Broker::publish: Warn on using Broker::publish() when inactive

This is mostly for transitioning base scripts to Cluster::publish() and
avoid silent surprises why certain things don't work when using ZeroMQ.

src/broker/Manager.h

@@ -109,7 +109,7 @@ public:
     /**
      * Returns true if any Broker communication is currently active.
      */
-    [[deprecated("Remove with v8.1 - unused")]] bool Active();
+    bool Active();
 
     /**
      * Advances time.  Broker data store expiration is driven by this

src/broker/messaging.bif

@@ -57,8 +57,14 @@ static bool publish_event_args(ArgsSpan args, const zeek::String* topic,
                                zeek::detail::Frame* frame)
 	{
 	zeek::Broker::Manager::ScriptScopeGuard ssg;
+	zeek::ScriptLocationScope scope{frame};
+
 	auto rval = false;
 
+	if ( zeek::broker_mgr != zeek::cluster::backend && ! zeek::broker_mgr->Active() )
+		zeek::reporter->Warning("Non-broker cluster backend configured and Broker manager inactive. "
+                                        "Did you mean to use Cluster::publish() instead of Broker::publish()?");
+
 	if ( args[0]->GetType()->Tag() == zeek::TYPE_RECORD )
 		rval = zeek::broker_mgr->PublishEvent(topic->CheckString(),
 		                                      args[0]->AsRecordVal());

testing/btest/Baseline/cluster.broker.publish-warning/..manager..stderr

@@ -0,0 +1,4 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+warning in ../manager.zeek, line 8: Non-broker cluster backend configured and Broker manager inactive. Did you mean to use Cluster::publish() instead of Broker::publish()?
+warning in ../manager.zeek, line 16: Non-broker cluster backend configured and Broker manager inactive. Did you mean to use Cluster::publish() instead of Broker::publish()?
+received termination signal

testing/btest/Baseline/cluster.broker.publish-warning/..manager.out

@@ -0,0 +1,3 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+node_up, worker-1
+node_down, worker-1

testing/btest/Baseline/cluster.broker.publish-warning/..worker.out

@@ -0,0 +1,2 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+node_up, manager

testing/btest/cluster/broker/publish-warning.zeek

@@ -0,0 +1,61 @@
+# @TEST-DOC: When using ZeroMQ, Broker::publish() produces a warning.
+#
+# @TEST-REQUIRES: have-zeromq
+#
+# @TEST-GROUP: cluster-zeromq
+#
+# @TEST-PORT: XPUB_PORT
+# @TEST-PORT: XSUB_PORT
+# @TEST-PORT: LOG_PULL_PORT
+#
+# @TEST-EXEC: cp $FILES/zeromq/cluster-layout-simple.zeek cluster-layout.zeek
+# @TEST-EXEC: cp $FILES/zeromq/test-bootstrap.zeek zeromq-test-bootstrap.zeek
+#
+# @TEST-EXEC: btest-bg-run manager "ZEEKPATH=$ZEEKPATH:.. && CLUSTER_NODE=manager zeek -b ../manager.zeek >out"
+# @TEST-EXEC: btest-bg-run worker "ZEEKPATH=$ZEEKPATH:.. && CLUSTER_NODE=worker-1 zeek -b ../worker.zeek >out"
+#
+# @TEST-EXEC: btest-bg-wait 30
+# @TEST-EXEC: btest-diff ./manager/out
+# @TEST-EXEC: btest-diff ./manager/.stderr
+# @TEST-EXEC: btest-diff ./worker/out
+
+
+# @TEST-START-FILE common.zeek
+@load ./zeromq-test-bootstrap
+
+global finish: event(name: string);
+# @TEST-END-FILE
+
+# @TEST-START-FILE manager.zeek
+@load ./common.zeek
+# If a node comes up that isn't us, send it a finish event.
+event Cluster::node_up(name: string, id: string) {
+	print "node_up", name;
+	Cluster::publish(Cluster::nodeid_topic(id), finish, Cluster::node);
+
+	# Also via broker, but this produces a warning which we test for.
+	Broker::publish(Cluster::nodeid_topic(id), finish, Cluster::node);
+}
+
+# If the worker vanishes, finish the test.
+event Cluster::node_down(name: string, id: string) {
+	print "node_down", name;
+
+	# Do another Broker::publish(), just for the kicks.
+	Broker::publish(Cluster::nodeid_topic(id), finish, Cluster::node);
+
+	terminate();
+}
+# @TEST-END-FILE
+
+# @TEST-START-FILE worker.zeek
+@load ./common.zeek
+
+event Cluster::node_up(name: string, id: string) {
+	print "node_up", name;
+}
+
+event finish(name: string) &is_used {
+	terminate();
+}
+# @TEST-END-FILE