fix(azure-iot-common): Fix for #338: Exp backoff retry formula

Azure · Jul 27, 2018 · dd36fbe · dd36fbe
1 parent 08f541f
commit dd36fbe
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Showing 2 changed files with 10 additions and 10 deletions.
diff --git a/common/core/src/retry_policy.ts b/common/core/src/retry_policy.ts
@@ -134,7 +134,7 @@ export class ExponentialBackOffWithJitter implements RetryPolicy {
       let minRandomFactor = constants.c * (1 - constants.jd);
       let maxRandomFactor = constants.c * (1 - constants.ju);
       let randomJitter = Math.random() * (maxRandomFactor - minRandomFactor);
-      return Math.min(constants.cMin + (Math.pow(retryCount - 1, 2) - 1) * randomJitter, constants.cMax);
+      return Math.min(constants.cMin + (Math.pow(2, retryCount - 1) - 1) * randomJitter, constants.cMax);
     }
   }
 

diff --git a/common/core/test/_retry_policy_test.js b/common/core/test/_retry_policy_test.js
@@ -38,10 +38,10 @@ describe('RetryPolicy', function () {
         Math.random.restore();
       });
 
-      it('returns \'C\' for the first retry if the first retry is not set to be immediate', function () {
+      it('returns a non-zero value for the first retry if the first retry is not set to be immediate', function () {
         sinon.stub(Math, 'random').returns(0.42);
         var policy = new ExponentialBackOffWithJitter(false);
-        assert.strictEqual(policy.nextRetryTimeout(0, false), 100);
+        assert.isAbove(policy.nextRetryTimeout(0, false), 0);
         Math.random.restore();
       });
 
@@ -59,10 +59,10 @@ describe('RetryPolicy', function () {
         ```]*/
         [
           { retryCount: 0, expected: 0 },
-          { retryCount: 1, expected: 89.5 },
-          { retryCount: 2, expected: 100 },
+          { retryCount: 1, expected: 100 },
+          { retryCount: 2, expected: 110.5 },
           { retryCount: 3, expected: 131.5 },
-          { retryCount: 10, expected: 940 },
+          { retryCount: 10, expected: 5465.5 },
           { retryCount: 42, expected: 10000 }
         ].forEach(function (testConfig) {
           assert.strictEqual(policy.nextRetryTimeout(testConfig.retryCount, false), testConfig.expected);
@@ -77,11 +77,11 @@ describe('RetryPolicy', function () {
         jd = 0.25
         ```]*/
         [
-          { retryCount: 0, expected: 10000 },
-          { retryCount: 1, expected: 9475 },
-          { retryCount: 2, expected: 10000 },
+          { retryCount: 0, expected: 9737.5 },
+          { retryCount: 1, expected: 10000 },
+          { retryCount: 2, expected: 10525 },
           { retryCount: 3, expected: 11575 },
-          { retryCount: 10, expected: 52000 },
+          { retryCount: 10, expected: 60000 },
           { retryCount: 42, expected: 60000 }
         ].forEach(function (testConfig) {
           assert.strictEqual(policy.nextRetryTimeout(testConfig.retryCount, true), testConfig.expected);