Expose the current step's status to SEL for conditional branching

maestro-engine/src/main/java/com/netflix/maestro/engine/eval/MaestroParamExtension.java

@@ -535,6 +535,8 @@ private Object fromStep(String fieldName) {
             stepInstanceAttributes.getType(), stepInstanceAttributes.getSubType());
       case Constants.STEP_ERROR_RETRIES_PARAM:
         return stepInstanceAttributes.getStepRetry().getErrorRetries();
+      case Constants.STEP_STATUS_PARAM:
+        return stepInstanceAttributes.getStatus().name();
       default:
         throw new MaestroValidationException(
             "Invalid field name [%s] for getFromStep call", fieldName);

maestro-engine/src/main/java/com/netflix/maestro/engine/eval/StepInstanceAttributes.java

@@ -35,6 +35,7 @@ class StepInstanceAttributes {
   private final String stepInstanceUuid;
   private final StepInstance.StepRetry stepRetry;
   private final SignalDependencies signalDependencies;
+  private final StepInstance.Status status;
 
   static StepInstanceAttributes from(StepRuntimeSummary summary) {
     return StepInstanceAttributes.builder()
@@ -46,6 +47,7 @@ static StepInstanceAttributes from(StepRuntimeSummary summary) {
         .stepInstanceUuid(summary.getStepInstanceUuid())
         .stepRetry(summary.getStepRetry())
         .signalDependencies(summary.getSignalDependencies())
+        .status(summary.getRuntimeState().getStatus())
         .build();
   }
 }

maestro-engine/src/test/java/com/netflix/maestro/engine/eval/MaestroParamExtensionTest.java

@@ -35,6 +35,7 @@
 import com.netflix.maestro.models.initiator.SignalInitiator;
 import com.netflix.maestro.models.initiator.SubworkflowInitiator;
 import com.netflix.maestro.models.instance.StepInstance;
+import com.netflix.maestro.models.instance.StepRuntimeState;
 import com.netflix.maestro.models.parameter.LongParameter;
 import com.netflix.maestro.models.parameter.MapParameter;
 import com.netflix.maestro.models.parameter.ParamType;
@@ -397,6 +398,29 @@ public void testGetFromCurrentStep() {
     assertEquals(
         StepType.NOTEBOOK.toString(), paramExtension.getFromStep(Constants.STEP_TYPE_INFO_PARAM));
     assertEquals(0L, paramExtension.getFromStep(Constants.STEP_ERROR_RETRIES_PARAM));
+    assertEquals(
+        StepInstance.Status.NOT_CREATED.name(),
+        paramExtension.getFromStep(Constants.STEP_STATUS_PARAM));
+  }
+
+  @Test
+  public void testGetStatusFromCurrentStep() {
+    StepRuntimeState runtimeState = new StepRuntimeState();
+    runtimeState.setStatus(StepInstance.Status.COMPLETED_WITH_ERROR);
+    StepRuntimeSummary summary =
+        StepRuntimeSummary.builder()
+            .stepId("step-123")
+            .type(StepType.NOTEBOOK)
+            .stepRetry(StepInstance.StepRetry.from(null))
+            .runtimeState(runtimeState)
+            .build();
+    when(instanceWrapper.isWorkflowParam()).thenReturn(false);
+    when(instanceWrapper.getStepInstanceAttributes())
+        .thenReturn(StepInstanceAttributes.from(summary));
+
+    assertEquals(
+        StepInstance.Status.COMPLETED_WITH_ERROR.name(),
+        paramExtension.getFromStep(Constants.STEP_STATUS_PARAM));
   }
 
   @Test

netflix-sel/docs/lang-guide/class-function.md

@@ -185,6 +185,18 @@ return params.getFromStep('step1', 'MAESTRO_STEP_STATUS');    // returns the sta
 return params.getFromStep('step1', 'MAESTRO_STEP_END_TIME');    // returns the end time of upstream step1.
 ```
 
+* `Object getFromStep(String)`
+
+Returns a field of the current step instead of an upstream one. Useful in a step transition condition,
+which is evaluated in the context of the step it is attached to, to branch on how that step ended.
+```sel
+return params.getFromStep('MAESTRO_STEP_STATUS');    // returns the status of the current step.
+
+return params.getFromStep('MAESTRO_STEP_STATUS') == 'COMPLETED_WITH_ERROR';    // branch taken only when the current step failed.
+
+return params.getFromStep('step_id');    // also supports step_id, step_instance_id, step_instance_uuid, step_attempt_id, step_type_info and MAESTRO_STEP_ERROR_RETRIES.
+```
+
 * `Object getFromSignal(String, String)`
 ```sel
 return params.getFromSignal('signal1', 'param1');    // returns parameter param1's value from signal1. Use it to get param from the signal triggers.