Revert "Remove HostLivenessTracker"

1 files changed, 24 insertions, 0 deletions

diff --git a/config-provisioning/src/main/java/com/yahoo/config/provision/HostLivenessTracker.java b/config-provisioning/src/main/java/com/yahoo/config/provision/HostLivenessTracker.java
new file mode 100644
index 00000000000..f3326ec2bc8
--- /dev/null
+++ b/config-provisioning/src/main/java/com/yahoo/config/provision/HostLivenessTracker.java
@@ -0,0 +1,24 @@
+// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.config.provision;
+
+import java.time.Instant;
+import java.util.Optional;
+
+/**
+ * Instances of this are used to keep track of (notify and query)
+ * which hosts are currently connected to the config system.
+ * 
+ * @author bratseth
+ */
+public interface HostLivenessTracker {
+
+    /** Called each time a config request is received from a client */
+    void receivedRequestFrom(String hostname);
+
+    /** 
+     * Returns the epoch timestamp of the last request received from the given hostname,
+     * or empty if there is no memory of this host making a request
+     */
+    Optional<Instant> lastRequestFrom(String hostname);
+
+}