Expand description
§phlow - A Dynamic Rule-Based Workflow Engine
phlow is a flexible and extensible rule-based workflow engine written in Rust.
It allows users to define and execute dynamic decision trees and conditional workflows
using JSON-based configurations and embedded scripting via Rhai.
§Features
- Dynamic workflows with JSON-defined rules
- Embedded scripting with Rhai for advanced expressions
- Conditional branching with custom operators (
starts_with,ends_with,search) - Step-based execution with context-aware evaluation
- Extensible engine with pluggable functions
§Example: Decision Tree for Club Membership Approval
This example demonstrates a decision tree to determine if a person can become a club member.
use phlow_engine::{Phlow, Context};
use phs::build_engine;
use valu3::prelude::*;
use valu3::json;
use std::sync::Arc;
let decision_tree = json!({
"steps": [
{
"condition": {
"left": "params.age",
"right": 18,
"operator": "greater_than_or_equal"
},
"then": {
"steps": [
{
"condition": {
"left": "params.income",
"right": 5000.0,
"operator": "greater_than_or_equal"
},
"then": {
"return": "Approved"
},
"else": {
"return": "Rejected - Insufficient income"
}
}
]
},
"else": {
"return": "Rejected - Underage"
}
}
]
});
let phlow = Phlow::try_from_value(&decision_tree, None)?;
let mut context = Context::from_main(json!({ "age": 20, "income": 6000.0 }));
let result = phlow.execute(&mut context).await?;
println!("Decision: {:?}", result);§Modules
phlow- Main structure containing pipelines and execution logic.context- Manages execution state and variable storage.pipeline- Defines sequential execution of processing steps.step_worker- Handles conditional logic and step execution.script- Integrates Rhai scripting for dynamic evaluation.- [
engine] - Configures and extends the scripting engine. condition- Defines logical operators and conditions.collector- Logs execution steps and tracks workflow state.
§Architecture Overview
The phlow engine processes a workflow pipeline composed of steps. Each step can:
- Evaluate conditions (e.g., comparisons, regex matching)
- Execute scripts for computations
- Branch execution based on conditions
- Store and reference previous step outputs
§Execution Flow
- The engine receives an input JSON workflow definition.
- The
phlowinstance parses and validates the workflow. - The workflow executes step-by-step, evaluating conditions and executing actions.
- The final result is returned to the caller.
§Advanced Usage
§Adding Custom Plugins
Users can extend phlow by adding custom functions to the execution engine. The phlow engine supports extending functionality through custom Rhai functions and repositories that can be injected into the scripting environment.
For detailed examples of extending the engine, see the phs module documentation
and the build_engine function.
§Handling Execution Errors
Errors during workflow execution are returned as Result<T, PhlowError>:
use phlow_engine::{Phlow, Context};
use valu3::prelude::*;
use valu3::json;
let workflow = json!({
"steps": [
{
"return": "Success"
}
]
});
let phlow = Phlow::try_from_value(&workflow, None)?;
let mut context = Context::from_main(json!({"key": "value"}));
match phlow.execute(&mut context).await {
Ok(result) => println!("Execution succeeded: {:?}", result),
Err(err) => eprintln!("Execution failed: {:?}", err),
}§License
This project is licensed under the MIT License.
Re-exports§
pub use phlow::Phlow;pub use phlow::PhlowError;pub use phs;