diff --git a/src/cluster/Backend.cc b/src/cluster/Backend.cc
index 177997238b..e46d989476 100644
--- a/src/cluster/Backend.cc
+++ b/src/cluster/Backend.cc
@@ -10,8 +10,8 @@
 #include "zeek/Func.h"
 #include "zeek/Reporter.h"
 #include "zeek/Type.h"
+#include "zeek/cluster/OnLoop.h"
 #include "zeek/cluster/Serializer.h"
-#include "zeek/iosource/Manager.h"
 #include "zeek/logging/Manager.h"
 #include "zeek/util.h"
 
@@ -158,63 +158,26 @@ bool ThreadedBackend::ProcessBackendMessage(int tag, detail::byte_buffer_span pa
     return DoProcessBackendMessage(tag, payload);
 }
 
-namespace {
-
-bool register_io_source(zeek::iosource::IOSource* src, int fd, bool dont_count) {
-    constexpr bool manage_lifetime = true;
-
-    zeek::iosource_mgr->Register(src, dont_count, manage_lifetime);
-
-    if ( ! zeek::iosource_mgr->RegisterFd(fd, src) ) {
-        zeek::reporter->Error("Failed to register messages_flare with IO manager");
-        return false;
-    }
-
-    return true;
+ThreadedBackend::ThreadedBackend(std::unique_ptr<EventSerializer> es, std::unique_ptr<LogSerializer> ls,
+                                 std::unique_ptr<detail::EventHandlingStrategy> ehs)
+    : Backend(std::move(es), std::move(ls), std::move(ehs)) {
+    onloop = new zeek::detail::OnLoopProcess<ThreadedBackend, QueueMessages>(this, "ThreadedBackend");
+    onloop->Register(true); // Register as don't count first
 }
-} // namespace
 
 bool ThreadedBackend::DoInit() {
-    // Register as counting during DoInit() to avoid Zeek from shutting down.
-    return register_io_source(this, messages_flare.FD(), false);
-}
-
-void ThreadedBackend::DoInitPostScript() {
-    // Register non-counting after parsing scripts.
-    register_io_source(this, messages_flare.FD(), true);
+    // Have the backend count so Zeek does not terminate.
+    onloop->Register(/*dont_count=*/false);
+    return true;
 }
 
 void ThreadedBackend::QueueForProcessing(QueueMessages&& qmessages) {
-    bool fire = false;
-
-    // Enqueue under lock.
-    {
-        std::scoped_lock lock(messages_mtx);
-        fire = messages.empty();
-
-        if ( messages.empty() ) {
-            messages = std::move(qmessages);
-        }
-        else {
-            messages.reserve(messages.size() + qmessages.size());
-            for ( auto& qmsg : qmessages )
-                messages.emplace_back(std::move(qmsg));
-        }
-    }
-
-    if ( fire )
-        messages_flare.Fire();
+    onloop->QueueForProcessing(std::move(qmessages));
 }
 
-void ThreadedBackend::Process() {
-    QueueMessages to_process;
-    {
-        std::scoped_lock lock(messages_mtx);
-        to_process = std::move(messages);
-        messages_flare.Extinguish();
-        messages.clear();
-    }
+void ThreadedBackend::Process() { onloop->Process(); }
 
+void ThreadedBackend::Process(QueueMessages&& to_process) {
     for ( const auto& msg : to_process ) {
         // sonarlint wants to use std::visit. not sure...
         if ( auto* emsg = std::get_if<EventMessage>(&msg) ) {
diff --git a/src/cluster/Backend.h b/src/cluster/Backend.h
index 5953c7b8b2..2feadb89a6 100644
--- a/src/cluster/Backend.h
+++ b/src/cluster/Backend.h
@@ -5,17 +5,14 @@
 #pragma once
 
 #include <memory>
-#include <mutex>
 #include <optional>
 #include <string_view>
 #include <variant>
 
 #include "zeek/EventHandler.h"
-#include "zeek/Flare.h"
 #include "zeek/IntrusivePtr.h"
 #include "zeek/Span.h"
 #include "zeek/cluster/Serializer.h"
-#include "zeek/iosource/IOSource.h"
 #include "zeek/logging/Types.h"
 
 namespace zeek {
@@ -28,6 +25,11 @@ class Val;
 using ValPtr = IntrusivePtr<Val>;
 using ArgsSpan = Span<const ValPtr>;
 
+namespace detail {
+template<class Proc, class Work>
+class OnLoopProcess;
+}
+
 namespace cluster {
 
 namespace detail {
@@ -465,11 +467,14 @@ using QueueMessages = std::vector<QueueMessage>;
  * Support for backends that use background threads or invoke
  * callbacks on non-main threads.
  */
-class ThreadedBackend : public Backend, public zeek::iosource::IOSource {
-public:
-    using Backend::Backend;
-
+class ThreadedBackend : public Backend {
 protected:
+    /**
+     * Constructor.
+     */
+    ThreadedBackend(std::unique_ptr<EventSerializer> es, std::unique_ptr<LogSerializer> ls,
+                    std::unique_ptr<detail::EventHandlingStrategy> ehs);
+
     /**
      * To be used by implementations to enqueue messages for processing on the IO loop.
      *
@@ -479,20 +484,11 @@ protected:
      */
     void QueueForProcessing(QueueMessages&& messages);
 
-    void Process() override;
-
-    double GetNextTimeout() override { return -1; }
-
     /**
-     * The DoInitPostScript() implementation of ThreadedBackend
-     * registers itself as a non-counting IO source.
-     *
-     * Classes deriving from ThreadedBackend and providing their
-     * own DoInitPostScript() method should invoke the ThreadedBackend's
-     * implementation to register themselves as a non-counting
-     * IO source with the IO loop.
+     * Delegate to onloop->Process() to trigger processing
+     * of outstanding queued messages explicitly, if any.
      */
-    void DoInitPostScript() override;
+    void Process();
 
     /**
      * The default DoInit() implementation of ThreadedBackend
@@ -518,10 +514,16 @@ private:
      */
     virtual bool DoProcessBackendMessage(int tag, detail::byte_buffer_span payload) { return false; };
 
+    /**
+     * Hook method for OnLooProcess.
+     */
+    void Process(QueueMessages&& messages);
+
+    // Allow access to Process(QueueMessages)
+    friend class zeek::detail::OnLoopProcess<ThreadedBackend, QueueMessages>;
+
     // Members used for communication with the main thread.
-    std::mutex messages_mtx;
-    std::vector<QueueMessage> messages;
-    zeek::detail::Flare messages_flare;
+    zeek::detail::OnLoopProcess<ThreadedBackend, QueueMessages>* onloop;
 };