From d5ac709986139fb4e4ad1b3fb0e33b3511a93486 Mon Sep 17 00:00:00 2001
From: Hans Ott <hansott@hotmail.be>
Date: Wed, 19 Aug 2026 17:20:15 +0200
Subject: [PATCH] Skip SSE config updated events if they arrive too fast

---
 .../agent_api/background/RealtimeSSETask.java | 21 ++++++++++++++++++-
 .../java/background/RealtimeSSETaskTest.java  | 16 ++++++++++++--
 2 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/agent_api/src/main/java/dev/aikido/agent_api/background/RealtimeSSETask.java b/agent_api/src/main/java/dev/aikido/agent_api/background/RealtimeSSETask.java
index 30c67618..a82e841d 100644
--- a/agent_api/src/main/java/dev/aikido/agent_api/background/RealtimeSSETask.java
+++ b/agent_api/src/main/java/dev/aikido/agent_api/background/RealtimeSSETask.java
@@ -12,12 +12,14 @@
 import dev.aikido.agent_api.storage.ServiceConfigStore;
 
 import java.util.Optional;
+import java.util.concurrent.TimeUnit;
 
 public class RealtimeSSETask extends Thread {
     private static final Logger logger = LogManager.getLogger(RealtimeSSETask.class);
     private final RealtimeSSEAPI realtimeSSEApi;
     private final ReportingApiHTTP reportingApi;
     private Optional<Long> configLastUpdatedAt;
+    private Optional<Long> lastConfigRefreshStartedAt = Optional.empty();
 
     public RealtimeSSETask(RealtimeSSEAPI realtimeSSEApi, ReportingApiHTTP reportingApi) {
         super("RealtimeSSETask");
@@ -32,7 +34,7 @@ public void run() {
         realtimeSSEApi.listen(this::onEvent);
     }
 
-    public void onEvent(SSEParser.Event event) {
+    public synchronized void onEvent(SSEParser.Event event) {
         logger.trace("SSE event received: %s", event.event());
         if (!"config-updated".equals(event.event())) {
             return;
@@ -51,6 +53,11 @@ public void onEvent(SSEParser.Event event) {
             return;
         }
 
+        if (configUpdateArrivedTooFast()) {
+            logger.debug("Ignoring SSE config-updated event during refresh throttle");
+            return;
+        }
+
         Optional<APIResponse> newConfig = reportingApi.fetchNewConfig();
         if (newConfig.isEmpty()) {
             logger.debug("Failed to fetch config after SSE event");
@@ -66,4 +73,16 @@ public void onEvent(SSEParser.Event event) {
 
         logger.debug("Config updated via SSE");
     }
+
+    private boolean configUpdateArrivedTooFast() {
+        long now = System.nanoTime();
+        if (lastConfigRefreshStartedAt.isPresent()) {
+            if (now - lastConfigRefreshStartedAt.get() < TimeUnit.SECONDS.toNanos(9)) {
+                return true;
+            }
+        }
+
+        lastConfigRefreshStartedAt = Optional.of(now);
+        return false;
+    }
 }
diff --git a/agent_api/src/test/java/background/RealtimeSSETaskTest.java b/agent_api/src/test/java/background/RealtimeSSETaskTest.java
index a0375e0e..8ad84972 100644
--- a/agent_api/src/test/java/background/RealtimeSSETaskTest.java
+++ b/agent_api/src/test/java/background/RealtimeSSETaskTest.java
@@ -84,7 +84,7 @@ public void testHandlesFetchFailureGracefully() {
     }
 
     @Test
-    public void testRepeatedEventAfterFetchFailure() {
+    public void testThrottlesRepeatedEventAfterFetchFailure() {
         when(reportingApi.fetchNewConfig())
                 .thenReturn(Optional.empty())
                 .thenReturn(Optional.of(sampleConfig(200)));
@@ -94,7 +94,19 @@ public void testRepeatedEventAfterFetchFailure() {
         task.onEvent(event);
         task.onEvent(event);
 
-        verify(reportingApi, times(2)).fetchNewConfig();
+        verify(reportingApi, times(1)).fetchNewConfig();
+        verify(reportingApi, never()).fetchBlockedLists();
+    }
+
+    @Test
+    public void testThrottlesNewerEvents() {
+        when(reportingApi.fetchNewConfig()).thenReturn(Optional.of(sampleConfig(200)));
+        when(reportingApi.fetchBlockedLists()).thenReturn(Optional.empty());
+
+        task.onEvent(new SSEParser.Event("config-updated", "{\"configUpdatedAt\":200}"));
+        task.onEvent(new SSEParser.Event("config-updated", "{\"configUpdatedAt\":300}"));
+
+        verify(reportingApi, times(1)).fetchNewConfig();
         verify(reportingApi, times(1)).fetchBlockedLists();
     }