---

id: cluster-config-stream title: Stream Manager sidebar_label: Stream Manager

You can configure the Stream Manager (SM) in a topology using the parameters below, including how the SM handles back pressure.

Back Pressure Parameters

Parameter	Meaning	Default
heron.streammgr.network.backpressure.threshold	The number of times the SM should wait to see a buffer full while enqueueing data before declaring the start of backpressure	3
heron.streammgr.network.backpressure.highwatermark.mb	The high water mark on the number of megabytes that can be left outstanding on a connection	50
heron.streammgr.network.backpressure.lowwatermark.md	The low water mark on the number of megabytes that can be left outstanding on a connection	30
heron.streammgr.network.options.maximum.packet.mb	The maximum packet size, in megabytes, for the SM's network options	100

Timeout Interval

Parameter	Meaning	Default
heron.streammgr.xormgr.rotatingmap.nbuckets	TODO	3

Other Parameters

Parameter	Meaning	Default
heron.streammgr.packet.maximum.size.bytes	Maximum size (in bytes) of packets sent out from the SM	102400
heron.streammgr.cache.drain.frequency.ms	The frequency (in milliseconds) at which the SM's tuple cache is drained	10
heron.streammgr.cache.drain.size.mb	The size threshold (in megabytes) at which the SM's tuple cache is drained	100
heron.streammgr.client.reconnect.interval.sec	The reconnect interval to other SMs for the SM client (in seconds)	1
heron.streammgr.client.reconnect.tmaster.interval.sec	The reconnect interval to the Topology Master for the SM client (in seconds)	10
heron.streammgr.tmaster.heartbeat.interval.sec	The interval (in seconds) at which a heartbeat is sent to the Topology Master	10
heron.streammgr.connection.read.batch.size.mb	The maximum batch size (in megabytes) at which the SM reads from the socket	1
heron.streammgr.connection.write.batch.size.mb	The maximum batch size (in megabytes) to write by the stream manager to the socket	1