Your First Real Workflow: Leave Request

Build a real-world Leave Request workflow with human tasks, business logic, and notifications.

What You’ll Build

A complete workflow that:

Collects leave request details from the user
Checks vacation balance
Routes based on number of days
Sends approval/denial emails
Updates HR system

State types you’ll learn:

HumanTask - Wait for user input
Choice - Conditional logic
EvaluatePolicy - Business rules
Task - Execute activities
Parallel - Send multiple notifications
Wait - Time-based delays (bonus)
Receive - External events (bonus)

Complete Leave Request Workflow

Create leave-request-app.yaml:


apiVersion: cascade.io/v1
kind: Application
metadata:
  name: hr-leave-request
spec:
  workflows:
    - name: leave_request_flow
      description: "HR Leave Request Process"
      start: RequestDetails
      states:
        # ==========================================
        # 1. HUMANTASK STATE - Collect user input
        # ==========================================
        - name: RequestDetails
          type: HumanTask
          description: "Employee submits leave request"
          ui:
            schema: urn:cascade:schema:leave_request_form
            target: appsmith
          next: CheckVacationBalance
 
        # ==========================================
        # 2. CHOICE STATE - Conditional branching
        # ==========================================
        - name: CheckVacationBalance
          type: Choice
          description: "Check if employee has enough vacation days"
          choices:
            - variable: $.state.days_requested
              numericLessThanEquals: $.context.vacation_balance
              next: SelectApprovalPath
            - default: InsufficientBalance
 
        # ==========================================
        # 3. EVALUATE POLICY STATE - Business rules
        # ==========================================
        - name: SelectApprovalPath
          type: EvaluatePolicy
          description: "Determine approval workflow based on days"
          policy: urn:cascade:policy:leave_approval_routing
          engine: opa  # Options: opa, dmn, wasm
          parameters:
            days_requested: $.state.days_requested
            department: $.context.department
          resultPath: $.policy_decision
          next: DecideRoute
 
        # ==========================================
        # 4. CHOICE STATE - Route based on policy
        # ==========================================
        - name: DecideRoute
          type: Choice
          choices:
            - variable: $.policy_decision.approval_type
              stringEquals: "auto_approve"
              next: AutoApprove
            - variable: $.policy_decision.approval_type
              stringEquals: "manager_approval"
              next: ManagerApprovalTask
            - default: ExecutiveApproval
 
        # ==========================================
        # Path A: Auto-approve short leaves
        # ==========================================
        - name: AutoApprove
          type: Task
          resource: urn:cascade:activity:approve_leave
          parameters:
            instance_id: $.id
            approval_type: "automatic"
          resultPath: $.approval_result
          next: SendApprovalNotifications
 
        # ==========================================
        # Path B: Manager approval task
        # ==========================================
        - name: ManagerApprovalTask
          type: HumanTask
          description: "Manager reviews and approves/denies"
          ui:
            schema: urn:cascade:schema:approval_form
            target: appsmith
          next: EvaluateManagerDecision
 
        - name: EvaluateManagerDecision
          type: Choice
          choices:
            - variable: $.state.manager_approved
              booleanEquals: true
              next: SendApprovalNotifications
            - default: Denied
 
        # ==========================================
        # Path C: Executive approval (for long leaves)
        # ==========================================
        - name: ExecutiveApproval
          type: HumanTask
          description: "Executive reviews extended leave"
          ui:
            schema: urn:cascade:schema:executive_approval_form
            target: appsmith
          next: EvaluateExecutiveDecision
 
        - name: EvaluateExecutiveDecision
          type: Choice
          choices:
            - variable: $.state.executive_approved
              booleanEquals: true
              next: SendApprovalNotifications
            - default: Denied
 
        # ==========================================
        # 5. PARALLEL STATE - Send notifications
        # ==========================================
        - name: SendApprovalNotifications
          type: Parallel
          description: "Notify employee and update systems"
          branches:
            - name: SendEmployeeEmail
              type: Task
              resource: urn:cascade:activity:send_email
              parameters:
                recipient: $.context.employee_email
                subject: "Your leave request has been approved"
                template: "leave_approved"
 
            - name: NotifyHR
              type: Task
              resource: urn:cascade:activity:notify_hr
              parameters:
                employee_id: $.context.employee_id
                leave_dates: $.state.leave_dates
                days: $.state.days_requested
 
            - name: UpdateCalendar
              type: Task
              resource: urn:cascade:activity:update_calendar
              parameters:
                employee_id: $.context.employee_id
                leave_dates: $.state.leave_dates
          next: Complete
 
        # ==========================================
        # Denial path
        # ==========================================
        - name: Denied
          type: Task
          resource: urn:cascade:activity:deny_leave
          parameters:
            instance_id: $.id
            reason: $.state.denial_reason
          next: SendDenialNotification
 
        - name: SendDenialNotification
          type: Task
          resource: urn:cascade:activity:send_email
          parameters:
            recipient: $.context.employee_email
            subject: "Your leave request has been denied"
            template: "leave_denied"
          next: Complete
 
        # ==========================================
        # Insufficient balance path
        # ==========================================
        - name: InsufficientBalance
          type: Task
          resource: urn:cascade:activity:insufficient_balance_email
          parameters:
            recipient: $.context.employee_email
            available_balance: $.context.vacation_balance
            requested_days: $.state.days_requested
          next: Complete
 
        # ==========================================
        # Final state
        # ==========================================
        - name: Complete
          type: Task
          end: true

Understanding Each Part

1. HumanTask State: RequestDetails


- name: RequestDetails
  type: HumanTask
  ui:
    schema: urn:cascade:schema:leave_request_form
    target: appsmith
  next: CheckVacationBalance

What it does:

Waits for user to interact with UI form
Collects: employee name, dates, reason
Stores input in $.state
Moves to CheckVacationBalance when user submits

Output example:


{
  "state": {
    "employee_name": "John Doe",
    "leave_dates": ["2025-11-15", "2025-11-16"],
    "days_requested": 2,
    "reason": "Vacation"
  }
}

2. Choice State: CheckVacationBalance


- name: CheckVacationBalance
  type: Choice
  choices:
    - variable: $.state.days_requested
      numericLessThanEquals: $.context.vacation_balance
      next: SelectApprovalPath
    - default: InsufficientBalance

What it does:

Compares days_requested (from form) with vacation_balance (from context)
If balance is sufficient → routes to SelectApprovalPath
Otherwise → routes to InsufficientBalance
Execution time: <0.1ms (in-process logic)

Available operators:

stringEquals, stringLessThan, stringContains
numericEquals, numericLessThan, numericGreaterThan
booleanEquals
Combinations: and, or, not

3. EvaluatePolicy State: SelectApprovalPath


- name: SelectApprovalPath
  type: EvaluatePolicy
  policy: urn:cascade:policy:leave_approval_routing
  engine: opa  # or dmn, wasm
  parameters:
    days_requested: $.state.days_requested
    department: $.context.department
  resultPath: $.policy_decision
  next: DecideRoute

What it does:

Evaluates complex business rules (OPA Rego policy)
Passes employee info and request to policy engine
Gets decision back: auto_approve, manager_approval, or executive_approval
Typical execution time: <5ms (OPA) or 10-50ms (DMN)

Example OPA policy (urn:cascade:policy:leave_approval_routing):


package leave_approval

default approval_type = "manager_approval"

approval_type = "auto_approve" {
  input.days_requested <= 2
  input.department == "Engineering"
}

approval_type = "executive_approval" {
  input.days_requested > 10
}

4. Choice State: DecideRoute


- name: DecideRoute
  type: Choice
  choices:
    - variable: $.policy_decision.approval_type
      stringEquals: "auto_approve"
      next: AutoApprove
    - variable: $.policy_decision.approval_type
      stringEquals: "manager_approval"
      next: ManagerApprovalTask
    - default: ExecutiveApproval

What it does:

Routes workflow to different approval paths based on policy decision
Shows how Choice and EvaluatePolicy work together

5. Parallel State: SendApprovalNotifications


- name: SendApprovalNotifications
  type: Parallel
  branches:
    - name: SendEmployeeEmail
      type: Task
      resource: urn:cascade:activity:send_email
      parameters:
        recipient: $.context.employee_email
        subject: "Your leave request has been approved"
        template: "leave_approved"
 
    - name: NotifyHR
      type: Task
      resource: urn:cascade:activity:notify_hr
      parameters:
        employee_id: $.context.employee_id
        leave_dates: $.state.leave_dates
 
    - name: UpdateCalendar
      type: Task
      resource: urn:cascade:activity:update_calendar
      parameters:
        employee_id: $.context.employee_id
        leave_dates: $.state.leave_dates
 
  next: Complete

What it does:

Executes 3 activities simultaneously (not sequentially)
All 3 complete before moving to next
Ideal for: sending notifications, updating multiple systems
Execution time: ~max(SendEmail, NotifyHR, UpdateCalendar), not sum

Deploy and Test

1. Deploy the application


cascade app apply --file leave-request-app.yaml

2. Start a workflow instance


cascade process start leave_request_flow \
  --app=hr-leave-request \
  --input='{"employee_id": "emp-123"}'

3. Monitor execution


cascade process inspect <instance-id> --app=hr-leave-request

4. Check logs


cascade logs --app=hr-leave-request --instance=<instance-id>

Next Steps

You now understand:

✅ HumanTask (user input)
✅ Choice (conditional routing)
✅ EvaluatePolicy (business rules)
✅ Task (execute activities)
✅ Parallel (concurrent execution)

Learn More

Core Concepts - Understand CDL, activities, policies
Architecture Guide - How the system works
Policy Authoring - Write OPA/DMN policies
Workflow Development - Advanced patterns
Examples - More real-world workflows

Ready to dive deeper? Continue with Core Concepts 🚀