Getting Netty client related error in storm topology and worker restarting - apache-storm

Question

Version Info:
"org.apache.storm" % "storm-core" % "1.2.1"
"org.apache.storm" % "storm-kafka-client" % "1.2.1"
I have a storm Topology with 3 bolts(A,B,C), Where the middle bolt takes around 450ms mean time and other two bolts takes less than 1ms.
I am running topology with following parallelism hint values on two machines:
A: 4
B: 700
C: 10
I am getting following error after few minutes of topology starting:
in worker log:
2018-07-04T20:16:28.835+05:30 Client [ERROR] discarding 7 messages because the Netty client to Netty-Client-/ip:6700 is being closed
in supervisor logs:
2018-07-04 20:16:29.468 o.a.s.d.s.BasicContainer [INFO] Worker Process 32bc11c0-a1d0-4593-a91a-3ff788ea041a exited with code: 20
2018-07-04 20:16:31.592 o.a.s.d.s.Slot [WARN] SLOT 6700: main process has exited
2018-07-04 20:16:31.592 o.a.s.d.s.Container [INFO] Killing 2825cbe9-aedd-4f10-a796-4f9dc30ae72f:32bc11c0-a1d0-4593-a91a-3ff788ea041a
2018-07-04 20:16:31.600 o.a.s.u.Utils [INFO] Error when trying to kill 7422. Process is probably already dead.
2018-07-04 20:16:32.600 o.a.s.d.s.Slot [INFO] STATE RUNNING msInState: 391195 topo:myTopo-1-1530715184 worker:32bc11c0-a1d0-4593-a91a-3ff788ea041a -> KILL_AND_RELAUNCH msInState: 0 topo:myTopo-1-1530715184 worker:32bc11c0-a1d0-4593-a91a-3ff788ea041a
2018-07-04 20:16:32.600 o.a.s.d.s.Container [INFO] GET worker-user for 32bc11c0-a1d0-4593-a91a-3ff788ea041a
I see similar question asked here and here, I have few queries related to this:
Why is this error coming and how to resolve?
How to get more debug information from Storm, I have already set conf.setDebug(true)
Is there some limitation/guidelines around how much parallelism factor os OK for a bolt on n number of machines?
Edit:
Logs for strace -fp PID -e trace=read,write,network,signal,ipc in gist. Some relevant looking part is when above thing happends, but however I see such SIGSEGV many places in strace output :
[pid 23635] --- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_ACCERR, si_addr=0x7f83af6f1180} ---
[pid 23549] <... read resumed> "PK\3\4\n\0\0\0\10\0\364J\336F\222'\202\312\310\2\0\0\16\5\0\0\36\0\0\0", 30) = 30
[pid 23654] --- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_ACCERR, si_addr=0x7f83af6f1f80} ---
[pid 23549] read(23, "\235TmW\22A\24~\6\224\227u\vE4\255,JR\300WP\322\0245TH\23\313\3j\347"..., 712) = 712
[pid 23654] rt_sigreturn({mask=[QUIT]}) = 140203560738688
[pid 23635] rt_sigreturn({mask=[QUIT]}) = 140203560735104
strace output of worker process is here, relevant looking logs here:
[pid 24435] recvfrom(291, "HTTP/1.1 200 OK\r\nContent-Type: a"..., 8192, 0, NULL, NULL) = 544
[pid 23473] write(3, "Heap\n garbage-first heap total"..., 347) = 347
[pid 24434] +++ exited with 20 +++
[pid 24405] +++ exited with 20 +++
[pid 24435] +++ exited with 20 +++
[pid 24427] +++ exited with 20 +++
Edit 2:
There is this question as well: Connection refused error in worker logs - apache storm : as par it's answer not setting storm.local.hostname might cause it, but it is already set for me.
There is another bug filed here having similar netty error, which is also still unresolved.