrics"
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)
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// splitEndpointPath separates an OTLP endpoint string into its host:port and
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// path components. If no path is present, basePath is empty.
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//
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// The function defensively strips http:// and https:// prefixes so it works
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// correctly even when the scheme has not been removed upstream (e.g. the CLI
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// path, which does not call NormalizeTelemetryConfig).
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func splitEndpointPath(endpoint string) (hostPort, basePath string) {
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endpoint = strings.TrimPrefix(endpoint, "https://")
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endpoint = strings.TrimPrefix(endpoint, "http://")
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idx := strings.Index(endpoint, "/")
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if idx < 0 {
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return endpoint, ""
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}
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return endpoint[:idx], strings.TrimRight(endpoint[idx:], "/")
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}

‎pkg/telemetry/providers/otlp/endpoint_test.go‎

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// SPDX-FileCopyrightText: Copyright 2025 Stacklok, Inc.
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// SPDX-License-Identifier: Apache-2.0
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package otlp
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import (
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"testing"
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"github.com/stretchr/testify/assert"
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)
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func TestSplitEndpointPath(t *testing.T) {
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t.Parallel()
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tests := []struct {
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name string
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endpoint string
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wantHostPort string
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wantBasePath string
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}{
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{
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name: "host and port only",
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endpoint: "localhost:4318",
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wantHostPort: "localhost:4318",
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wantBasePath: "",
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},
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{
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name: "hostname without port",
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endpoint: "otel-collector.local",
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wantHostPort: "otel-collector.local",
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wantBasePath: "",
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},
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{
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name: "Langfuse endpoint with path",
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endpoint: "cloud.langfuse.com/api/public/otel",
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wantHostPort: "cloud.langfuse.com",
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wantBasePath: "/api/public/otel",
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},
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{
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name: "LangSmith endpoint with port and path",
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endpoint: "smith.langchain.com:443/api/v1/otel",
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wantHostPort: "smith.langchain.com:443",
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wantBasePath: "/api/v1/otel",
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},
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{
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name: "trailing slash stripped",
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endpoint: "cloud.langfuse.com/api/public/otel/",
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wantHostPort: "cloud.langfuse.com",
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wantBasePath: "/api/public/otel",
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},
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{
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name: "host:port with trailing slash only",
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endpoint: "localhost:4318/",
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wantHostPort: "localhost:4318",
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wantBasePath: "",
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},
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{
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name: "https scheme stripped before splitting",
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endpoint: "https://cloud.langfuse.com/api/public/otel",
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wantHostPort: "cloud.langfuse.com",
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wantBasePath: "/api/public/otel",
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},
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{
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name: "http scheme stripped before splitting",
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endpoint: "http://localhost:4318",
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wantHostPort: "localhost:4318",
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wantBasePath: "",
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},
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{
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name: "https scheme with host only",
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endpoint: "https://api.honeycomb.io",
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wantHostPort: "api.honeycomb.io",
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wantBasePath: "",
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},
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{
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name: "empty string",
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endpoint: "",
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wantHostPort: "",
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wantBasePath: "",
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},
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}
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for _, tt := range tests {
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t.Run(tt.name, func(t *testing.T) {
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t.Parallel()
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hostPort, basePath := splitEndpointPath(tt.endpoint)
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assert.Equal(t, tt.wantHostPort, hostPort)
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assert.Equal(t, tt.wantBasePath, basePath)
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})
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}
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}

‎pkg/telemetry/providers/otlp/metrics.go‎

Lines changed: 6 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -27,8 +27,13 @@ func NewMetricReader(ctx context.Context, config Config) (sdkmetric.Reader, erro
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}
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func createMetricExporter(ctx context.Context, config Config) (sdkmetric.Exporter, error) {
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host, basePath := splitEndpointPath(config.Endpoint)
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opts := []otlpmetrichttp.Option{
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otlpmetrichttp.WithEndpoint(config.Endpoint),
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otlpmetrichttp.WithEndpoint(host),
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}
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if basePath != "" {
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opts = append(opts, otlpmetrichttp.WithURLPath(basePath+otlpMetricsPath))
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}
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if len(config.Headers) > 0 {

‎pkg/telemetry/providers/otlp/metrics_test.go‎

Lines changed: 23 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -16,6 +16,7 @@ func TestCreateMetricExporter(t *testing.T) {
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tests := []struct {
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name string
1818
config Config
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ctx func() context.Context
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wantErr bool
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errMsg string
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}{
@@ -26,6 +27,7 @@ func TestCreateMetricExporter(t *testing.T) {
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Headers: map[string]string{"x-api-key": "secret"},
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Insecure: true,
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},
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ctx: func() context.Context { return context.Background() },
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wantErr: false,
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},
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{
@@ -34,24 +36,37 @@ func TestCreateMetricExporter(t *testing.T) {
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Endpoint: "localhost:4318",
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Insecure: false,
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},
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ctx: func() context.Context { return context.Background() },
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wantErr: false,
3841
},
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{
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name: "error creating metrics exporter due to malformed endpoint",
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name: "endpoint with custom path",
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config: Config{
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Endpoint: "malformed//:4318",
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Endpoint: "cloud.langfuse.com/api/public/otel",
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Headers: map[string]string{"Authorization": "Basic abc123"},
4347
Insecure: false,
4448
},
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ctx: func() context.Context { return context.Background() },
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wantErr: false,
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},
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{
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name: "error creating metrics exporter due to invalid CA cert",
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config: Config{
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Endpoint: "localhost:4318",
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Insecure: false,
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CACertPath: "/nonexistent/ca.crt",
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},
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ctx: func() context.Context { return context.Background() },
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wantErr: true,
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errMsg: "invalid URL escape",
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errMsg: "failed to configure TLS for metric exporter",
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},
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}
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for _, tt := range tests {
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t.Run(tt.name, func(t *testing.T) {
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t.Parallel()
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ctx := context.Background()
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ctx := tt.ctx()
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exporter, err := createMetricExporter(ctx, tt.config)
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if tt.wantErr {
@@ -109,17 +124,13 @@ func TestNewMetricReader(t *testing.T) {
109124
wantErr: false,
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},
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{
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name: "expect error creating metrics exporter due to malformed endpoint",
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name: "endpoint with custom path",
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config: Config{
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Endpoint: "malformed//:4318",
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Headers: map[string]string{
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"x-api-key": "secret",
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"x-env": "production",
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},
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Endpoint: "cloud.langfuse.com/api/public/otel",
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Headers: map[string]string{"Authorization": "Basic abc123"},
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Insecure: false,
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},
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wantErr: true,
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errMsg: "invalid URL escape",
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wantErr: false,
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},
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}
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‎pkg/telemetry/providers/otlp/tracing.go‎

Lines changed: 6 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -15,8 +15,13 @@ import (
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)
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1717
func createTraceExporter(ctx context.Context, config Config) (sdktrace.SpanExporter, error) {
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host, basePath := splitEndpointPath(config.Endpoint)
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opts := []otlptracehttp.Option{
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otlptracehttp.WithEndpoint(config.Endpoint),
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otlptracehttp.WithEndpoint(host),
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}
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if basePath != "" {
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opts = append(opts, otlptracehttp.WithURLPath(basePath+otlpTracesPath))
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}
2126

2227
if len(config.Headers) > 0 {

‎pkg/telemetry/providers/otlp/tracing_test.go‎

Lines changed: 10 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -55,6 +55,16 @@ func TestCreateTraceExporter(t *testing.T) {
5555
ctx: func() context.Context { return context.Background() },
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wantErr: false,
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},
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{
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name: "endpoint with custom path",
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config: Config{
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Endpoint: "cloud.langfuse.com/api/public/otel",
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Headers: map[string]string{"Authorization": "Basic abc123"},
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Insecure: false,
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},
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ctx: func() context.Context { return context.Background() },
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wantErr: false,
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},
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{
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name: "error creating sdk-span-exporter due to error (cancelled context)",
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config: Config{

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