runtime.toml Retain, Watchdog, And Fault Configuration

runtime.toml defines how one truST runtime instance executes, exposes control surfaces, and participates in discovery, mesh, and runtime-cloud workflows.

Unknown fields are rejected. The file is validated by the same schema path used by trust-runtime validate, the browser IDE, and runtime startup.

This is the main reference for runtime retain policy, watchdog settings, and runtime fault policy.

Minimal Example

[bundle]
version = 1

[resource]
name = "main"
cycle_interval_ms = 100

[runtime.control]
endpoint = "unix:///tmp/trust-runtime.sock"
mode = "production"

[runtime.log]
level = "info"

[runtime.retain]
mode = "none"
save_interval_ms = 1000

[runtime.watchdog]
enabled = false
timeout_ms = 5000
action = "halt"

[runtime.fault]
policy = "halt"

Core Sections

[bundle]

Key	Type	Required	Notes
version	integer	yes	Must currently be 1.

[resource]

Key	Type	Required	Notes
name	string	yes	Logical resource/runtime name. Must not be empty.
cycle_interval_ms	integer	yes	Main scan interval in milliseconds. Must be >= 1.

Optional task overrides:

[[resource.tasks]]
name = "Fast"
interval_ms = 10
priority = 1
programs = ["Main"]
single = "Main"

Each task needs:

• name
• interval_ms >= 1
• priority
• at least one entry in programs
• optional single

Runtime Sections

[runtime]

Key	Type	Required	Default	Notes
execution_backend	string	no	vm	Only vm is accepted. interpreter is explicitly rejected.

[runtime.control]

Key	Type	Required	Default	Notes
endpoint	string	yes	none	unix://... or tcp://.... Must not be empty.
auth_token	string	no	none	Required for tcp:// endpoints.
mode	string	no	production	production or debug.
debug_enabled	bool	no	derived	Defaults to true in debug mode and false in production.

[runtime.log]

Key	Type	Required	Notes
level	string	yes	Logging level string. Must not be empty.

[runtime.retain] (retain policy)

Key	Type	Required	Default	Notes
mode	string	yes	none	none or file.
path	string	only for file	none	Required when mode = "file".
save_interval_ms	integer	yes	none	Must be >= 1.

[runtime.watchdog] (watchdog and fault policy)

Key	Type	Required	Notes
enabled	bool	yes	Enables scan watchdog enforcement.
timeout_ms	integer	yes	Must be >= 1.
action	string	yes	halt, safe_halt, or restart.

[runtime.fault] (fault policy)

Key	Type	Required	Notes
policy	string	yes	halt, safe_halt, or restart.

Networked / Optional Interfaces

[runtime.web]

Defaults when omitted:

[runtime.web]
enabled = true
listen = "0.0.0.0:8080"
auth = "local"
tls = false

Accepted keys:

• enabled
• listen
• auth = "local" | "token"
• tls

Validation constraints:

Condition	Requirement	Example
auth = "token"	runtime.control.auth_token must be set	auth = "token" with runtime.control.auth_token = "secret"
tls = true	runtime.tls.mode must not be "disabled"	enable [runtime.tls] before serving HTTPS
remote listen + runtime.tls.require_remote = true	tls must be true	listen = "0.0.0.0:8080" requires tls = true

[runtime.tls]

Defaults when omitted:

[runtime.tls]
mode = "disabled"
require_remote = false

Accepted keys:

• mode = "disabled" | "self-managed" | "provisioned"
• cert_path
• key_path
• ca_path
• require_remote

Validation constraints:

Condition	Requirement	Example
mode != "disabled"	set both cert_path and key_path	mode = "self-managed" with PEM files
mode = "provisioned"	set ca_path in addition to cert/key	provisioned PKI bundle

[runtime.deploy]

Key	Type	Default	Notes
require_signed	bool	false	Enforces signed deployment artifacts.
keyring_path	string	none	Required when require_signed = true.

[runtime.discovery]

Defaults when omitted:

[runtime.discovery]
enabled = true
service_name = "truST"
advertise = true
interfaces = []

Accepted keys:

• enabled
• service_name
• advertise
• interfaces = ["eth0", ...]
• host_group

[runtime.mesh]

Defaults when omitted:

[runtime.mesh]
enabled = false
role = "peer"
listen = "0.0.0.0:5200"
connect = []
tls = false
publish = []
subscribe = {}
zenohd_version = "1.7.2"
plugin_versions = {}

Accepted keys:

• enabled
• role = "peer" | "client" | "router"
• listen
• connect
• tls
• auth_token
• publish
• subscribe
• zenohd_version
• plugin_versions

Validation constraints:

Condition	Requirement	Example
runtime.mesh.tls = true	runtime TLS must be enabled	mesh listener using the runtime TLS certificate set
remote mesh listen + runtime.tls.require_remote = true	mesh TLS must be on	listen = "0.0.0.0:5200" with tls = true

[runtime.cloud]

This section shapes runtime-cloud policy inside runtime.toml.

Key	Type	Default	Notes
profile	string	dev	dev, plant, or wan

Optional subsections:

[runtime.cloud.wan]
allow_write = [
  { action = "cfg_apply", target = "site-b/*" }
]

[runtime.cloud.links]
transports = [
  { source = "runtime-a", target = "runtime-b", transport = "zenoh" }
]

Allowed transport values:

• realtime
• zenoh
• mesh
• mqtt
• modbus-tcp
• opcua
• discovery
• web

[runtime.observability]

Defaults when omitted:

[runtime.observability]
enabled = false
sample_interval_ms = 1000
mode = "all"
include = []
history_path = "history/historian.jsonl"
max_entries = 20000
prometheus_enabled = true
prometheus_path = "/metrics"
alerts = []

Validation constraints:

Condition	Requirement	Example
always	sample_interval_ms >= 1	sample_interval_ms = 1000
always	max_entries >= 1	max_entries = 20000
always	mode is all or allowlist	mode = "allowlist"
mode = "allowlist"	include must not be empty	include = ["PROGRAM Main.Pressure"]
prometheus_enabled = true	prometheus_path must start with /	prometheus_path = "/metrics"

Alert entries support:

[[runtime.observability.alerts]]
name = "HighPressure"
variable = "PROGRAM Main.Pressure"
above = 8.5
debounce_samples = 3
hook = "log"

Each alert needs:

Field	Requirement	Example
name	required	"HighPressure"
variable	required	"PROGRAM Main.Pressure"
above / below	provide at least one threshold	above = 8.5
debounce_samples	must be >= 1	debounce_samples = 3

[runtime.opcua]

Defaults when omitted:

[runtime.opcua]
enabled = false
listen = "0.0.0.0:4840"
endpoint_path = "/"
namespace_uri = "urn:trust:runtime"
publish_interval_ms = 250
max_nodes = 128
expose = []
security_policy = "basic256sha256"
security_mode = "sign_and_encrypt"
allow_anonymous = false

Validation constraints:

Condition	Requirement	Example
always	listen, endpoint_path, and namespace_uri must not be empty	listen = "0.0.0.0:4840"
always	endpoint_path must start with /	endpoint_path = "/"
always	publish_interval_ms >= 1	publish_interval_ms = 250
always	max_nodes >= 1	max_nodes = 128
enabled = true	allow anonymous access or set both username and password	authenticated endpoint with user/password
security_policy	must be none, basic256sha256, or aes128sha256rsaoaep	security_policy = "basic256sha256"
security_mode	must be none, sign, or sign_and_encrypt	security_mode = "sign_and_encrypt"

Validation Workflow

Use this loop whenever you edit runtime.toml:

trust-runtime build --project ./my-plc --sources src
trust-runtime validate --project ./my-plc
trust-runtime ctl --project ./my-plc status

Related

• I/O Binding
• Runtime Cloud
• Compile, Validate, Reload