Kill diskless fork child asap when the last replica drop

[enjoy-binbin]

We originally checked the replica connection to whether to kill the
diskless child only when rdbPipeReadHandler is triggered. Actually
we can check it when the replica is disconnected, so that we don't
have to wait for rdbPipeReadHandler to be triggered and can kill
the forkless child as soon as possible.

In this way, when the child or rdbPipeReadHandler is stuck for some
reason, we can kill the child faster and release the fork resources.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.66%. Comparing base (55bbbe0) to head (bd6eb2e).
Report is 1 commits behind head on unstable.

Additional details and impacted files

@@             Coverage Diff              @@
##           unstable    #1227      +/-   ##
============================================
- Coverage     70.66%   70.66%   -0.01%     
============================================
  Files           114      114              
  Lines         63143    63144       +1     
============================================
- Hits          44623    44620       -3     
- Misses        18520    18524       +4     

Files with missing lines	Coverage Δ
src/networking.c	88.50% <100.00%> (+0.01%)	⬆️
src/replication.c	87.37% <100.00%> (-0.02%)	⬇️

... and 8 files with indirect coverage changes

[ranshid]

@enjoy-binbin generally looks good to me. I think there are no tests checking the logs for 0 replicas left during bgsave. Maybe worth adding a test to read and validate the correct logs are issued in that case?

[enjoy-binbin]

generally looks good to me. I think there are no tests checking the logs for 0 replicas left during bgsave. Maybe worth adding a test to read and validate the correct logs are issued in that case?

sorry i forgot to reply. Diskless rdb transfer, last replica dropped, killing fork child you are saying we don't have test to cover this case?

i see we do have a test diskless $all_drop replicas drop during rdb pipe that are checking this log

[ranshid]

generally looks good to me. I think there are no tests checking the logs for 0 replicas left during bgsave. Maybe worth adding a test to read and validate the correct logs are issued in that case?

sorry i forgot to reply. Diskless rdb transfer, last replica dropped, killing fork child you are saying we don't have test to cover this case?

i see we do have a test diskless $all_drop replicas drop during rdb pipe that are checking this log

Don't know how I missed it :) good to go