Backends

The [[backends]] entries define upstream targets. Each route references a backend by its address string (must match exactly). Dynamic: hot-reloadable.

Fields (per backend)

Key	Default	Description
address	-	host:port (or bracketed IPv6). In orchestrated setups this is usually a service name (Docker Compose, Kubernetes DNS, etc.). Used as the pool key: must match exactly what routes reference.
http_version	null (preserve)	Protocol to use when connecting to this backend. "http11", "http2", or "preserve" (negotiate based on what the client used).
health_check	null (off)	Optional active health probe. When set, the proxy tracks per-upstream health and returns 502 to clients when the backend is marked unhealthy. See Health checks below.

Example

YAML

backends:
 - address: "backend-a:9000"
 http_version: preserve
 - address: "backend-b:9000"
 http_version: http11

TOML

[[backends]]
address = "backend-a:9000"
http_version = "preserve"

[[backends]]
address = "backend-b:9000"
http_version = "http11"

Health checks

Optional active probes via health_check on a [[backends]] entry. When configured, a background task probes the backend on an interval. If consecutive failures exceed unhealthy_threshold, the backend is marked unhealthy and the proxy returns 502 for matching routes instead of waiting on TCP timeouts. Once consecutive successes reach healthy_threshold, the backend is marked healthy again. Dynamic: hot-reloadable.

If you omit health_check, the backend is always treated as healthy (no background probing).

Key	Default	Description
type	tcp	tcp (TCP 3-way handshake) or http (HTTP/1.1 GET to http://{address}{path}; plain HTTP only, no TLS to upstream).
path	-	Required when type = "http": must start with / (e.g. / or /ready). Ignored for tcp.
expected_status	200	For http only: response status must match (e.g. 200, 204).
interval_secs	10	Time between probes.
timeout_secs	5	Per-probe budget (must be ≤ interval_secs). Encompasses connect, request, and body drain for http.
unhealthy_threshold	3	Consecutive failed probes before marking upstream unhealthy.
healthy_threshold	2	Consecutive successful probes before marking upstream healthy again.

Example (HTTP probe):

YAML

backends:
 - address: "app:8080"
 http_version: http11
 health_check:
 type: http
 path: /ready
 expected_status: 200

TOML

[[backends]]
address = "app:8080"
http_version = "http11"
# HTTP GET http://app:8080/ready must return 200
health_check = { type = "http", path = "/ready", expected_status = 200 }

Recommended usage: most useful when Huginn Proxy is the main resiliency layer (VM/bare-metal/Docker Compose, or direct upstream addresses). In orchestrators (e.g. Kubernetes Service), health checks are optional: they can overlap with readiness filtering, but can still be valuable for faster failover at the proxy level.

Limitation: the HTTP probe does not use TLS to the upstream: use a TCP check, or an HTTP path that responds over cleartext.

Backend pool

The [backend_pool] block configures the HTTP connection pool for proxy → backend traffic. Dynamic: changing it triggers pool recreation and draining of old connections.

YAML

backend_pool:
 enabled: true
 idle_timeout: 90
 pool_max_idle_per_host: 0

TOML

[backend_pool]
enabled = true
idle_timeout = 90
pool_max_idle_per_host = 0

Key	Default	Description
enabled	true	Enable pooling (false = new connection per request; not recommended for production).
idle_timeout	90	Seconds before an idle pooled connection is closed.
pool_max_idle_per_host	0	Max idle connections per backend host; 0 = unlimited.

Load balancing

Define one or more backends, then reference a backend address on each route. When a route lists several backend addresses, traffic is spread with round-robin. In practice, replicas and health are often handled outside the proxy (scheduler, Service endpoints).

Active health probes are available via health_check. See Health checks above. Least-connections and weighted routing are not implemented.