1 files changed, 44 insertions, 0 deletions
diff --git a/http-utils/src/main/java/ai/vespa/util/http/hc4/retry/DelaySupplier.java b/http-utils/src/main/java/ai/vespa/util/http/hc4/retry/DelaySupplier.java
new file mode 100644
index 00000000000..b202966c412
--- /dev/null
+++ b/http-utils/src/main/java/ai/vespa/util/http/hc4/retry/DelaySupplier.java
@@ -0,0 +1,44 @@
+// Copyright 2020 Oath Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package ai.vespa.util.http.hc4.retry;
+
+import java.time.Duration;
+
+/**
+ * An abstraction that calculates the next delay based on the current retry count.
+ *
+ * @author bjorncs
+ */
+@FunctionalInterface
+interface DelaySupplier {
+    Duration getDelay(int executionCount);
+
+    class Fixed implements DelaySupplier {
+        private final Duration delay;
+
+        Fixed(Duration delay) {
+            this.delay = delay;
+        }
+
+        @Override
+        public Duration getDelay(int executionCount) { return delay; }
+    }
+
+    class Exponential implements DelaySupplier {
+        private final Duration startDelay;
+        private final Duration maxDelay;
+
+        Exponential(Duration startDelay, Duration maxDelay) {
+            this.startDelay = startDelay;
+            this.maxDelay = maxDelay;
+        }
+
+        @Override
+        public Duration getDelay(int executionCount) {
+            Duration nextDelay = startDelay;
+            for (int i = 1; i < executionCount; ++i) {
+                nextDelay = nextDelay.multipliedBy(2);
+            }
+            return maxDelay.compareTo(nextDelay) > 0 ? nextDelay : maxDelay;
+        }
+    }
+}