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OpenAI RAG Integration

This guide demonstrates how to use OpenAI's File Store and Vector Store APIs for RAG (Retrieval-Augmented Generation) in Semantic Router, following the OpenAI Responses API cookbook.

Overview​

The OpenAI RAG backend integrates with OpenAI's File Store and Vector Store APIs to provide a first-class RAG experience. It supports two workflow modes:

  1. Direct Search Mode (default): Synchronous retrieval using vector store search API
  2. Tool-Based Mode: Adds file_search tool to request (Responses API workflow)

Architecture​

┌─────────────┐
│   Client    │
└──────┬──────┘
       │
       ▼
┌─────────────────────────────────────┐
│     Semantic Router                 │
│  ┌───────────────────────────────┐  │
│  │      RAG Plugin               │  │
│  │  ┌─────────────────────────┐  │  │
│  │  │  OpenAI RAG Backend     │  │  │
│  │  └──────┬──────────────────┘  │  │
│  └─────────┼──────────────────── ┘  │
└────────────┼─────────────────────── ┘
             │
             ▼
┌─────────────────────────────────────┐
│      OpenAI API                     │
│  ┌──────────────┐  ┌──────────────┐ │
│  │ File Store   │  │Vector Store  │ │
│  │   API        │  │   API        │ │
│  └──────────────┘  └──────────────┘ │
└─────────────────────────────────────┘

Prerequisites​

  1. OpenAI API key with access to File Store and Vector Store APIs
  2. Files uploaded to OpenAI File Store
  3. Vector store created and populated with files

Configuration​

Basic Configuration​

Add the OpenAI RAG backend to your decision configuration:

decisions:
  - name: rag-openai-decision
    signals:
      - type: keyword
        keywords: ["research", "document", "knowledge"]
    plugins:
      rag:
        enabled: true
        backend: "openai"
        backend_config:
          vector_store_id: "vs_abc123"  # Your vector store ID
          api_key: "${OPENAI_API_KEY}"  # Or use environment variable
          max_num_results: 10
          workflow_mode: "direct_search"  # or "tool_based"

Advanced Configuration​

rag:
  enabled: true
  backend: "openai"
  similarity_threshold: 0.7
  top_k: 10
  max_context_length: 5000
  injection_mode: "tool_role"  # or "system_prompt"
  on_failure: "skip"  # or "warn" or "block"
  cache_results: true
  cache_ttl_seconds: 3600
  backend_config:
    vector_store_id: "vs_abc123"
    api_key: "${OPENAI_API_KEY}"
    base_url: "https://api.openai.com/v1"  # Optional, defaults to OpenAI
    max_num_results: 10
    file_ids:  # Optional: restrict search to specific files
      - "file-123"
      - "file-456"
    filter:  # Optional: metadata filter
      category: "research"
      published_date: "2024-01-01"
    workflow_mode: "direct_search"  # or "tool_based"
    timeout_seconds: 30

Workflow Modes​

1. Direct Search Mode (Default)​

Synchronous retrieval using vector store search API. Context is retrieved before sending the request to the LLM.

Use Case: When you need immediate context injection and want to control the retrieval process.

Example:

backend_config:
  workflow_mode: "direct_search"
  vector_store_id: "vs_abc123"

Flow:

  1. User sends query
  2. RAG plugin calls vector store search API
  3. Retrieved context is injected into request
  4. Request sent to LLM with context

2. Tool-Based Mode (Responses API)​

Adds file_search tool to the request. The LLM calls the tool automatically, and results appear in response annotations.

Use Case: When using Responses API and want the LLM to control when to search.

Example:

backend_config:
  workflow_mode: "tool_based"
  vector_store_id: "vs_abc123"

Flow:

  1. User sends query
  2. RAG plugin adds file_search tool to request
  3. Request sent to LLM
  4. LLM calls file_search tool
  5. Results appear in response annotations

Usage Examples​

Example 1: Basic RAG Query​

curl -X POST http://localhost:8080/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "X-VSR-Selected-Decision: rag-openai-decision" \
  -d '{
    "model": "gpt-4o-mini",
    "messages": [
      {
        "role": "user",
        "content": "What is Deep Research?"
      }
    ]
  }'

Example 2: Responses API with file_search Tool​

curl -X POST http://localhost:8080/v1/responses \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-4o-mini",
    "input": "What is Deep Research?",
    "tools": [
      {
        "type": "file_search",
        "file_search": {
          "vector_store_ids": ["vs_abc123"],
          "max_num_results": 5
        }
      }
    ]
  }'

Example 3: Python Client​

import requests

# Direct search mode
response = requests.post(
    "http://localhost:8080/v1/chat/completions",
    headers={
        "Content-Type": "application/json",
        "X-VSR-Selected-Decision": "rag-openai-decision"
    },
    json={
        "model": "gpt-4o-mini",
        "messages": [
            {"role": "user", "content": "What is Deep Research?"}
        ]
    }
)

result = response.json()
print(result["choices"][0]["message"]["content"])

File Store Operations​

The OpenAI RAG backend includes a File Store client for managing files:

Upload File​

import "github.com/vllm-project/semantic-router/src/semantic-router/pkg/openai"

client := openai.NewFileStoreClient("https://api.openai.com/v1", apiKey)
file, err := client.UploadFile(ctx, fileReader, "document.pdf", "assistants")

Create Vector Store​

vectorStoreClient := openai.NewVectorStoreClient("https://api.openai.com/v1", apiKey)
store, err := vectorStoreClient.CreateVectorStore(ctx, &openai.CreateVectorStoreRequest{
    Name:    "my-vector-store",
    FileIDs: []string{"file-123", "file-456"},
})

Attach File to Vector Store​

_, err := vectorStoreClient.CreateVectorStoreFile(ctx, "vs_abc123", "file-123")

Testing​

Unit Tests​

Run unit tests for OpenAI RAG:

cd src/semantic-router
go test ./pkg/openai/... -v
go test ./pkg/extproc/req_filter_rag_openai_test.go -v

E2E Tests​

Run E2E tests based on the OpenAI cookbook:

# Python-based E2E test
python e2e/testing/08-rag-openai-test.py --base-url http://localhost:8080

# Go-based E2E test (requires Kubernetes cluster)
make e2e-test E2E_TESTS=rag-openai

OpenAI API Validation Test Suite​

Validation tests ensure the OpenAI API implementation (Files, Vector Stores, Search) stays compatible with upstream. Adapted from openai-python/tests. Run when OPENAI_API_KEY is set.

Python E2E (contract validation against real API):

# From repo root; skips all tests if OPENAI_API_KEY is not set
OPENAI_API_KEY=sk-... python e2e/testing/09-openai-api-validation-test.py --verbose

# Optional: override API base URL
OPENAI_BASE_URL=https://api.openai.com/v1 OPENAI_API_KEY=sk-... python e2e/testing/09-openai-api-validation-test.py

Go integration (pkg/openai client against real API):

cd src/semantic-router
# Skips tests if OPENAI_API_KEY is not set
OPENAI_API_KEY=sk-... go test -tags=openai_validation ./pkg/openai -v

Tests cover: Files (list, upload, get, delete), Vector Stores (list, create, get, update, delete), Vector Store Files (list), and Vector Store Search (response schema).

Monitoring and Observability​

The OpenAI RAG backend exposes the following metrics:

  • rag_retrieval_attempts_total{backend="openai", decision="...", status="success|error"}
  • rag_retrieval_latency_seconds{backend="openai", decision="..."}
  • rag_similarity_score{backend="openai", decision="..."}
  • rag_context_length_chars{backend="openai", decision="..."}
  • rag_cache_hits_total{backend="openai"}
  • rag_cache_misses_total{backend="openai"}

Tracing​

OpenTelemetry spans are created for:

  • semantic_router.rag.retrieval - RAG retrieval operation
  • semantic_router.rag.context_injection - Context injection operation

Error Handling​

The RAG plugin supports three failure modes:

  • skip (default): Continue without context, log warning
  • warn: Continue with warning header
  • block: Return error response (503)
rag:
  on_failure: "skip"  # or "warn" or "block"

Best Practices​

  1. Use Direct Search for Synchronous Workflows: When you need immediate context injection
  2. Use Tool-Based for Responses API: When using Responses API and want LLM-controlled search
  3. Cache Results: Enable caching for frequently accessed queries
  4. Set Appropriate Timeouts: Configure timeout_seconds based on your vector store size
  5. Filter Results: Use file_ids or filter to narrow search scope
  6. Monitor Metrics: Track retrieval latency and similarity scores

Troubleshooting​

No Results Found​

  • Verify vector store ID is correct
  • Check that files are attached to the vector store
  • Ensure files have completed processing (check file_counts.completed)

High Latency​

  • Reduce max_num_results
  • Enable result caching
  • Use file_ids to limit search scope

Authentication Errors​

  • Verify API key is correct
  • Check API key has access to File Store and Vector Store APIs
  • Ensure base URL is correct (if using custom endpoint)

References​