observability

[pan93412]

• chore: upgrade dependencies
• chore: update nix lockfile
• feat: implement OpenTelemetry and Prometheus basic infra
• feat: implement otelgqlgen
• feat: add slog-gin and trace ID header
• docs: add OpenTelemetry and Prometheus instruction
• feat: inject trace_id to GraphQL error
• feat: add otelpgx
• feat: add rueidisotel
• feat(graph): implement OpenTelemetry tracing for GraphQL resolvers
• feat(httpapi): implement OpenTelemetry tracing for HTTP APIs
• feat(auth): implement OpenTelemetry tracing for auth service
• feat(backend): setup otel sdk
• feat(events): implement OpenTelemetry tracing for events service
• feat(ranking): implement OpenTelemetry tracing for ranking service
• feat(sqlrunner): implement OpenTelemetry tracing for sqlrunner service
• feat(submission): implement OpenTelemetry tracing for submission service
• feat(useraccount): implement OpenTelemetry tracing for useraccount service
• chore: tidy up imports
• test(auth): handle OpenTelemetry wrapped case

[Copilot]

Pull request overview

This PR implements comprehensive OpenTelemetry and Prometheus observability infrastructure across the entire backend application, adding distributed tracing, logging, and metrics capabilities.

Key Changes

• Added OpenTelemetry SDK setup with support for multiple exporters (console, OTLP) for traces and logs
• Instrumented all service layers with tracing spans including useraccount, submission, sqlrunner, ranking, events, and auth services
• Implemented automatic tracing for HTTP APIs, GraphQL resolvers, and database operations (pgx, Redis)
• Integrated Prometheus metrics endpoint at /metrics with Gin middleware instrumentation

Reviewed changes

Copilot reviewed 33 out of 35 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
internal/otelprovider/otelprovider.go	New OpenTelemetry SDK provider with configurable exporters for traces and logs
internal/useraccount/*.go	Added tracing spans for token operations, user registration, and verification
internal/submission/submission.go	Instrumented answer submission and execution with detailed span events
internal/sqlrunner/sqlrunner.go	Added HTTP client tracing and database query instrumentation
internal/ranking/ranking.go	Implemented tracing for ranking calculations and database queries
internal/events/*.go	Added comprehensive tracing for event handling and points granting logic
internal/auth/*.go	Instrumented authentication middleware and Redis storage operations
httpapi/auth/*.go	Added OAuth 2.0 flow tracing with PKCE validation spans
graph/*.resolvers.go	Instrumented all GraphQL resolvers with tracing spans
internal/deps/deps.go	Updated to use otelpgx and rueidisotel for database/Redis tracing
cmd/backend/dependencies.go	Integrated OTel SDK lifecycle, Prometheus metrics, and trace ID headers
docs/config.md	Added comprehensive OpenTelemetry configuration documentation

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