Home | Table of Contents | NodeA Cannot Establish TCP Connection (Port 7800 by Default) to NodeB | CloverETL 4.6.1
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### NodeA Cannot Establish TCP Connection (Port 7800 by Default) to NodeB

TCP connection is used for asynchronous messaging. When the NodeB can't send/receive asynchronous messages, the other nodes aren't notified about started/finished jobs, so parent jobflow running on NodeA keeps waiting for the event from NodeB. Heart-beat is vital for meaningful load-balancing, the same check-task mentioned above also checks heart-beat from all cluster nodes.

##### Time-line describing the scenario:

- 0s network connection between NodeA and NodeB is down

- 60s NodeA uses the last available NodeB heart-beat

- 0-40s check-task running on NodeA detects missing heart-beat from NodeB

- status of NodeA or NodeB (the one with shorter uptime) is changed to “suspended”

##### The following configuration properties serve to tune time intervals mentioned above:

- `cluster.node.check.checkMinInterval` - periodicity of cluster node checks (40000ms by default)

- `cluster.node.sendinfo.interval` – periodicity of heart-beat messages (2000ms by default)

- `cluster.node.sendinfo.min_interval` – the heart-beat may occasionally be sent more often than specified by “cluster.node.sendinfo.interval”, this property specifies minimum interval (500ms by default)

- `cluster.node.remove.interval` – maximum interval for missing heart-beat (50000ms by default)

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