Glossary

Terms used throughout the codebase and the official documentation. The glossary leans on the configuration vocabulary defined in pkg/config/dynamic and pkg/config/static.

Routing concepts

• Entry point — a network listener with a port, protocol, and TLS configuration. Defined statically in pkg/config/static/entrypoints.go. Each entry point can carry HTTP, HTTP/2, HTTP/3, TCP, or UDP traffic.
• Router — a rule plus a list of middlewares plus a target service. HTTP routers live in pkg/config/dynamic/http_config.go (Router); TCP and UDP variants live in tcp_config.go and udp_config.go.
• Rule — the predicate string a router matches against (e.g. Host(\api.example.com`) && PathPrefix(`/v1`)). Parsed by pkg/rules/parser.go`.
• Service — the destination of a router. Most commonly a load-balanced set of upstream URLs. Mirroring, weighted, and failover services exist too. See pkg/config/dynamic/http_config.go (Service) and pkg/server/service/service.go.
• Middleware — a request transformer attached to a router. Each middleware type has its own implementation under pkg/middlewares/<name> and a config struct in pkg/config/dynamic/middlewares.go.
• Provider — a source of dynamic configuration. Implements provider.Provider in pkg/provider/provider.go. Examples: Docker, Kubernetes (CRD/Ingress/Gateway), file, Consul KV, Nomad.
• TLS option — a named TLS configuration template (cipher suites, min version, mTLS settings, ALPN). Live in pkg/tls/tls.go.
• Certificate resolver — an entity that obtains TLS certificates dynamically, most often via ACME (pkg/provider/acme). Tailscale resolvers also exist (pkg/provider/tailscale).

Configuration vocabulary

• Static configuration — settings frozen at startup. Schema in pkg/config/static/static_config.go.
• Dynamic configuration — settings that can change at runtime via providers. Top-level type is dynamic.Configuration in pkg/config/dynamic/http_config.go.
• Runtime configuration — the in-memory dynamic configuration with attached status (used by the dashboard). Lives in pkg/config/runtime.
• Constraint — a label selector applied to provider-discovered objects to include or exclude them. Implemented in pkg/provider/constraints/.
• Default rule — a Go template (per provider) used to build a router rule when none is defined on the discovered service. Set on the provider config.

Networking and protocols

• HTTP/3 — QUIC-based HTTP. Supported by entry points via pkg/server/server_entrypoint_tcp_http3.go.
• HTTP/2 — supported on TCP entry points, including HTTP/2 Cleartext (h2c).
• gRPC / gRPC-Web — gRPC works natively over HTTP/2; gRPC-Web is bridged by pkg/middlewares/grpcweb.
• WebSocket — supported transparently by the HTTP reverse proxies in pkg/proxy/fast and pkg/proxy/httputil.
• PROXY protocol — supported on TCP entry points; trusted networks live in entry-point configuration.
• SNI / ALPN — used by pkg/muxer/tcp to multiplex TLS, HTTP, and raw TCP on the same port.

Load balancing and health

• WRR — weighted round robin. Implementation in pkg/server/service/loadbalancer/wrr.
• P2C — power-of-two-choices. Implementation in pkg/server/service/loadbalancer/p2c.
• HRW — highest random weight (rendezvous hashing). Implementation in pkg/server/service/loadbalancer/hrw.
• Mirror — duplicates traffic across services. Implementation in pkg/server/service/loadbalancer/mirror.
• Failover — primary/fallback service. Implementation in pkg/server/service/loadbalancer/failover.
• Sticky session — cookie-based affinity. Implementation in pkg/server/service/loadbalancer/sticky.go and the cookie helper in pkg/server/cookie.
• Health check — periodic probe against an upstream URL. Server-side logic in pkg/healthcheck and pkg/server/service/loadbalancer/healthcheck.go (per-LB).

Observability

• Access log — per-request log line. Implemented in pkg/middlewares/accesslog. Supports CLF and JSON formats.
• Capture middleware — internal middleware that records latency, byte counts, and status for downstream observability middlewares (pkg/middlewares/capture).
• Metrics registry — typed metrics interface (pkg/observability/metrics/metrics.go) with backends for Prometheus, OTLP, Datadog, StatsD, InfluxDB 2.
• Tracer — OpenTelemetry tracer wired in pkg/observability/tracing.
• Hub — Traefik Hub integration hooks. Some hooks live in this open-source repo (pkg/provider/aggregator/aggregator.go mentions hub providers); the actual integration is shipped separately.

ACME / TLS

• ACME challenge — HTTP-01 (pkg/provider/acme/challenge_http.go) or TLS-ALPN-01 (pkg/provider/acme/challenge_tls.go) or DNS-01 (provided by go-acme/lego plugins).
• Resolver — a named ACME or external resolver in static config. Routers reference resolvers by name to request certificates.
• OCSP stapling — implemented in pkg/tls/ocsp.go. Enabled by the OCSP static-config block.
• SPIFFE / SVID — workload identity integration via github.com/spiffe/go-spiffe/v2. Wired in cmd/traefik/traefik.go.

Plugins

• Yaegi plugin — a Go middleware loaded at runtime via the Yaegi interpreter. See pkg/plugins/middlewareyaegi.go.
• Wasm plugin — a WebAssembly middleware loaded via Wazero. See pkg/plugins/middlewarewasm.go.
• Plugin manifest — .traefik.yml shipped with each plugin; parsed by pkg/plugins/manager.go.

Process model

• Routines pool — a safe.Pool (pkg/safe) of context-aware goroutines used for provider polling and configuration application.
• Server — the top-level lifecycle owner in pkg/server/server.go. Owns the entry points, the watcher, the observability manager, and the routines pool.
• Configuration watcher — pkg/server/configurationwatcher.go. Receives, deduplicates, transforms, and dispatches dynamic configurations.
• Router factory — pkg/server/routerfactory.go. Builds the live router tree from a dynamic.Configurations snapshot.
• Aggregator — pkg/provider/aggregator/aggregator.go. Multiplexes multiple providers behind a single provider.Provider interface.