retry: add the ability to cap the maxRetryFactor. fix left-shifts so they don't go negative.

Signed-off-by: Ken McCracken <ken.mccracken@here.com>

Author: kenmccracken

here-oauth-client/src/main/java/com/here/account/oauth2/retry/Socket5xxExponentialRandomBackoffPolicy.java

@@ -11,18 +11,25 @@ public class Socket5xxExponentialRandomBackoffPolicy implements RetryPolicy {
 
     public static final int DEFAULT_MAX_NO_RETRIES = 3;
     public static final int DEFAULT_RETRY_INTERVAL_MILLIS = 1000;
+    public static final int DEFAULT_MAX_RETRY_FACTOR = 1 << 30;
 
     private final int maxNumberOfRetries;
     private final int retryIntervalMillis;
+    private final int maxRetryFactor;
 
     public Socket5xxExponentialRandomBackoffPolicy(){
-        this.maxNumberOfRetries = DEFAULT_MAX_NO_RETRIES;
-        this.retryIntervalMillis = DEFAULT_RETRY_INTERVAL_MILLIS;
+        this(DEFAULT_MAX_NO_RETRIES, DEFAULT_RETRY_INTERVAL_MILLIS);
     }
 
     public Socket5xxExponentialRandomBackoffPolicy(int maxNumberOfRetries, int retryIntervalMillis){
+        this(maxNumberOfRetries, retryIntervalMillis, DEFAULT_MAX_RETRY_FACTOR);
+    }
+
+    public Socket5xxExponentialRandomBackoffPolicy(int maxNumberOfRetries, int retryIntervalMillis,
+                                                   int maxRetryFactor) {
         this.maxNumberOfRetries = maxNumberOfRetries;
         this.retryIntervalMillis = retryIntervalMillis;
+        this.maxRetryFactor = maxRetryFactor;
     }
 
     @Override
@@ -36,7 +43,8 @@ public boolean shouldRetry(RetryContext retryContext) {
 
     @Override
     public int getNextRetryIntervalMillis(RetryContext retryContext){
-        int factor = 1 << (retryContext.getRetryCount());
+        int retryCount = retryContext.getRetryCount();
+        int factor = Math.min(1 << (Math.min(retryCount, 30)), maxRetryFactor);
         return  retryIntervalMillis * ThreadLocalRandom.current().nextInt(factor);
     }
 }

here-oauth-client/src/test/java/com/here/account/oauth2/retry/Socket5xxExponentialRandomBackoffPolicyTest.java

@@ -0,0 +1,44 @@
+package com.here.account.oauth2.retry;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.mockito.Mockito;
+import java.net.SocketTimeoutException;
+import com.here.account.http.HttpProvider;
+
+import static org.junit.Assert.assertTrue;
+
+public class Socket5xxExponentialRandomBackoffPolicyTest {
+
+    private Socket5xxExponentialRandomBackoffPolicy socket5xxExponentialRandomBackoffPolicy;
+    int maxNumberOfRetries = Integer.MAX_VALUE;
+    int retryIntervalMillis = 500;
+    int maxRetryFactor = 5;
+
+    @Before
+    public void setUp() {
+        this.socket5xxExponentialRandomBackoffPolicy =
+                new Socket5xxExponentialRandomBackoffPolicy( maxNumberOfRetries,  retryIntervalMillis,
+                        maxRetryFactor);
+    }
+
+    @Test
+    public void test_shouldRetry() {
+        HttpProvider.HttpResponse httpResponse = Mockito.mock(HttpProvider.HttpResponse.class);
+        Mockito.when(httpResponse.getStatusCode()).thenReturn(503);
+        Exception lastException = Mockito.mock(SocketTimeoutException.class);
+        RetryContext retryContext = new RetryContext();
+        retryContext.setLastRetryResponse(httpResponse);
+        retryContext.setLastException(lastException);
+        final int maxRetryIntervalMillis = maxRetryFactor * retryIntervalMillis;
+        for (int i = 0; i < 1000; i++) {
+            retryContext.incrementRetryCount();
+            assertTrue("shouldRetry should have been true",
+                    socket5xxExponentialRandomBackoffPolicy.shouldRetry(retryContext));
+            int nextRetryIntervalMillis = socket5xxExponentialRandomBackoffPolicy.getNextRetryIntervalMillis(retryContext);
+            assertTrue("unexpected nextRetryIntervalMillis "
+                            + nextRetryIntervalMillis + ", should be >= 0 and <= " + maxRetryIntervalMillis,
+                    nextRetryIntervalMillis >= 0 && nextRetryIntervalMillis <= maxRetryIntervalMillis);
+        }
+    }
+}