From 32473b85b0ce84246cccf516627a0e2d8c6b200b Mon Sep 17 00:00:00 2001
From: Jon Siwek <jsiwek@corelight.com>
Date: Tue, 30 Apr 2019 20:53:38 -0700
Subject: [PATCH] Force the Broker IOSource to idle periodically

Previously, if there was always input in each Process() call, then
the Broker IOSource would never go idle and could completely starve
out a packet IOSource since it would always report readiness with
a timestamp value of the last known network_time (which prevents
selecting a packet IOSource for processing, due to incoming packets
likely having timestamps that are later).
---
 src/broker/Manager.cc | 28 +++++++++++++++++++++++++++-
 src/broker/Manager.h  |  1 +
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/src/broker/Manager.cc b/src/broker/Manager.cc
index ec69308790..bfaa35b2d0 100644
--- a/src/broker/Manager.cc
+++ b/src/broker/Manager.cc
@@ -140,6 +140,7 @@ Manager::Manager(bool arg_reading_pcaps)
 	reading_pcaps = arg_reading_pcaps;
 	after_zeek_init = false;
 	peer_count = 0;
+	times_processed_without_idle = 0;
 	log_topic_func = nullptr;
 	vector_of_data_type = nullptr;
 	log_id_type = nullptr;
@@ -942,7 +943,32 @@ void Manager::Process()
 			}
 		}
 
-	SetIdle(! had_input);
+	if ( had_input )
+		{
+		++times_processed_without_idle;
+
+		// The max number of Process calls allowed to happen in a row without
+		// idling is chosen a bit arbitrarily, except 12 is around half of the
+		// SELECT_FREQUENCY (25).
+		//
+		// But probably the general idea should be for it to have some relation
+		// to the SELECT_FREQUENCY: less than it so other busy IOSources can
+		// fit several Process loops in before the next poll event (e.g. the
+		// select() call ), but still large enough such that we don't have to
+		// wait long before the next poll ourselves after being forced to idle.
+		if ( times_processed_without_idle > 12 )
+			{
+			times_processed_without_idle = 0;
+			SetIdle(true);
+			}
+		else
+			SetIdle(false);
+		}
+	else
+		{
+		times_processed_without_idle = 0;
+		SetIdle(true);
+		}
 	}
 
 
diff --git a/src/broker/Manager.h b/src/broker/Manager.h
index a0520698da..2310189418 100644
--- a/src/broker/Manager.h
+++ b/src/broker/Manager.h
@@ -382,6 +382,7 @@ private:
 	bool reading_pcaps;
 	bool after_zeek_init;
 	int peer_count;
+	int times_processed_without_idle;
 
 	Func* log_topic_func;
 	VectorType* vector_of_data_type;