rustfs/crates/config/README.md

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# RustFS Config - Configuration Management

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  <strong>Configuration management and validation module for RustFS distributed object storage</strong>
</p>

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---

## 📖 Overview

**RustFS Config** provides configuration management and validation capabilities for the [RustFS](https://rustfs.com) distributed object storage system. For the complete RustFS experience, please visit the [main RustFS repository](https://github.com/rustfs/rustfs).

## ✨ Features

- Multi-format configuration support (TOML, YAML, JSON, ENV)
- Environment variable integration and override
- Configuration validation and type safety
- Hot-reload capabilities for dynamic updates
- Default value management and fallbacks
- Secure credential handling and encryption

## 📚 Documentation

For comprehensive documentation, examples, and usage guides, please visit the main [RustFS repository](https://github.com/rustfs/rustfs).

## Environment Variable Naming Conventions

RustFS uses a flat naming style for top-level configuration: environment variables are `RUSTFS_*` without nested module segments.

Examples:
- `RUSTFS_REGION`
- `RUSTFS_ADDRESS`
- `RUSTFS_VOLUMES`
- `RUSTFS_LICENSE`
- `RUSTFS_LICENSE_PUBLIC_KEY`

Current guidance:
- Prefer module-specific names only when they are not top-level product configuration.
- Renamed variables must keep backward-compatible aliases until before beta.
- Alias usage must emit deprecation warnings and be treated as transitional only.
- Deprecated example:
  - `RUSTFS_ENABLE_SCANNER` -> `RUSTFS_SCANNER_ENABLED`
  - `RUSTFS_ENABLE_HEAL` -> `RUSTFS_HEAL_ENABLED`
  - `RUSTFS_DATA_SCANNER_START_DELAY_SECS` -> `RUSTFS_SCANNER_START_DELAY_SECS`

## License environment variables

- `RUSTFS_LICENSE` contains the signed license token.
- `RUSTFS_LICENSE_PUBLIC_KEY` contains the RSA public key used to verify signed license tokens.

## CORS environment variables

- `RUSTFS_CORS_ALLOWED_ORIGINS` defaults to empty, so the S3 endpoint emits no generic CORS headers unless configured. Set `*` for wildcard origins without credentials, or a comma-separated allow-list for credentialed explicit origins.
- `RUSTFS_CONSOLE_CORS_ALLOWED_ORIGINS` defaults to `*` for the console service.

## Browser redirect environment variables

- `RUSTFS_BROWSER_REDIRECT_URL` sets the externally reachable browser origin used for OIDC callback, console success redirect, and logout fallback URLs. Configure it to the public scheme and authority without a path, for example `https://console.example.com`. In load-balancer deployments, keep OIDC authorize and callback requests on the same backend node because the in-flight OIDC `state` is local to the RustFS node.

## Distributed endpoint locality

- `RUSTFS_LOCAL_ENDPOINT_HOST` identifies this server's host in a distributed `RUSTFS_VOLUMES` topology without resolving every peer during startup. Set it to exactly one host, without a scheme, port, or path. It is accepted only for orchestrated URL topologies and must match at least one endpoint on the RustFS server port; invalid or unmatched values fail startup. Leave it unset to retain DNS-based locality discovery.

## Scanner environment aliases

- `RUSTFS_SCANNER_SPEED` (canonical, also accepts `MINIO_SCANNER_SPEED`)
- `RUSTFS_SCANNER_DELAY` (canonical)
- `RUSTFS_SCANNER_MAX_WAIT_SECS` (canonical)
- `RUSTFS_SCANNER_CYCLE` (canonical, also accepts `MINIO_SCANNER_CYCLE`)
- `RUSTFS_SCANNER_START_DELAY_SECS` (canonical)
- `RUSTFS_DATA_SCANNER_START_DELAY_SECS` (deprecated alias for compatibility)
- `RUSTFS_SCANNER_IDLE_MODE` (canonical)
- `RUSTFS_SCANNER_CACHE_SAVE_TIMEOUT_SECS` (canonical)
- `RUSTFS_SCANNER_CYCLE_MAX_DURATION_SECS` (canonical)
- `RUSTFS_SCANNER_CYCLE_MAX_OBJECTS` (canonical)
- `RUSTFS_SCANNER_CYCLE_MAX_DIRECTORIES` (canonical)

Scanner cycle budget controls:

- When `RUSTFS_SCANNER_CYCLE_MAX_DURATION_SECS` is unset, the finite default is 1800 seconds (30 minutes), matching the scanner benchmark guidance.
- An explicit `0` preserves the compatibility behavior of an unbounded runtime budget. Object and directory budgets likewise remain unbounded when explicitly set to `0`.
- A timed-out cycle cancels cooperative scanner work, then fences its leader epoch before releasing the lease. An uncooperative I/O operation is dropped after the bounded shutdown window; its cursor is not claimed to be durable and the scanner reports `recovery-required` when the worker cannot stop cooperatively, the cycle state was not confirmed durable, or epoch fencing cannot be persisted.

## Mmap read environment aliases

- `RUSTFS_OBJECT_MMAP_READ_ENABLE` (canonical)
- `RUSTFS_OBJECT_ZERO_COPY_ENABLE` (deprecated alias for compatibility)

## Health compatibility switches

- `RUSTFS_HEALTH_ENDPOINT_ENABLE`
  - controls canonical `/health`, `/health/live`, and `/health/ready` endpoint exposure.
- `RUSTFS_HEALTH_MINIMAL_RESPONSE_ENABLE`
  - enables minimal payload mode for GET health responses (`status`, `ready` only).
- `RUSTFS_HEALTH_READINESS_CACHE_TTL_MS`
  - TTL for readiness cache evaluation.
- `RUSTFS_HEALTH_OBJECT_PROGRESS_ENABLE`
  - withdraws readiness when bounded object read/write stages stop completing while requests remain active.
  - default is `true`.
- `RUSTFS_HEALTH_OBJECT_PROGRESS_TIMEOUT_MS`
  - maximum time without completion in a bounded object stage before readiness is withdrawn.
  - default is `30000`; `0` uses the default.
  - the effective value is at least 5 seconds longer than `RUSTFS_OBJECT_LOCK_ACQUIRE_TIMEOUT`.
  - this readiness SLO is independent of disk read/write failure deadlines and may withdraw traffic before those deadlines expire.
- `RUSTFS_HEALTH_COMPAT_BUSY_CHECK_ENABLE`
  - enables busy protection behavior for health probes.
  - default is `false`.
- `RUSTFS_HEALTH_COMPAT_BUSY_MAX_ACTIVE_REQUESTS`
  - max active HTTP requests; health probes return `429` when active requests reach or exceed this value.
  - `0` disables thresholding even if busy protection is enabled.
- `RUSTFS_HEALTH_COMPAT_KMS_READY_CHECK_ENABLE`
  - enables KMS readiness enforcement for `/health/ready`.
  - default is `false`.

## Object lock admission environment variables

- `RUSTFS_PUT_COMMIT_NAMESPACE_LOCK_ACQUIRE_TIMEOUT_MS`
  - experimental same-object PUT commit namespace-lock admission budget.
  - default is `0`, which disables this override and keeps `RUSTFS_OBJECT_LOCK_ACQUIRE_TIMEOUT` behavior.
  - when set, only `put_object_commit` write-lock acquisition is bounded by this millisecond budget; other namespace lock users keep the global object-lock timeout.
  - timeout returns S3 `SlowDown`, so clients should use normal SDK retry handling.
  - this is not a fdatasync or group-commit switch. Track fdatasync batching separately with `rustfs_s3_put_object_rename_fdatasync_batch_files`.

## Foreground write admission environment variables

Large direct `PutObject` requests and multipart `UploadPart` requests share one
per-process permit pool that bounds how many bodies are ingested and written
concurrently. Small direct PUTs stay on the legacy path.

- `RUSTFS_PUT_LARGE_FOREGROUND_ADMISSION_ENABLE`
  - enables the default-on pool; `false` keeps only the soft request counter.
  - default is `true`.
- `RUSTFS_PUT_LARGE_FOREGROUND_ADMISSION_LIMIT`
  - permits in the pool; `0` derives half of `RUSTFS_OBJECT_MAX_CONCURRENT_DISK_READS`, clamped to `32`.
  - default is `0` (32 permits at stock settings).
- `RUSTFS_PUT_LARGE_FOREGROUND_ADMISSION_MIN_SIZE_BYTES`
  - smallest direct `PutObject` that takes a permit; unknown-size requests always do.
  - default is `33554432` (32 MiB).
- `RUSTFS_PUT_LARGE_FOREGROUND_ADMISSION_WAIT_TIMEOUT_MS`
  - how long a direct `PutObject` waits for a permit before returning S3 `SlowDown`.
  - default is `250`.
- `RUSTFS_PUT_MULTIPART_FOREGROUND_ADMISSION_MIN_SIZE_BYTES`
  - smallest `UploadPart` that takes a permit; `0` gates every part.
  - default is `0`.
- `RUSTFS_PUT_MULTIPART_FOREGROUND_ADMISSION_WAIT_TIMEOUT_MS`
  - how long an `UploadPart` waits in the bounded queue for a permit before returning S3 `SlowDown`; `0` rejects immediately when the pool is full.
  - default is `10000`. Parts wait before body ingest, so SDK-default clients that send every part of an upload concurrently drain through the pool instead of failing on a full pool.
  - RustFS does not read the request body while a part is queued, so the client's socket write stalls for the whole wait and whatever timeout the client or an intermediary has configured competes with this value. Keep it with margin below the shortest such timeout in use (botocore applies its 60 s `connect_timeout` to the body write; the AWS SDK for Java v2 has a 30 s socket write timeout; reverse proxies add their own body timeouts); a wait that outlives the client timeout surfaces as a dropped connection instead of `SlowDown`.
- `RUSTFS_PUT_MULTIPART_FOREGROUND_ADMISSION_MAX_PENDING`
  - maximum `UploadPart` requests waiting for a permit at once; parts beyond it return `SlowDown` without waiting.
  - default is `0`, which derives 16 times the permit limit (512 at stock settings).
  - each queued HTTP/1 part holds whatever unread body the client already pushed into the connection's kernel receive buffer (an HTTP/2 part holds up to its flow-control window in process memory), so this depth also bounds that memory. RustFS leaves the receive buffer to kernel autotuning (see `RUSTFS_HTTP_SOCKET_RECV_BUFFER_BYTES` below), which keeps an unread connection at the kernel's initial size (128 KiB on current Linux).
- `RUSTFS_PUT_FOREGROUND_ADMISSION_ENABLE`, `RUSTFS_PUT_FOREGROUND_ADMISSION_LIMIT`, `RUSTFS_PUT_FOREGROUND_ADMISSION_WAIT_TIMEOUT_MS`
  - experimental strict gate that applies to every foreground write regardless of size and replaces the pool above when enabled.
  - default is disabled; enabling it with limit `0` disables foreground write admission entirely.

## HTTP listener socket environment variables

- `RUSTFS_HTTP_SOCKET_RECV_BUFFER_BYTES`
  - fixed `SO_RCVBUF` for the API listener, inherited by every accepted socket; `0` leaves the receive buffer to kernel autotuning.
  - default is `0`. Earlier releases hard-coded 4 MiB, which Linux doubles to 8 MiB and which disables autotuning, so every connection whose body was not being read yet (a multipart part queued for a foreground write permit) could accumulate up to 8 MiB of unread body in kernel memory; at SDK-default multipart concurrency that was enough to push a node into TCP memory pressure.
  - with autotuning the per-connection receive ceiling is the kernel's (`net.ipv4.tcp_rmem` max, 6 MiB on stock Linux) instead of the former fixed 8 MiB, so a single very high-bandwidth-delay connection may see a somewhat lower ceiling; raise `net.ipv4.tcp_rmem` first, and set this variable only on kernels without receive-buffer autotuning (illumos/Solaris) or where the sysctl cannot be changed.
  - the send buffer stays fixed at 4 MiB because the stock Linux send autotuning ceiling (`net.ipv4.tcp_wmem` max, 4 MiB) is lower than a GB-level response stream needs.

## Remote tier timeout environment variables

- `RUSTFS_TIER_REMOTE_CONNECT_TIMEOUT_SECS`
  - remote tier TCP connect timeout.
  - default is `10`.
  - must be positive; zero fails tier client initialization, while an invalid integer is logged and falls back to the default.
- `RUSTFS_TIER_REMOTE_REQUEST_TIMEOUT_SECS`
  - remote tier request timeout through response headers.
  - default is `86400` so large transition uploads keep a production-safe budget.
  - must be positive; zero fails tier client initialization, while an invalid integer is logged and falls back to the default. Very large values are accepted and act as a correspondingly long budget.
- `RUSTFS_TIER_REMOTE_RESPONSE_BODY_IDLE_TIMEOUT_SECS`
  - maximum idle time between remote tier response-body chunks.
  - default is `60`; the timer resets only when non-empty body data keeps progressing.
  - must be positive; zero fails tier client initialization, while an invalid integer is logged and falls back to the default.

## Drive timeout environment variables

- `RUSTFS_DRIVE_METADATA_TIMEOUT_SECS`
- `RUSTFS_DRIVE_DISK_INFO_TIMEOUT_SECS`
- `RUSTFS_DRIVE_LIST_DIR_TIMEOUT_SECS`
- `RUSTFS_DRIVE_WALKDIR_TIMEOUT_SECS`
- `RUSTFS_DRIVE_WALKDIR_STALL_TIMEOUT_SECS`

Legacy compatibility fallback:
- `RUSTFS_DRIVE_MAX_TIMEOUT_DURATION`
  This legacy variable is treated as a deprecated fallback for the operation-specific drive timeout variables above when a canonical variable is unset.

Drive timeout health-action policy:
- `RUSTFS_DRIVE_TIMEOUT_HEALTH_ACTION`
  - `mark_failure` (default): timeout marks failure and may transition drive runtime state.
  - `ignore_scanner`: timeout does not mark failure for scanner-sensitive operations (`walk_dir`, `read_metadata`, `list_dir`, `disk_info`).

Drive timeout profile preset:
- `RUSTFS_DRIVE_TIMEOUT_PROFILE`
  - `default` (default): keep current timeout defaults.
  - `high_latency`: use 60s default timeout for scanner-sensitive operations when no operation-specific override is set (`read_metadata`, `disk_info`, `list_dir`, `walk_dir`, `walk_dir_stall`, and object-capacity scan base/maximum budgets).
- Precedence:
  - Explicit per-operation timeout env (`RUSTFS_DRIVE_*_TIMEOUT_SECS`) takes highest precedence.
  - Explicit object-capacity timeout env (`RUSTFS_CAPACITY_STAT_TIMEOUT`, `RUSTFS_CAPACITY_MAX_TIMEOUT`) takes precedence for capacity scans.
  - Then `RUSTFS_DRIVE_MAX_TIMEOUT_DURATION` legacy fallback.
  - Then the profile-derived default (`default` or `high_latency`).

## Admin peer probe timeout

- `RUSTFS_ADMIN_PEER_PROBE_TIMEOUT_SECS`
  - total per-peer budget for the `server_info`/`storage_info` admin probe round; `server_info` may reconnect once and `storage_info` remains a single attempt.
  - default is `10` seconds, preserving the previous two-attempt worst-case budget.
  - values must be positive; `0` or an invalid value falls back to the default, and values above `60` are clamped to `60`.
  - the setting is read by the aggregating node only; it does not change the internode RPC wire contract. Any retry shares one round deadline rather than receiving a fresh timeout.

## Startup filesystem boundary policy

- `RUSTFS_UNSUPPORTED_FS_POLICY` controls startup behavior when RustFS detects local endpoint filesystems that are outside the supported production boundary.
  - `warn` (default): log warning and continue startup.
  - `fail`: abort startup with an error.

RustFS production guidance remains direct-attached local POSIX filesystems. Network-mounted filesystems (for example `nfs`, `cifs`, `smb2`, and `fuse.*`) are treated as unsupported by this startup guard.

## 📄 License

This project is licensed under the Apache License 2.0 - see the [LICENSE](../../LICENSE) file for details.