Network communication (via Netty)

Scenario

When Flink runs a job, data transmission and reverse pressure detection between tasks depend on Netty. In certain environments, Netty parameters should be configured.

Configuration Description

For advanced optimization, you can modify the following Netty configuration items. The default configuration can meet the requirements of tasks of large-scale clusters with high concurrent throughput. For details about the parameters, visit the Netty official website at http://netty.io/.

**Table 1** Parameter description
Parameter	Description	Default Value	Mandatory
taskmanager.network.netty.num-arenas	Number of Netty memory blocks.	1	No
taskmanager.network.netty.server.numThreads	Number of Netty server threads	1	No
taskmanager.network.netty.client.numThreads	Number of Netty client threads	1	No
taskmanager.network.netty.client.connectTimeoutSec	Netty client connection timeout duration. Unit: second	120	No
taskmanager.network.netty.sendReceiveBufferSize	Size of Netty sending and receiving buffers. This defaults to the system buffer size (cat /proc/sys/net/ipv4/tcp_[rw]mem) and is 4 MB in modern Linux. Unit: byte	4096	No
taskmanager.network.netty.transport	Netty transport type, either nio or epoll	nio	No