Skip to main content

Documentation Index

Fetch the complete documentation index at: https://docs.dualship.run/llms.txt

Use this file to discover all available pages before exploring further.

The try node provides structured error handling, similar to try/catch/finally in programming languages. Use it to gracefully handle errors and ensure cleanup code runs.

​
Configuration

{
  "id": "safe_api_call",
  "type": "try",
  "config": {
    "try": ["fetch_data", "process_data"],
    "catch": ["handle_error"],
    "finally": ["cleanup"]
  }
}

​
Config Fields

FieldTypeRequiredDescription
trystring[]YesNode IDs to execute (at least one required)
catchstring[]NoNode IDs to execute if an error occurs
finallystring[]NoNode IDs that always execute

​
Execution Flow

      try block
          |
    +-----+-----+
    |           |
 success      error
    |           |
    |        catch block
    |           |
    +-----+-----+
          |
    finally block
          |
       continue
  1. Execute all nodes in try
  2. If error occurs, execute catch nodes
  3. Always execute finally nodes
  4. Continue with flow

​
Output

​
On Success

{
  "success": true,
  "result": { ... },
  "error": null,
  "failed_node": null
}

​
On Error

{
  "success": false,
  "result": null,
  "error": "connection timeout",
  "failed_node": "fetch_data"
}
FieldTypeDescription
successbooleanWhether try block completed without error
resultanyOutput from last successful node
errorstringError message if failed
failed_nodestringID of node that failed

​
Error Context

In the catch block, error information is available:
ExpressionDescription
{{error.message}}The error message
{{error.node}}ID of the node that failed
{{error.type}}Type of error

​
Examples

​
Basic Error Handling

{
  "id": "fetch_with_fallback",
  "type": "try",
  "config": {
    "try": ["fetch_from_primary_api"],
    "catch": ["fetch_from_backup_api"]
  }
}

​
With Cleanup

{
  "id": "transaction",
  "type": "try",
  "config": {
    "try": ["start_transaction", "process_payment", "commit"],
    "catch": ["rollback"],
    "finally": ["release_lock"]
  }
}

​
Logging Errors

[
  {
    "id": "safe_operation",
    "type": "try",
    "config": {
      "try": ["risky_operation"],
      "catch": ["log_error", "set_fallback"],
      "finally": ["track_metrics"]
    }
  },
  {
    "id": "log_error",
    "type": "set",
    "config": {
      "key": "error_log",
      "value": {
        "message": "{{error.message}}",
        "node": "{{error.node}}",
        "timestamp": "{{now}}"
      }
    }
  },
  {
    "id": "set_fallback",
    "type": "set",
    "config": {
      "key": "result",
      "value": {
        "data": [],
        "source": "fallback",
        "error": "{{error.message}}"
      }
    }
  }
]

​
API Call with Fallback Response

[
  {
    "id": "try_fetch",
    "type": "try",
    "config": {
      "try": ["fetch_user_data", "transform_data"],
      "catch": ["set_default_data"]
    }
  },
  {
    "id": "fetch_user_data",
    "type": "http",
    "config": {
      "url": "https://api.example.com/users/{{user_id}}",
      "timeout": 5000
    }
  },
  {
    "id": "set_default_data",
    "type": "set",
    "config": {
      "key": "user_data",
      "value": {
        "id": "{{user_id}}",
        "name": "Unknown",
        "loaded_from": "fallback"
      }
    }
  }
]

​
Conditional Error Response

[
  {
    "id": "try_operation",
    "type": "try",
    "config": {
      "try": ["validate", "process"],
      "catch": ["set_error"]
    }
  },
  {
    "id": "set_error",
    "type": "set",
    "config": {
      "key": "operation_error",
      "value": {
        "failed": true,
        "message": "{{error.message}}",
        "recoverable": true
      }
    }
  },
  {
    "id": "check_error",
    "type": "condition",
    "config": {
      "conditions": [
        {
          "if": "{{operation_error.failed}} == true",
          "then": ["error_response"]
        }
      ],
      "else": ["success_response"]
    }
  }
]

​
Nested Try Blocks

Try nodes can be nested for granular error handling: 
[
  {
    "id": "outer_try",
    "type": "try",
    "config": {
      "try": ["inner_try", "final_step"],
      "catch": ["catastrophic_error"]
    }
  },
  {
    "id": "inner_try",
    "type": "try",
    "config": {
      "try": ["risky_step"],
      "catch": ["recover_from_risky"]
    }
  }
]

​
Use Cases

​
API Resilience

Wrap external API calls to handle failures gracefully: 
{
  "try": ["call_external_api"],
  "catch": ["use_cached_data"],
  "finally": ["log_attempt"]
}

​
Transaction Safety

Ensure rollback happens if processing fails: 
{
  "try": ["begin_tx", "update_db", "commit_tx"],
  "catch": ["rollback_tx", "log_failure"]
}

​
Resource Cleanup

Always release resources regardless of success/failure: 
{
  "try": ["acquire_lock", "do_work"],
  "finally": ["release_lock"]
}

​
Error Propagation

  • If catch handles the error, the flow continues normally
  • If catch itself fails, the error propagates up
  • finally always runs, even if catch fails