## Summary
Implements the TODO in `evaluation_service.py`: **Track token usage** in
evaluation results.
## Changes
- **Import** `num_tokens_from_string` from `common.token_utils`
- **Prompt tokens**: Use the full prompt returned by `async_chat` when
available (includes system prompt + knowledge base + query), otherwise
fall back to the question token count
- **Completion tokens**: Count tokens in the generated answer
- **Storage**: Store `token_usage` as `{prompt_tokens,
completion_tokens, total_tokens}` in each `EvaluationResult` instead of
`None`
## Why
The evaluation pipeline previously saved `token_usage: None` for every
result. This change allows downstream consumers (e.g. evaluation
dashboards, cost tracking) to see approximate token usage per test case
using the same tokenizer (tiktoken cl100k_base) used elsewhere in
RAGFlow.
## Testing
- No new tests added; existing evaluation flow unchanged
- Token counting uses existing `num_tokens_from_string` utility
---------
Co-authored-by: kiannidev <kiannidev@users.noreply.github.com>
### What problem does this PR solve?
Cleanup synchronous functions in chat_model and implement
synchronization for conversation and dialog chats.
### Type of change
- [x] Refactoring
- [x] Performance Improvement
### What problem does this PR solve?
Feature: This PR implements a comprehensive RAG evaluation framework to
address issue #11656.
**Problem**: Developers using RAGFlow lack systematic ways to measure
RAG accuracy and quality. They cannot objectively answer:
1. Are RAG results truly accurate?
2. How should configurations be adjusted to improve quality?
3. How to maintain and improve RAG performance over time?
**Solution**: This PR adds a complete evaluation system with:
- **Dataset & test case management** - Create ground truth datasets with
questions and expected answers
- **Automated evaluation** - Run RAG pipeline on test cases and compute
metrics
- **Comprehensive metrics** - Precision, recall, F1 score, MRR, hit rate
for retrieval quality
- **Smart recommendations** - Analyze results and suggest specific
configuration improvements (e.g., "increase top_k", "enable reranking")
- **20+ REST API endpoints** - Full CRUD operations for datasets, test
cases, and evaluation runs
**Impact**: Enables developers to objectively measure RAG quality,
identify issues, and systematically improve their RAG systems through
data-driven configuration tuning.
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
