When a datahost(all write/read host) drop packets,the query will hang for a while until TCP timout

[yanhuqing666]

When a datahost(all write/read host) drop packets (use iptables or other)，
and the “dataNodeHeartbeatPeriod” is very small，means heartbeat konws this thing.
A query send to the datahost will also hang for timeout.
the time is decided by RTO and net.ipv4.tcp_syn_retries.
TIMEOUT = RTO * (POWER(2, retries+1)-1)

[irene-coming]

PS:
if heartbeat has not verified the drop packets problem, then:
for new connection: syspara net.ipv4.tcp_syn_retries = 6, matters how long the client wait
for exists connection: both syspara net.ipv4.tcp_retries2 = 15 and dble config:<property name="sqlExecuteTimeout">300</property> , matters how long the client wait