3.11. state section

a state has a unique name. other that processes, states can be defined without a fixed node-assignment. a state without an explicit node assignment will inherit the node from a depending process.

there are two types of states:

• a set of 3 shell-commands: CHECK, UP and DOWN the shell exit-code (return value) of the CHECK command is interpreted to decide whether a state is UP or DOWN.

• a TCP tunnel state a TCP/IP tunnel established by the ln_daemons. only if tcp_tunnel_exit_target and tcp_tunnel_exit_node is specified.

3.11.1. check

shell command to execute to decide whether a state is currently UP or DOWN. the shell exit-code (return value) of the CHECK command is interpreted to decide whether a state is UP or DOWN. a 0 exit-code is commonly interpreted as “success” and the state is assumed to be UP. every non-zero exit-code will cause the state to be assumed DOWN.

3.11.2. up

shell command to execute to bring a state UP.

If a state is requested UP and the manager does not currently trust its last known state, it may first trigger a CHECK command instead of directly executing UP.

3.11.3. down

shell command to execute to bring a state DOWN.

As with UP, the manager may first run CHECK if the current state is not known or is considered outdated.

3.11.4. min_check_interval

number of seconds to assume that last state-result is still valid. (default: 30 since version 0.13.11)

The manager will not re-run CHECK more often than this unless a forced re-check is needed, for example because there were previous errors or because no result has been recorded yet.

3.11.5. tcp_tunnel_exit_node

only for TCP tunnel states.

Name of the node or host on which the tunnel target exists.

3.11.6. tcp_tunnel_exit_target

only for TCP tunnel states.

Target address for the far end of the tunnel in HOST:PORT form.

3.11.7. tcp_tunnel_entry_port

only for TCP tunnel states.

Optional fixed local entry port for the tunnel. If omitted, ln_manager will use the same PORT from tcp_tunnel_exit_target.

3.11.8. flags

list of one or more of these flags:

os_state

request that ln_daemon treats this as an operating-system state when executing the state commands. The detailed semantics are implemented on the daemon side.

autostart

whenever a daemon connection for one of the state’s assigned nodes becomes available, ln_manager automatically requests this state to go UP.

need_check_after_up

after a successful UP or DOWN request, do not trust the immediate state notification as final. Instead, reset the cached state to unknown and require a fresh CHECK before the state is considered reliably known again.

3.11.9. node

node where this state is assigned to.

Unlike processes, a state can omit an explicit node. In that case ln_manager derives the node assignment from objects that depend on this state.

3.11.10. depends_on

list of dependencies that need to be fulfilled before the UP or DOWN command can be executed.

This works like depends_on, but applies to state operations instead of process startup.

Dependencies are considered when requesting UP or DOWN. They are not automatically enforced for CHECK.

3.11.11. depends_on_restart

This works like depends_on_restart, but applies to states. If such a dependency goes away, ln_manager keeps the resulting error condition until the affected state has been re-established.

3.11.12. provides

This works like provides in process section.

It allows a state to advertise that it can provide a named service or topic on demand. If multiple configured processes or states provide the same name, the one with the highest priority wins.

3.11.13. output_buffer_size

This setting is inherited from the shared output configuration code, but unlike processes it is currently not forwarded as a state-specific request parameter to ln_daemon. In the current Python manager code it therefore has no documented practical effect for states.

3.11.14. max_queued_output_bytes

Maximum number of output bytes ln_manager queues for this state’s displayed output before it starts dropping already buffered text, unless such skipping is disabled globally for that object type.

3.11.15. max_output_lines

Maximum number of output lines kept in the ln_manager output widget for this state.