Hi hackers,
Bgwriter process will call `pgstat_send_bgwriter` to send statistics to stat
collector, but stat collector is not started when standby is not in hot standby
mode.
```
if (pmState == PM_RUN || pmState == PM_HOT_STANDBY)
PgStatPID = pgstat_start();
```
This would lead to the kernel Recv-Q buffer being filled up by checking
`netstat -du`.
I think we should disable to send statistics in `pgstat_send_bgwriter` when
stat collector is not running. So here are three questions about how to fix it.
1. Is there any way we could effectively check the status of stat collector
in bgwriter process?
2. Is there any way we check the bgwriter is running on a standby but not in
hot stanby mode?
3. Is there any other process will send statistics except the bgwriter in
standby? We should fix it one by one or add a check in `pgstat_send` directly?
Thanks,
Hubert Zhang
