Struct steno::Node

pub struct Node { /* private fields */ }

Describes a node in the saga DAG

There are three kinds of nodes you can add to a graph:

• an action (see Node::action), which executes a particular Action with an associated undo action
• a constant (see Node::constant), which is like an action that outputs a value that’s known when the DAG is constructed
• a subsaga (see Node::subsaga), which executes another DAG in the context of this saga

Each of these node types has a node_name and produces an output. Other nodes that depend on this node (directly or indirectly) can access the output by looking it up by the node name using crate::ActionContext::lookup:

• The output of an action node is emitted by the action itself.
• The output of a constant node is the value provided when the node was created (see Node::constant).
• The output of a subsaga node is the output of the subsaga itself. Note that the output of individual nodes from the subsaga DAG is not available to other nodes in this DAG. Only the final output is available.

Implementations

impl Node

pub fn action<N: AsRef<str>, L: AsRef<str>, A: SagaType>( node_name: N, label: L, action: &dyn Action<A> ) -> Node

Make a new action node (see Node)

This node is used to execute the given action. The action’s output will be available to dependent nodes by looking up the name node_name. See Action for more information.

pub fn constant<N: AsRef<str>>(node_name: N, value: Value) -> Node

Make a new constant node (see Node)

This node immediately emits value. Why would you want this? Suppose you’re working with some saga action that expects input to come from some previous saga node. But in your case, you know the input up front. You can use this to provide the value to the downstream action.

pub fn subsaga<N1: AsRef<str>, N2: AsRef<str>>( node_name: N1, dag: Dag, params_node_name: N2 ) -> Node

Make a new subsaga node (see Node)

This is used to insert a subsaga into another saga. The output of the subsaga will have name node_name in the outer saga. The subsaga’s DAG is described by dag. Its input parameters will come from node params_node_name in the outer saga.

Trait Implementations

impl Clone for Node

fn clone(&self) -> Node

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Node

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.