broker integration: add remote logging

It now works a bit differently than before: whether to send a remote log
write is now a property of the logging stream, not the logging filter
and it's now up the the receiver side filters to instantiate the desired
writer.  i.e. the sender now has no say in what the receiver should use
as the log writer backend.

Under the new style of remote logging, the "Log::enable_remote_logging"
option is repurposed to set the default behavior for new logging
streams.  There's also "Comm::{enable,disable}_remote_logging()" to
explicitly set the desired behavior for a given logging stream.  To
receive remote logs, one calls "Comm::subscribe_to_logs(<topic>)", where
senders implicitly use topics of the form "bro/log/<stream id>".

src/logging/Manager.cc

@@ -16,6 +16,10 @@
 #include "WriterBackend.h"
 #include "logging.bif.h"
 
+#ifdef ENABLE_BROKER
+#include "comm/Manager.h"
+#endif
+
 using namespace logging;
 
 struct Manager::Filter {
@@ -69,6 +73,11 @@ struct Manager::Stream {
 
 	WriterMap writers;	// Writers indexed by id/path pair.
 
+#ifdef ENABLE_BROKER
+	bool enable_remote;
+	int remote_flags;
+#endif
+
 	~Stream();
 	};
 
@@ -287,6 +296,11 @@ bool Manager::CreateStream(EnumVal* id, RecordVal* sval)
 	streams[idx]->event = event ? event_registry->Lookup(event->Name()) : 0;
 	streams[idx]->columns = columns->Ref()->AsRecordType();
 
+#ifdef ENABLE_BROKER
+	streams[idx]->enable_remote = internal_val("Log::enable_remote_logging")->AsBool();
+	streams[idx]->remote_flags = broker::PEERS;
+#endif
+
 	DBG_LOG(DBG_LOGGING, "Created new logging stream '%s', raising event %s",
 		streams[idx]->name.c_str(), event ? streams[idx]->event->Name() : "<none>");
 
@@ -828,6 +842,11 @@ bool Manager::Write(EnumVal* id, RecordVal* columns)
 #endif
 		}
 
+#ifdef ENABLE_BROKER
+	if ( stream->enable_remote )
+		comm_mgr->Log(id, columns, stream->remote_flags);
+#endif
+
 	Unref(columns);
 
 	if ( error )
@@ -1206,6 +1225,53 @@ void Manager::Terminate()
 		}
 	}
 
+#ifdef ENABLE_BROKER
+
+bool Manager::EnableRemoteLogs(EnumVal* stream_id, int flags)
+	{
+	auto stream = FindStream(stream_id);
+
+	if ( ! stream )
+		return false;
+
+	stream->enable_remote = true;
+	stream->remote_flags = flags;
+	return true;
+	}
+
+bool Manager::DisableRemoteLogs(EnumVal* stream_id)
+	{
+	auto stream = FindStream(stream_id);
+
+	if ( ! stream )
+		return false;
+
+	stream->enable_remote = false;
+	return true;
+	}
+
+bool Manager::RemoteLogsAreEnabled(EnumVal* stream_id)
+	{
+	auto stream = FindStream(stream_id);
+
+	if ( ! stream )
+		return false;
+
+	return stream->enable_remote;
+	}
+
+RecordType* Manager::StreamColumns(EnumVal* stream_id)
+	{
+	auto stream = FindStream(stream_id);
+
+	if ( ! stream )
+		return nullptr;
+
+	return stream->columns;
+	}
+
+#endif
+
 // Timer which on dispatching rotates the filter.
 class RotationTimer : public Timer {
 public: