3.0.0-beta.2

Breaking changes

If you are upgrading to this beta version, you must update your configuration files to accommodate the following syntax refactors:

• Rate limit windows - syntax updated to enforce standard duration strings (e.g., 10s, 5m, 1h).
• OTLP verification - no_verify has been renamed to no_verification and now operates strictly as a configuration flag.
• OTLP defaults - OTLP sink now uses log_style modern default, which may break existing configurations with custom OTLP log formats.
• Proxy configuration - syntax for passive/active health checks, load balancing algorithms, and connection retries has been unified into a cleaner, more consistent format.
• Incoming trace context discarded by default - Ferron no longer trusts incoming traceparent, tracestate, or baggage headers unless trust_request true is explicitly set in the trace block. Previously, incoming trace context was always parsed and used as the parent span. To restore the old behavior, add trust_request true to your http { trace { ... } } block.

Added

Modules

• http-abuseban - a new module for lightweight, native Fail2ban-like IP banning with temporary lockouts based on rate limit breaches and brute-force failures.
• http-traceid - a new module that injects the current request's trace ID into HTTP response headers (configurable header name, optional on-demand reflection via X-Ferron-Trace-Reflect).
• tls-http - support for obtaining TLS certificates from a remote HTTP endpoint, featuring automatic refresh cycles and dedicated observability metrics.
• OS metrics - added Windows support for native process metrics in the metrics-process module.

Reverse proxy & load balancing

• circuit_breaker - new directive with rolling failure windows, temporary backend ejection, and half-open recovery states.
• p2c_ewma - a new adaptive, latency-aware load balancing algorithm combining Power of Two Choices with Exponentially Weighted Moving Average (EWMA) latency scoring.
• Session affinity (sticky sessions) - native support for cookie, header, ip, and hash types utilizing a Ketama-style hash ring for deterministic backend routing.
• String interpolation - upstream URLs and Unix socket paths now support interpolated strings.
• SRV routing - added active health check support for SRV upstream URLs.
• Outbound mTLS - reverse proxy upstreams now support presenting client certificates (cert and key subdirectives) for mutual TLS authentication with HTTPS backends, including per-upstream credential scoping and SRV upstream support.

DNS & ACME

• 58 new DNS providers - native ACME DNS-01 challenge support expanded to include Alibaba Cloud DNS, Azure DNS, ClouDNS, Hetzner DNS, Oracle Cloud DNS, Vercel, Vultr, Yandex Cloud DNS, and 50+ others.
• CLI arguments in post-obtain command - added support for passing CLI arguments to the post-obtain command in automatic TLS configurations.

HTTP server core

• basic_auth_concurrency - global directive to limit concurrent, resource-heavy password verification tasks across all basic_auth blocks.
• Cache purging - native PURGE HTTP method support for targeted cache invalidation via the purge_method and purge_allowed_ips subdirectives.
• force_trace - global directive to force trace context creation for every request even when tracing is not explicitly enabled by a module, useful for debugging or log correlation.
• trust_request - new directive in the trace block to accept incoming traceparent, tracestate, and baggage headers as the parent trace context. Default: false. When disabled (default), incoming trace headers are discarded and Ferron generates a fresh trace ID for each request.
• Optimal server-preferred compression algorithm - now supports automatic detection of the optimal compression algorithm based on client preferences (GitHub issue).

Authentication

• Forwarded authentication backend chaining - the forwarded authentication module now supports chaining multiple backends together, allowing for flexible and secure multi-backend authentication scenarios.

Observability & metrics

• Edge-case visibility - granular HTTP observability metrics for pre-handler failures, server redirects, client-IP rewrites, CORS preflights, connection lifecycle failures, forward-proxy outcomes, reverse-proxy failures, and static-file response outcomes.
• Admin sinks - added a dropped-events admin metric for non-blocking observability sinks.
• Unix file descriptor metrics - added process.unix.file_descriptor.count (UpDownCounter) to track the change in number of unix file descriptors since the last measurement. (Linux only)
• Backend exclusion tracking - new ferron.proxy.backend.excluded counter that records each exclusion event with backend_url and reason attributes, covering passive-check failures, open circuit breakers, retry exclusion, and overloaded backends.
• Retry observability - new ferron.proxy.retry.count counter and ferron.proxy.retry.final gauge to track retry attempts and whether the final attempt succeeded.
• Connection pool metrics - new ferron.proxy.pool.hit and ferron.proxy.pool.miss counters, plus ferron.proxy.pool.idle and ferron.proxy.pool.outstanding worker-scoped gauges for per-upstream connection pool depth monitoring.
• Connect latency & TTFB - new ferron.proxy.connect.latency and ferron.proxy.ttfb histograms measuring TCP connection establishment time and time to first response byte.
• Health check instrumentation - new ferron.proxy.health.success, ferron.proxy.health.failure, and ferron.proxy.health.duration metrics for active health probe outcomes.
• Circuit breaker metrics - new ferron.proxy.circuit.state gauge (0/1/2 for Closed/HalfOpen/Open) and ferron.proxy.circuit.open_total counter tracking circuit breaker state transitions.
• Unified certificate expiration gauge - a single ferron.tls.certificate_not_after gauge is emitted by every TLS provider (manual, acme, http, local) whenever a certificate is mounted into the in-memory rustls context. The value is the certificate notAfter field as Unix epoch seconds; attributes are ferron.host (SNI hostname or IP), ferron.tls.provider (provider name), and crypto.certificate.serial_number (lowercase hex). Replaces the previous provider-specific expiration gauges.
• Baggage promotion - new baggage sub-directive in observability backend blocks (otlp, prometheus) to promote specific W3C Baggage keys into telemetry attributes for logs, metrics, and traces. Supports per-signal filtering and a max_distinct cap to prevent high-cardinality metric label explosion.
• Baggage propagation - Baggage is now propagated from incoming requests to outgoing ones, allowing distributed tracing context to be preserved across service boundaries.
• CGI/FastCGI/SCGI observability metrics - added request count, failure count, upstream duration, and stderr error metrics for the http-fcgi, http-cgi, and http-scgi modules. FastCGI also exposes connection pool wait and upstream duration metrics; CGI exposes process duration and exit code metrics; SCGI exposes upstream duration metrics.
• log_style directive - new log_style legacy|modern directive in the OTLP observability backend block to opt into OTEL-style structured logs. In modern mode, each log record publishes a short summary body plus typed per-event attributes (string, bool, integer, float) instead of the human-readable message. Access logs are remapped to OTEL semantic conventions (url.path, http.request.method, http.response.status_code, client.address, http.server.request.duration, etc.). The default legacy mode preserves existing behavior.
• Application log formatters via error_format - the error_log directive and provider file now support an error_format subdirective to choose how application (error) log messages are formatted. The text formatter (default) produces human-readable lines with timestamp, level, optional trace ID, and message. The json formatter produces structured JSON records with summary, level, target, attributes, and trace_context fields. Formatter implementations are provided by the logformat-text and logformat-json modules respectively.
• Logs for OTLP errors - Errors with the logs, metrics and traces providers are now logged.

Admin API

• Added GET /reload and GET /runtime endpoints to the admin listener.

Configuration syntax

• Globs in include directives - include "path.conf" now supports glob patterns, e.g. include "/etc/ferron/conf.d/**/*.conf".

Configuration validation

• Best-practice enforcement - ferron doctor subcommand for validating best practices across the configuration.
• Print "all good" message - a message is now printed when the configuration is valid with no diagnostics.
• JSON configuration validation results are now printed to stdout when --json is specified, improving observability for automated tools and CI/CD pipelines.
• Unused subdirectives are now reported as well as directives.

Docker

• Entrypoint configuration - Docker images now include a dedicated entrypoint config with JSON console logging, trace ID forcing, and an include /etc/ferron/conf.d/**/*.conf directive for user-provided split configurations.

Changed

Reverse proxy

• Weighted load balancing - both least_conn and round_robin algorithms now support per-upstream weight directives for proportional traffic distribution.
• Metric attributes - multiple HTTP reverse proxy metrics now embed the specific backend URL or Unix socket path as a context attribute.

DNS & TLS

• Early OCSP verification - OCSP responses are now strictly verified before being cached and stapled.
• Verbose errors - significantly improved error reporting layouts for local automatic TLS and specific TLS handshake failures.
• /var/cache/ferron-acme prioritized over user's cache dir - for Docker images with Ferron running as root, the ACME cache directory is now /var/cache/ferron-acme, which takes precedence over user's ACME cache directory.

HTTP server core

• Safe configuration reloads - configuration failures during a live reload no longer crash or stop the server; errors are logged, and execution safely continues using the previous valid configuration.
• Smarter brute-force locking - protection now locks by IP address instead of username, preventing malicious actors from intentionally locking out legitimate users.
• Accurate status codes - refactored error handling to return context-aware status codes over generic 500 or 404 errors:
  • File pipeline returns 408 Request Timeout if a request takes too long (instead of 404).
  • Basic Auth returns 429 Too Many Requests when max failed attempts are reached.
  • File serving errors return 403 Forbidden (permissions) or 400 Bad Request (invalid filenames) instead of 500.
• Support for multi-range partial static file serving - now supports serving multiple ranges from a single request, improving efficiency and reducing latency.
• String interpolation - forwarded authentication now supports interpolated string values for backend URLs.
• Security tightening - URL canonicalization now strictly rejects paths containing null bytes (\0 or %00).
• Cache cleanliness - X-LiteSpeed-Cache headers are no longer emitted by default; can be re-enabled via the emit_litespeed_headers subdirective.

Observability & tracing

• Unified request tracing - HTTP tracing now rolls up into a single ferron.request root span with nested child spans for pipelines, stages, file-serving, and error pipelines.
• Log correlation - OTLP request and access logs now include the active request span context out of the box.
• Backend exporting - admin API metrics are now also pushed directly to configured observability backends, not just the local admin endpoint.
• Cardinality control - Prometheus label values are now sanitized to heavily reduce high-cardinality label inflation.
• Structured log events - every log emission site now carries a short OTEL-friendly summary plus typed attributes, enabling downstream OTLP consumers to receive structured events without changing existing console or file log output.
• Trace ID in console and file logs - console and file loggers now prefix log messages with [trace=<span_id>] when a trace context is available, enabling grep-based filtering by trace ID.
• Trace context injection for CGI/FastCGI/PHP-FPM/SCGI - trace context headers are now automatically propagated to the backend environment via CGI/FastCGI/PHP-FPM/SCGI.
• Incoming trace context discarded by default - Ferron now generates a fresh trace ID for every request by default, discarding incoming traceparent/tracestate/baggage headers unless trust_request true is configured. Existing deployments relying on incoming trace context must add trust_request true to the trace block.
• Sanitized trace header injection - inject_trace_headers now removes any existing traceparent, tracestate, and baggage headers before injecting new values, preventing header duplication or conflicts.

Core runtime

• Unified durations - improved configuration-wide consistency for duration formatting values.
• Graceful shutdown - the server process now handles standard Unix SIGTERM signals for seamless graceful shutdowns.
• Frictionless local TLS - the server now issues a clean warning if local automatic TLS is configured but the cache directory isn't writable, instead of refusing to boot.

Docker

• Split configuration layout - Docker images now use a two-file layout: /etc/ferron/ferron.conf as the entrypoint config and /etc/ferron/conf.d/ for user configuration files. Docker Compose bind mounts now target the conf.d/ directory.

Package configuration

• Log rotation and structured logging - Default package configurations now include log rotation settings and commented-out structured logging and trace ID format options.

Fixed

Reverse proxy

• Fixed a bug where pool limits weren't being respected when pulling connections from the pool, leading to possible handle exhaustion.
• Fixed a bug where reverse proxy boolean subdirectives with empty values (implying true) were being ignored.
• Fixed an issue where the proxy failed to strip headers specified by the Connection header per RFC 7230.

DNS & ACME

• Fixed an "invalid socket address" error that broke RFC 2136 dynamic DNS updates for the ACME DNS-01 challenge.
• Resolved an edge case where OCSP stapling failed to immediately fetch the response after new certificates were registered.

HTTP server core

• Auth bypass closed - fixed a critical flaw where a misconfigured forwarded authentication block could result in bypassing authentication entirely.
• Cache thundering herd fixed - implemented request coalescing for cache misses to prevent thundering herd scenarios when multiple requests hit the same uncached resource simultaneously.
• Several HTTP/1.x protocol handling bugs fixed - fixed chunked-length encoding DoS vulnerability and other protocol-related issues (see vibeio-http changelog).
• Fixed a 500 Internal Server Error when using the auth_to { ... } syntax inside forwarded authentication blocks.
• Fixed a bug where case-insensitive HTTP cache control directives were not recognized correctly.
• Fixed a bug where CONNECT requests with authority-form URIs were erroneously blocked by the URL canonicalizer.
• Fixed a bug where HTTP connections couldn't be accepted on 32-bit Windows (see vibeio changelog; GitHub issue).
• Fixed a bug where HTTP connections were accepted by only one OS thread on Windows.
• Fixed a bug where HTTP timeout durations were not being respected correctly.
• Fixed a bug where TLS certificate resolver from domain name level higher (non-wildcard) was incorrectly used for TLS handshakes if the one from the domain name level matching the requested SNI isn't present.
• Fixed HTTP-to-HTTPS redirects to correctly target the original requested URL rather than internal rewritten URLs.

Observability

• Log injection fixed - implemented strict sanitization of log fields to prevent potential log injection attacks for plain-text logs via malicious header values or other user input.
• Fixed a data blind spot where malformed and timed-out requests rejected before normal handler completion went uncounted by the observability pipeline.
• The server now removes sensitive HTTP headers from access logs (such as cookie, authorization), to prevent sensitive data exposure in log output.
• Corrected inaccurate memory metrics that were calculating values relative to initial memory usage instead of absolute usage.

Security

• DNS rebinding fixed - closed a vulnerability where forward-proxy DNS validation could be bypassed via a race condition combined with a DNS rebinding attack.
• Fixed an issue where forward-proxy allowed ports and denied IP addresses were being treated as additive rather than strictly respecting user configuration overrides.

Runtime operations

• Fixed an Admin API-initiated reload loop that caused infinite configuration reload loops.
• Fixed admin API over-redacting configuration directives in /config endpoint responses, which could lead to confusion when verifying configuration values.
• Eliminated a rate limiting race condition when initializing a brand new key bucket, which previously allowed traffic to briefly exceed configured capacities.
• Fixed manual TLS session ticket key rotation to properly read from configured key files instead of silently falling back to in-memory generation.
• Fixed a bug on Linux where io_uring could not be explicitly disabled through the server configuration file.
• Fixed an edge case where cached responses replaced by non-cached default error pages could be returned stale.