1 files changed, 60 insertions, 0 deletions
diff --git a/framework/src/onos/utils/misc/src/main/java/org/onlab/util/RetryingFunction.java b/framework/src/onos/utils/misc/src/main/java/org/onlab/util/RetryingFunction.java
new file mode 100644
index 00000000..484e236f
--- /dev/null
+++ b/framework/src/onos/utils/misc/src/main/java/org/onlab/util/RetryingFunction.java
@@ -0,0 +1,60 @@
+/*
+ * Copyright 2015 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onlab.util;
+
+import java.util.function.Function;
+
+import com.google.common.base.Throwables;
+
+/**
+ * Function that retries execution on failure.
+ *
+ * @param <U> input type
+ * @param <V> output type
+ */
+public class RetryingFunction<U, V> implements Function<U, V> {
+
+    private final Function<U, V> baseFunction;
+    private final Class<? extends Throwable> exceptionClass;
+    private final int maxRetries;
+    private final int maxDelayBetweenRetries;
+
+    public RetryingFunction(Function<U, V> baseFunction,
+            Class<? extends Throwable> exceptionClass,
+            int maxRetries,
+            int maxDelayBetweenRetries) {
+        this.baseFunction = baseFunction;
+        this.exceptionClass = exceptionClass;
+        this.maxRetries = maxRetries;
+        this.maxDelayBetweenRetries = maxDelayBetweenRetries;
+    }
+
+    @Override
+    public V apply(U input) {
+        int retryAttempts = 0;
+        while (true) {
+            try {
+                return baseFunction.apply(input);
+            } catch (Throwable t) {
+                if (!exceptionClass.isAssignableFrom(t.getClass()) || retryAttempts == maxRetries) {
+                    Throwables.propagate(t);
+                }
+                Tools.randomDelay(maxDelayBetweenRetries);
+                retryAttempts++;
+            }
+        }
+    }
+}