> ## Documentation Index > Fetch the complete documentation index at: https://onr.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. # Access Log Fields > All supported variables for logging.access_log_format. ONR access logs support an nginx-like format string via `logging.access_log_format` (or `logging.access_log_format_preset`). ## Formatting rules * Variables are referenced as `$name` (example: `$status`). * If a variable is missing or empty, ONR prints `-` at that position. * `$$` renders a literal `$`. ## Configuration In `onr.yaml`: ```yaml theme={null} logging: access_log: true access_log_path: "" # empty = stdout access_log_format: "" # non-empty overrides preset access_log_format_preset: "" # onr_combined | onr_minimal access_log_rotate: enabled: false max_size_mb: 100 max_backups: 14 max_age_days: 14 compress: false ``` Rotation notes: * Rotation only applies when `access_log_path` is non-empty (file output). * When `access_log_rotate.enabled=true`, `access_log_path` is required. * Rotation triggers on either day boundary (local time) or size threshold. * Archive file pattern: `.YYYYMMDD-HHMMSS.NNNNNNNNN` (or `.gz` when `compress=true`). Rotation knobs: * `max_size_mb`: rotate when the next write would exceed this file size. * `max_backups`: keep only the newest N archives. * `max_age_days`: remove archives older than N days; `0` disables age-based cleanup. * `compress`: gzip archive files after rotation. Daily-first setup example: ```yaml theme={null} logging: access_log: true access_log_path: "./logs/access.log" access_log_rotate: enabled: true max_size_mb: 102400 # keep very large if you want day-boundary rotation to dominate max_backups: 14 max_age_days: 14 compress: false ``` Note: * Current behavior is `day-boundary OR size-threshold` (not an exclusive mode switch). ## Field reference **Request line fields** | Variable | Meaning | | ------------- | ------------------------------------------------------------------------------------------------- | | `$time_local` | Timestamp formatted as `YYYY/MM/DD - HH:MM:SS`. | | `$status` | Downstream HTTP status code returned to the client. | | `$latency` | End-to-end request latency as a Go duration string (example: `123ms`, `1.2s`). | | `$latency_ms` | End-to-end request latency in milliseconds. If proxy result latency is available, ONR may use it. | | `$client_ip` | Client IP as seen by the server. | | `$method` | Downstream HTTP method (example: `GET`, `POST`). | | `$path` | Downstream request path (URL path only, without query string). | **Identity and routing** | Variable | Meaning | | ------------------ | ----------------------------------------------------------------------------------------------------------- | | `$request_id` | Request ID used for tracing. | | `$appname` | Client app name for observability. Resolved from `appname` header or (optional) inferred from `User-Agent`. | | `$provider` | Selected provider name (from DSL selection and routing). | | `$provider_source` | Provider selection source (for example: forced header vs models routing). | | `$api` | Normalized API category (example: `chat.completions`). | | `$stream` | Whether the request is treated as streaming (`true`/`false`) when available. | | `$model` | Requested/selected model. | **Usage and cost** | Variable | Meaning | | ------------------------ | -------------------------------------------------------------------------------------- | | `$usage_stage` | Where usage data comes from (for example upstream-provided vs best-effort estimation). | | `$input_tokens` | Input tokens. | | `$output_tokens` | Output tokens. | | `$total_tokens` | Total tokens. | | `$cache_read_tokens` | Cache read tokens (when available). | | `$cache_write_tokens` | Cache write tokens (when available). | | `$cost_total` | Total cost. | | `$cost_input` | Input cost. | | `$cost_output` | Output cost. | | `$cost_cache_read` | Cache read cost (when available). | | `$cost_cache_write` | Cache write cost (when available). | | `$billable_input_tokens` | Billable input tokens (after provider-specific adjustments). | | `$cost_multiplier` | Effective multiplier applied to pricing (if configured). | | `$cost_model` | Pricing model used for cost calculation. | | `$cost_channel` | Channel identifier used for cost attribution (if available). | | `$cost_unit` | Cost unit (implementation-defined; depends on pricing config). | Flat usage extras: * When `usage_extract custom;` uses `usage_fact ...` with non-legacy detail, ONR also emits flattened usage fields into the access log. * These keys are appended directly as normal log variables and follow a snake\_case convention derived from `dimension + attributes + unit`. * Legacy scalar usage stays unchanged: `input_tokens`, `output_tokens`, `total_tokens`, `cache_read_tokens`, `cache_write_tokens`. * Typical examples: * `$cache_write_ttl_5m_tokens` * `$cache_write_ttl_1h_tokens` * `$server_tool_web_search_calls` * `$image_generate_images` * `$image_edit_images` * `$audio_tts_seconds` * `$audio_stt_seconds` * `$audio_translate_seconds` * For Anthropic non-stream `/v1/messages`, `cache_write token attr.ttl="5m"` and `attr.ttl="1h"` can therefore appear both as: * `$cache_write_tokens` * `$cache_write_ttl_5m_tokens` * `$cache_write_ttl_1h_tokens` * The same flattening applies to canonical image/audio/tool facts extracted by ONR or produced by API-specific OpenAI presets such as `openai_responses`, `openai_images_generations`, or `openai_audio_speech`, for example: * `image.generate image` * `image.edit image` * `audio.tts second` * `audio.stt second` * `audio.translate second` * These flattened keys are only present when the corresponding `usage_fact` matched or was produced with quantity `0` from an upstream response that included the field. **Upstream and streaming performance** | Variable | Meaning | | ------------------ | -------------------------------------------------------------- | | `$upstream_status` | Upstream HTTP status code (when an upstream request was made). | | `$finish_reason` | Normalized finish reason when extractable. | | `$ttft_ms` | Time-to-first-token in milliseconds (streaming). | | `$tps` | Tokens per second (streaming), best-effort. |