Add Broker::forward() function

This enables explicit forwarding of events matching a given topic
prefix.  Even if a receiving node has an event handler, it will not
be raised if the event was sent along a topic that matches a previous
call to Broker::forward().

scripts/base/frameworks/broker/main.bro

@@ -285,11 +285,25 @@ export {
 	## (except during :bro:see:`bro_init`).
 	##
 	## topic_prefix: a prefix previously supplied to a successful call to
-	##               :bro:see:`Broker::subscribe`.
+	##               :bro:see:`Broker::subscribe` or :bro:see:`Broker::forward`.
 	##
 	## Returns: true if interest in the topic prefix is no longer advertised.
 	global unsubscribe: function(topic_prefix: string): bool;
 
+	## Register a topic prefix subscription for events that should only be
+	## forwarded to any subscribing peers and not raise any event handlers
+	## on the receiving/forwarding node.  i.e. it's the same as
+	## :bro:see:`Broker::subscribe` except matching events are not raised
+	## on the receiver, just forwarded.  Use :bro:see:`Broker::unsubscribe`
+	## with the same argument to undo this operation.
+	##
+	## topic_prefix: a prefix to match against remote message topics.
+	##               e.g. an empty prefix matches everything and "a" matches
+	##               "alice" and "amy" but not "bob".
+	##
+	## Returns: true if a new event forwarding/subscription is now registered.
+	global forward: function(topic_prefix: string): bool;
+
 	## Automatically send an event to any interested peers whenever it is
 	## locally dispatched. (For example, using "event my_event(...);" in a
 	## script.)
@@ -377,6 +391,11 @@ function subscribe(topic_prefix: string): bool
 	return __subscribe(topic_prefix);
 	}
 
+function forward(topic_prefix: string): bool
+	{
+	return __forward(topic_prefix);
+	}
+
 function unsubscribe(topic_prefix: string): bool
 	{
 	return __unsubscribe(topic_prefix);

src/broker/Manager.cc

@@ -2,6 +2,7 @@
 #include <broker/broker.hh>
 #include <broker/bro.hh>
 #include <cstdio>
+#include <cstring>
 #include <unistd.h>
 
 #include "Manager.h"
@@ -787,8 +788,28 @@ bool Manager::Subscribe(const string& topic_prefix)
 	return true;
 	}
 
+bool Manager::Forward(string topic_prefix)
+	{
+	for ( auto i = 0u; i < forwarded_prefixes.size(); ++i )
+		if ( forwarded_prefixes[i] == topic_prefix )
+			return false;
+
+	DBG_LOG(DBG_BROKER, "Forwarding topic prefix %s", topic_prefix.c_str());
+	Subscribe(topic_prefix);
+	forwarded_prefixes.emplace_back(std::move(topic_prefix));
+	return true;
+	}
+
 bool Manager::Unsubscribe(const string& topic_prefix)
 	{
+	for ( auto i = 0u; i < forwarded_prefixes.size(); ++i )
+		if ( forwarded_prefixes[i] == topic_prefix )
+			{
+			DBG_LOG(DBG_BROKER, "Unforwading topic prefix %s", topic_prefix.c_str());
+			forwarded_prefixes.erase(forwarded_prefixes.begin() + i);
+			break;
+			}
+
 	DBG_LOG(DBG_BROKER, "Unsubscribing from topic prefix %s", topic_prefix.c_str());
 	bstate->subscriber.remove_topic(topic_prefix, ! after_bro_init);
 	return true;
@@ -828,11 +849,11 @@ double Manager::NextTimestamp(double* local_network_time)
 	return -1;
 	}
 
-void Manager::DispatchMessage(broker::data msg)
+void Manager::DispatchMessage(const broker::topic& topic, broker::data msg)
 	{
 	switch ( broker::bro::Message::type(msg) ) {
 	case broker::bro::Message::Type::Event:
-		ProcessEvent(std::move(msg));
+		ProcessEvent(topic, std::move(msg));
 		break;
 
 	case broker::bro::Message::Type::LogCreate:
@@ -852,7 +873,7 @@ void Manager::DispatchMessage(broker::data msg)
 		broker::bro::Batch batch(std::move(msg));
 
 		for ( auto& i : batch.batch() )
-			DispatchMessage(std::move(i));
+			DispatchMessage(topic, std::move(i));
 
 		break;
 		}
@@ -900,7 +921,7 @@ void Manager::Process()
 
 		try
 			{
-			DispatchMessage(std::move(msg));
+			DispatchMessage(topic, std::move(msg));
 			}
 		catch ( std::runtime_error& e )
 			{
@@ -923,8 +944,11 @@ void Manager::Process()
 	}
 
 
-void Manager::ProcessEvent(std::string name, broker::vector args)
+void Manager::ProcessEvent(const broker::topic& topic, broker::bro::Event ev)
 	{
+	auto name = std::move(ev.name());
+	auto args = std::move(ev.args());
+
 	DBG_LOG(DBG_BROKER, "Process event: %s %s",
 			name.data(), RenderMessage(args).data());
 	++statistics.num_events_incoming;
@@ -933,6 +957,23 @@ void Manager::ProcessEvent(std::string name, broker::vector args)
 	if ( ! handler )
 		return;
 
+	auto& topic_string = topic.string();
+
+	for ( auto i = 0u; i < forwarded_prefixes.size(); ++i )
+		{
+		auto& p = forwarded_prefixes[i];
+
+		if ( p.size() > topic_string.size() )
+			continue;
+
+		if ( strncmp(p.data(), topic_string.data(), p.size()) != 0 )
+			continue;
+
+		DBG_LOG(DBG_BROKER, "Skip processing of forwarded event: %s %s",
+		        name.data(), RenderMessage(args).data());
+		return;
+		}
+
 	auto arg_types = handler->FType(false)->ArgTypes()->Types();
 
 	if ( static_cast<size_t>(arg_types->length()) != args.size() )
@@ -969,11 +1010,6 @@ void Manager::ProcessEvent(std::string name, broker::vector args)
 		delete_vals(vl);
 	}
 
-void Manager::ProcessEvent(broker::bro::Event ev)
-	{
-	ProcessEvent(std::move(ev.name()), std::move(ev.args()));
-	}
-
 bool bro_broker::Manager::ProcessLogCreate(broker::bro::LogCreate lc)
 	{
 	DBG_LOG(DBG_BROKER, "Received log-create: %s", RenderMessage(lc).c_str());

src/broker/Manager.h

@@ -224,10 +224,21 @@ public:
 	 */
 	bool Subscribe(const std::string& topic_prefix);
 
+	/**
+	 * Register interest in peer event messages that use a certain topic prefix,
+	 * but that should not be raised locally, just forwarded to any subscribing
+	 * peers.
+	 * @param topic_prefix a prefix to match against remote message topics.
+	 * e.g. an empty prefix will match everything and "a" will match "alice"
+	 * and "amy" but not "bob".
+	 * @return true if it's a new event forward/subscription and it is now registered.
+	 */
+	bool Forward(std::string topic_prefix);
+
 	/**
 	 * Unregister interest in peer event messages.
 	 * @param topic_prefix a prefix previously supplied to a successful call
-	 * to bro_broker::Manager::Subscribe().
+	 * to bro_broker::Manager::Subscribe() or bro_broker::Manager::Forward().
 	 * @return true if interest in topic prefix is no longer advertised.
 	 */
 	bool Unsubscribe(const std::string& topic_prefix);
@@ -311,9 +322,8 @@ public:
 
 private:
 
-	void DispatchMessage(broker::data msg);
-	void ProcessEvent(std::string name, broker::vector args);
-	void ProcessEvent(broker::bro::Event ev);
+	void DispatchMessage(const broker::topic& topic, broker::data msg);
+	void ProcessEvent(const broker::topic& topic, broker::bro::Event ev);
 	bool ProcessLogCreate(broker::bro::LogCreate lc);
 	bool ProcessLogWrite(broker::bro::LogWrite lw);
 	bool ProcessIdentifierUpdate(broker::bro::IdentifierUpdate iu);
@@ -364,6 +374,7 @@ private:
 	std::unordered_map<std::string, StoreHandleVal*> data_stores;
 	std::unordered_map<query_id, StoreQueryCallback*,
 	                   query_id_hasher> pending_queries;
+	std::vector<std::string> forwarded_prefixes;
 
 	Stats statistics;
 

src/broker/messaging.bif

@@ -144,6 +144,13 @@ function Broker::__subscribe%(topic_prefix: string%): bool
 	return new Val(rval, TYPE_BOOL);
 	%}
 
+function Broker::__forward%(topic_prefix: string%): bool
+	%{
+	bro_broker::Manager::ScriptScopeGuard ssg;
+	auto rval = broker_mgr->Forward(topic_prefix->CheckString());
+	return new Val(rval, TYPE_BOOL);
+	%}
+
 function Broker::__unsubscribe%(topic_prefix: string%): bool
 	%{
 	bro_broker::Manager::ScriptScopeGuard ssg;

testing/btest/Baseline/scripts.base.frameworks.cluster.forwarding/manager-1..stdout

@@ -0,0 +1,8 @@
+Connected to a peer
+Connected to a peer
+Connected to a peer
+Got fully_connected event
+Got fully_connected event
+Connected to a peer
+Got fully_connected event
+Got fully_connected event

testing/btest/Baseline/scripts.base.frameworks.cluster.forwarding/proxy-1..stdout

@@ -0,0 +1,3 @@
+Connected to a peer
+Connected to a peer
+Connected to a peer

testing/btest/Baseline/scripts.base.frameworks.cluster.forwarding/proxy-2..stdout

@@ -0,0 +1,3 @@
+Connected to a peer
+Connected to a peer
+Connected to a peer

testing/btest/Baseline/scripts.base.frameworks.cluster.forwarding/worker-1..stdout

@@ -0,0 +1,3 @@
+Connected to a peer
+Connected to a peer
+Connected to a peer

testing/btest/Baseline/scripts.base.frameworks.cluster.forwarding/worker-2..stdout

@@ -0,0 +1,4 @@
+Connected to a peer
+Connected to a peer
+Connected to a peer
+got forwarded event

testing/btest/scripts/base/frameworks/cluster/forwarding.bro

@@ -0,0 +1,105 @@
+# @TEST-SERIALIZE: comm
+#
+# @TEST-EXEC: btest-bg-run manager-1 BROPATH=$BROPATH:.. CLUSTER_NODE=manager-1 bro %INPUT
+# @TEST-EXEC: btest-bg-run proxy-1   BROPATH=$BROPATH:.. CLUSTER_NODE=proxy-1 bro %INPUT
+# @TEST-EXEC: btest-bg-run proxy-2   BROPATH=$BROPATH:.. CLUSTER_NODE=proxy-2 bro %INPUT
+# @TEST-EXEC: btest-bg-run worker-1  BROPATH=$BROPATH:.. CLUSTER_NODE=worker-1 bro %INPUT
+# @TEST-EXEC: btest-bg-run worker-2  BROPATH=$BROPATH:.. CLUSTER_NODE=worker-2 bro %INPUT
+# @TEST-EXEC: btest-bg-wait 30
+# @TEST-EXEC: TEST_DIFF_CANONIFIER=$SCRIPTS/diff-sort btest-diff manager-1/.stdout
+# @TEST-EXEC: btest-diff proxy-1/.stdout
+# @TEST-EXEC: btest-diff proxy-2/.stdout
+# @TEST-EXEC: btest-diff worker-1/.stdout
+# @TEST-EXEC: btest-diff worker-2/.stdout
+
+@TEST-START-FILE cluster-layout.bro
+redef Cluster::nodes = {
+	["manager-1"] = [$node_type=Cluster::MANAGER, $ip=127.0.0.1, $p=37757/tcp],
+	["proxy-1"] = [$node_type=Cluster::PROXY,     $ip=127.0.0.1, $p=37758/tcp, $manager="manager-1"],
+	["proxy-2"] = [$node_type=Cluster::PROXY,     $ip=127.0.0.1, $p=37759/tcp, $manager="manager-1"],
+	["worker-1"] = [$node_type=Cluster::WORKER,   $ip=127.0.0.1, $p=37760/tcp, $manager="manager-1", $interface="eth0"],
+	["worker-2"] = [$node_type=Cluster::WORKER,   $ip=127.0.0.1, $p=37761/tcp, $manager="manager-1", $interface="eth1"],
+};
+@TEST-END-FILE
+
+global fully_connected: event();
+
+global peer_count = 0;
+global peers_lost = 0;
+global fully_connected_nodes = 0;
+
+event forwarded_event()
+	{
+	print "got forwarded event";
+
+	if ( Cluster::node == "manager-1" )
+		print "manager should NOT have raised the forwarded event";
+
+	terminate();
+	}
+
+event ready()
+	{
+	# note that the publishing node, worker-1, will not receive the forwarded
+	# event as Broker's forwarding prevents the message going back to the
+	# immediate sender.
+	Broker::publish("test_topic", forwarded_event);
+	}
+
+event fully_connected()
+	{
+	if ( ! is_remote_event() )
+		return;
+
+	print "Got fully_connected event";
+	fully_connected_nodes = fully_connected_nodes + 1;
+
+	if ( Cluster::node == "manager-1" )
+		{
+		if ( peer_count == 4 && fully_connected_nodes == 4 )
+			Broker::publish(Cluster::node_topic("worker-1"), ready);
+		}
+	}
+
+event bro_init()
+	{
+	Broker::auto_publish(Cluster::manager_topic, fully_connected);
+
+	if ( Cluster::node == "manager-1" )
+		Broker::forward("test_topic");
+	if ( Cluster::node == "worker-1" )
+		Broker::subscribe("test_topic");
+	if ( Cluster::node == "worker-2" )
+		Broker::subscribe("test_topic");
+	}
+
+event Broker::peer_added(endpoint: Broker::EndpointInfo, msg: string)
+	{
+	print "Connected to a peer";
+	peer_count = peer_count + 1;
+
+	if ( Cluster::node == "manager-1" )
+		{
+		if ( peer_count == 4 && fully_connected_nodes == 4 )
+			Broker::publish(Cluster::node_topic("worker-1"), ready);
+		}
+	else
+		{
+		if ( peer_count == 3 )
+			event fully_connected();
+		}
+	}
+
+event Broker::peer_lost(endpoint: Broker::EndpointInfo, msg: string)
+	{
+	++peers_lost;
+
+	if ( Cluster::node == "manager-1" )
+		{
+		if ( peers_lost == 2 )
+			# Both workers terminated
+			terminate();
+		}
+	else
+		terminate();
+	}