Error Handling & Resilience

EUIX provides declarative error handling and resilience pipelines via the Resilience Plugin (euixjs/resilience) and Action Composer (euixjs/composer).

🛡️ The Try / Catch / Finally Pipeline #

You can wrap fragile operations (like network requests or complex data mutations) in declarative try/catch pipelines:

graph TD
    A["Action Dispatch"] --> B["<try> Block"]
    B --> C{"Success?"}
    C -- Yes --> D["Update State / Data"]
    C -- No --> E["<catch> Block (Fallback State / Alert)"]
    D --> F["<finally> Block (Clean up spinners / loading)"]
    E --> F

graph TD
    A["Action Dispatch"] --> B["<try> Block"]
    B --> C{"Success?"}
    C -- Yes --> D["Update State / Data"]
    C -- No --> E["<catch> Block (Fallback State / Alert)"]
    D --> F["<finally> Block (Clean up spinners / loading)"]
    E --> F

<step action="TRY">
  <try>
    <step action="XHR">
      <url>https://api.example.com/sensitive-data</url>
      <target>data.payload</target>
      <timeout ms="4000" />
      <retry max="3" backoff="exponential" />
    </step>
  </try>
  
  <catch>
    <step action="SET_STATE">
      <path>data.errorMessage</path>
      <value>Unable to retrieve data. Please try again later.</value>
    </step>
  </catch>
  
  <finally>
    <step action="SET_STATE">
      <path>data.isLoading</path>
      <value>false</value>
    </step>
  </finally>
</step>

⚙️ Resilience Capabilities #

• Timeouts (<timeout ms="5000" />): Automatically aborts long-hanging network requests or asynchronous tasks.
• Exponential Retry (<retry max="3" backoff="exponential" />): Retries failed network requests with progressive delay increments.
• Circuit Breaker: Prevents repeated request flooding when a remote service is continuously returning 5xx errors.

🧭 Next Step #

Learn about using JavaScript as an escape hatch in RUN_SCRIPT & Sandboxing.