From 7a779676af79c5d99749b86f3bfec794b28f6f34 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juha=20Syrj=C3=A4l=C3=A4?= <juha.syrjala@gmail.com>
Date: Wed, 22 Oct 2014 22:18:25 +0300
Subject: [PATCH] Fix binary backoff calculation for error transition delay.

---
 .../workflow/definition/WorkflowSettings.java | 15 ++++++--
 .../definition/WorkflowSettingsTest.java      | 34 +++++++++++++++++--
 2 files changed, 44 insertions(+), 5 deletions(-)

diff --git a/nflow-engine/src/main/java/com/nitorcreations/nflow/engine/workflow/definition/WorkflowSettings.java b/nflow-engine/src/main/java/com/nitorcreations/nflow/engine/workflow/definition/WorkflowSettings.java
index 1100eacd4..883ebcb2f 100644
--- a/nflow-engine/src/main/java/com/nitorcreations/nflow/engine/workflow/definition/WorkflowSettings.java
+++ b/nflow-engine/src/main/java/com/nitorcreations/nflow/engine/workflow/definition/WorkflowSettings.java
@@ -1,5 +1,6 @@
 package com.nitorcreations.nflow.engine.workflow.definition;
 
+import static java.lang.Math.max;
 import static java.lang.Math.min;
 import static java.util.concurrent.TimeUnit.DAYS;
 import static java.util.concurrent.TimeUnit.MINUTES;
@@ -9,6 +10,8 @@
 import org.joda.time.DateTime;
 import org.springframework.core.env.Environment;
 
+import java.math.BigInteger;
+
 /**
  * Configuration for the workflow execution.
  */
@@ -144,7 +147,7 @@ public WorkflowSettings build() {
    * @return Next activation time.
    */
   public DateTime getErrorTransitionActivation(int retryCount) {
-    return now().plusMillis(calculateBinaryBackoffDelay(retryCount + 1, minErrorTransitionDelay, maxErrorTransitionDelay));
+    return now().plus(calculateBinaryBackoffDelay(retryCount + 1, minErrorTransitionDelay, maxErrorTransitionDelay));
   }
 
   /**
@@ -158,8 +161,14 @@ public DateTime getErrorTransitionActivation(int retryCount) {
    *          Maximum retry delay.
    * @return Delay in milliseconds.
    */
-  protected int calculateBinaryBackoffDelay(int retryCount, int minDelay, int maxDelay) {
-    return min(minDelay * (1 << retryCount), maxDelay);
+  protected long calculateBinaryBackoffDelay(int retryCount, long minDelay, long maxDelay) {
+    BigInteger delay = BigInteger.valueOf(minDelay).multiply(BigInteger.valueOf(2).pow(retryCount));
+    if(!BigInteger.valueOf(delay.longValue()).equals(delay)) {
+      // got overflow in delay calculation
+      // Java 1.8 has delay.longValueExact()
+      return maxDelay;
+    }
+    return max(minDelay, min(delay.longValue(), maxDelay));
   }
 
   /**
diff --git a/nflow-engine/src/test/java/com/nitorcreations/nflow/engine/workflow/definition/WorkflowSettingsTest.java b/nflow-engine/src/test/java/com/nitorcreations/nflow/engine/workflow/definition/WorkflowSettingsTest.java
index 5094d493b..4bb2816eb 100644
--- a/nflow-engine/src/test/java/com/nitorcreations/nflow/engine/workflow/definition/WorkflowSettingsTest.java
+++ b/nflow-engine/src/test/java/com/nitorcreations/nflow/engine/workflow/definition/WorkflowSettingsTest.java
@@ -6,12 +6,27 @@
 import static org.joda.time.DateTimeUtils.currentTimeMillis;
 import static org.junit.Assert.assertThat;
 
+import org.joda.time.DateTime;
+import org.joda.time.DateTimeUtils;
+import org.junit.After;
+import org.junit.Before;
 import org.junit.Test;
 
-
 public class WorkflowSettingsTest {
+  DateTime now = new DateTime(2014, 10, 22, 20, 44, 0);
+
+  @Before
+  public void setup() {
+    DateTimeUtils.setCurrentMillisFixed(now.getMillis());
+  }
+
+  @After
+  public void teardown() {
+    DateTimeUtils.setCurrentMillisSystem();
+  }
+
   @Test
-  public void verifyConsantDefaultValues() {
+  public void verifyConstantDefaultValues() {
     WorkflowSettings s = new WorkflowSettings.Builder().build();
     assertThat(s.immediateTransitionDelay, is(0));
     assertThat(s.shortTransitionDelay, is(30000));
@@ -19,4 +34,19 @@ public void verifyConsantDefaultValues() {
     assertThat(delta, greaterThanOrEqualTo(-1000L));
     assertThat(delta, lessThanOrEqualTo(0L));
   }
+
+  @Test
+  public void errorTransitionDelayIsBetweenMinAndMaxDelay() {
+    int maxDelay = 1_000_000;
+    int minDelay = 1000;
+    WorkflowSettings s = new WorkflowSettings.Builder().setMinErrorTransitionDelay(minDelay).setMaxErrorTransitionDelay(maxDelay).build();
+    long prevDelay = 0;
+    for(int retryCount = 0 ; retryCount < 100 ; retryCount++) {
+      long delay  = s.getErrorTransitionActivation(retryCount).getMillis() - now.getMillis();
+      assertThat(delay, greaterThanOrEqualTo((long)minDelay));
+      assertThat(delay, lessThanOrEqualTo((long)maxDelay));
+      assertThat(delay, greaterThanOrEqualTo(prevDelay));
+      prevDelay = delay;
+    }
+  }
 }