[Docs] Litellm architecture fixes 2 (#19252)

* fixes 1

* docs fix

* docs fix

* docs fix

* docs fix
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Ishaan Jaff 2026-01-16 14:52:16 -08:00 committed by GitHub
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2 changed files with 124 additions and 45 deletions

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@ -28,16 +28,25 @@ sequenceDiagram
participant Client
participant ProxyServer as proxy/proxy_server.py
participant Auth as proxy/auth/user_api_key_auth.py
participant Redis as Redis Cache
participant Hooks as proxy/hooks/
participant Router as router.py
participant Main as main.py
participant Main as main.py + utils.py
participant Handler as llms/custom_httpx/llm_http_handler.py
participant Transform as llms/{provider}/chat/transformation.py
participant Provider as LLM Provider API
participant CostCalc as cost_calculator.py
participant LoggingObj as litellm_logging.py
participant DBWriter as db/db_spend_update_writer.py
participant Postgres as PostgreSQL
%% Request Flow
Client->>ProxyServer: POST /v1/chat/completions
ProxyServer->>Auth: user_api_key_auth()
Auth->>Redis: Check API key cache
Redis-->>Auth: Key info + spend limits
ProxyServer->>Hooks: max_budget_limiter, parallel_request_limiter
Hooks->>Redis: Check/increment rate limit counters
ProxyServer->>Router: route_request()
Router->>Main: litellm.acompletion()
Main->>Handler: BaseLLMHTTPHandler.completion()
@ -45,8 +54,25 @@ sequenceDiagram
Handler->>Provider: HTTP Request
Provider-->>Handler: Response
Handler->>Transform: ProviderConfig.transform_response()
Handler-->>Hooks: async_log_success_event()
Handler-->>Client: ModelResponse
Transform-->>Handler: ModelResponse
Handler-->>Main: ModelResponse
%% Cost Attribution (in utils.py wrapper)
Main->>LoggingObj: update_response_metadata()
LoggingObj->>CostCalc: _response_cost_calculator()
CostCalc->>CostCalc: completion_cost(tokens × price)
CostCalc-->>LoggingObj: response_cost
LoggingObj-->>Main: Set response._hidden_params["response_cost"]
Main-->>ProxyServer: ModelResponse (with cost in _hidden_params)
%% Response Headers + Async Logging
ProxyServer->>ProxyServer: Extract cost from hidden_params
ProxyServer->>LoggingObj: async_success_handler()
LoggingObj->>Hooks: async_log_success_event()
Hooks->>DBWriter: update_database(response_cost)
DBWriter->>Redis: Queue spend increment
DBWriter->>Postgres: Batch write spend logs (async)
ProxyServer-->>Client: ModelResponse + x-litellm-response-cost header
```
### Proxy Components
@ -75,11 +101,19 @@ graph TD
Main["main.py"]
end
subgraph "Infrastructure"
DualCache["DualCache<br/>(in-memory + Redis)"]
Postgres["PostgreSQL<br/>(keys, teams, spend logs)"]
end
Client --> Endpoint
Endpoint --> Auth
Auth --> DualCache
DualCache -.->|cache miss| Postgres
Auth --> PreCall
PreCall --> RouteRequest
RouteRequest --> Router
Router --> DualCache
Router --> Main
Main --> Client
```
@ -119,6 +153,93 @@ graph TD
To add a new proxy hook, implement `CustomLogger` and register in `PROXY_HOOKS`.
### Infrastructure Components
The AI Gateway uses external infrastructure for persistence and caching:
```mermaid
graph LR
subgraph "AI Gateway (proxy/)"
Proxy["proxy_server.py"]
Auth["auth/user_api_key_auth.py"]
DBWriter["db/db_spend_update_writer.py<br/>DBSpendUpdateWriter"]
InternalCache["utils.py<br/>InternalUsageCache"]
CostCallback["hooks/proxy_track_cost_callback.py<br/>_ProxyDBLogger"]
Scheduler["APScheduler<br/>ProxyStartupEvent"]
end
subgraph "SDK (litellm/)"
Router["router.py<br/>Router.cache (DualCache)"]
LLMCache["caching/caching_handler.py<br/>LLMCachingHandler"]
CacheClass["caching/caching.py<br/>Cache"]
end
subgraph "Redis (caching/redis_cache.py)"
RateLimit["Rate Limit Counters"]
SpendQueue["Spend Increment Queue"]
KeyCache["API Key Cache"]
TPM_RPM["TPM/RPM Tracking"]
Cooldowns["Deployment Cooldowns"]
LLMResponseCache["LLM Response Cache"]
end
subgraph "PostgreSQL (proxy/schema.prisma)"
Keys["LiteLLM_VerificationToken"]
Teams["LiteLLM_TeamTable"]
SpendLogs["LiteLLM_SpendLogs"]
Users["LiteLLM_UserTable"]
end
Auth --> InternalCache
InternalCache --> KeyCache
InternalCache -.->|cache miss| Keys
InternalCache --> RateLimit
Router --> TPM_RPM
Router --> Cooldowns
LLMCache --> CacheClass
CacheClass --> LLMResponseCache
CostCallback --> DBWriter
DBWriter --> SpendQueue
DBWriter --> SpendLogs
Scheduler --> SpendLogs
Scheduler --> Keys
```
| Component | Purpose | Key Files/Classes |
|-----------|---------|-------------------|
| **Redis** | Rate limiting, API key caching, TPM/RPM tracking, cooldowns, LLM response caching, spend queuing | `caching/redis_cache.py` (`RedisCache`), `caching/dual_cache.py` (`DualCache`) |
| **PostgreSQL** | API keys, teams, users, spend logs | `proxy/utils.py` (`PrismaClient`), `proxy/schema.prisma` |
| **InternalUsageCache** | Proxy-level cache for rate limits + API keys (in-memory + Redis) | `proxy/utils.py` (`InternalUsageCache`) |
| **Router.cache** | TPM/RPM tracking, deployment cooldowns, client caching (in-memory + Redis) | `router.py` (`Router.cache: DualCache`) |
| **LLMCachingHandler** | SDK-level LLM response/embedding caching | `caching/caching_handler.py` (`LLMCachingHandler`), `caching/caching.py` (`Cache`) |
| **DBSpendUpdateWriter** | Batches spend updates to reduce DB writes | `proxy/db/db_spend_update_writer.py` (`DBSpendUpdateWriter`) |
| **Cost Tracking** | Calculates and logs response costs | `proxy/hooks/proxy_track_cost_callback.py` (`_ProxyDBLogger`) |
**Background Jobs** (APScheduler, initialized in `proxy/proxy_server.py``ProxyStartupEvent.initialize_scheduled_background_jobs()`):
| Job | Interval | Purpose | Key Files |
|-----|----------|---------|-----------|
| `update_spend` | 60s | Batch write spend logs to PostgreSQL | `proxy/db/db_spend_update_writer.py` |
| `reset_budget` | 10-12min | Reset budgets for keys/users/teams | `proxy/management_helpers/budget_reset_job.py` |
| `add_deployment` | 10s | Sync new model deployments from DB | `proxy/proxy_server.py` (`ProxyConfig`) |
| `cleanup_old_spend_logs` | cron/interval | Delete old spend logs | `proxy/management_helpers/spend_log_cleanup.py` |
| `check_batch_cost` | 30min | Calculate costs for batch jobs | `proxy/management_helpers/check_batch_cost_job.py` |
| `check_responses_cost` | 30min | Calculate costs for responses API | `proxy/management_helpers/check_responses_cost_job.py` |
| `process_rotations` | 1hr | Auto-rotate API keys | `proxy/management_helpers/key_rotation_manager.py` |
| `_run_background_health_check` | continuous | Health check model deployments | `proxy/proxy_server.py` |
| `send_weekly_spend_report` | weekly | Slack spend alerts | `proxy/utils.py` (`SlackAlerting`) |
| `send_monthly_spend_report` | monthly | Slack spend alerts | `proxy/utils.py` (`SlackAlerting`) |
**Cost Attribution Flow:**
1. LLM response returns to `utils.py` wrapper after `litellm.acompletion()` completes
2. `update_response_metadata()` (`llm_response_utils/response_metadata.py`) is called
3. `logging_obj._response_cost_calculator()` (`litellm_logging.py`) calculates cost via `litellm.completion_cost()` (`cost_calculator.py`)
4. Cost is stored in `response._hidden_params["response_cost"]`
5. `proxy/common_request_processing.py` extracts cost from `hidden_params` and adds to response headers (`x-litellm-response-cost`)
6. `logging_obj.async_success_handler()` triggers callbacks including `_ProxyDBLogger.async_log_success_event()`
7. `DBSpendUpdateWriter.update_database()` queues spend increments to Redis
8. Background job `update_spend` flushes queued spend to PostgreSQL every 60s
---
## 2. SDK Request Flow

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@ -10201,48 +10201,6 @@
"mode": "completion",
"output_cost_per_token": 5e-07
},
"deepseek-v3-2-251201": {
"input_cost_per_token": 0.0,
"litellm_provider": "volcengine",
"max_input_tokens": 98304,
"max_output_tokens": 32768,
"max_tokens": 32768,
"mode": "chat",
"output_cost_per_token": 0.0,
"supports_assistant_prefill": true,
"supports_function_calling": true,
"supports_prompt_caching": true,
"supports_reasoning": true,
"supports_tool_choice": true
},
"glm-4-7-251222": {
"input_cost_per_token": 0.0,
"litellm_provider": "volcengine",
"max_input_tokens": 204800,
"max_output_tokens": 131072,
"max_tokens": 131072,
"mode": "chat",
"output_cost_per_token": 0.0,
"supports_assistant_prefill": true,
"supports_function_calling": true,
"supports_prompt_caching": true,
"supports_reasoning": true,
"supports_tool_choice": true
},
"kimi-k2-thinking-251104": {
"input_cost_per_token": 0.0,
"litellm_provider": "volcengine",
"max_input_tokens": 229376,
"max_output_tokens": 32768,
"max_tokens": 32768,
"mode": "chat",
"output_cost_per_token": 0.0,
"supports_assistant_prefill": true,
"supports_function_calling": true,
"supports_prompt_caching": true,
"supports_reasoning": true,
"supports_tool_choice": true
},
"doubao-embedding": {
"input_cost_per_token": 0.0,
"litellm_provider": "volcengine",