We have libraries that send to a local node director (amf, imm) and others that 
send to a possibly remote server (ntf, log). We need to understand if a send to 
a local node director can fail (I think it can, investigating it).

Can we generally in the library do a send retry or should we just return 
TRYAGAIN?

In the AMF library returning TRYAGAIN is not so good since it can have bad 
consequences and clients are not used to get TRYAGAIN (although they should we 
need to avoid it).


---

** [tickets:#641] MDS resend**

**Status:** unassigned
**Created:** Thu Nov 28, 2013 09:40 AM UTC by Hans Feldt
**Last Updated:** Thu Nov 28, 2013 10:09 AM UTC
**Owner:** nobody

Occasionally we see TIPC link congestion at the sending node. This can be seen 
with "tipc-config -ls" as in:

Link <1.1.1:eth0-1.1.2:eth0>
  ACTIVE  MTU:1500  Priority:10  Tolerance:1500 ms  Window:100 packets
  RX packets:1877 fragments:0/0 bundles:0/0
  TX packets:17511 fragments:0/0 bundles:0/0
  TX profile sample:489 packets  average:151 octets
  0-64:0% -256:97% -1024:0% -4096:3% -16354:0% -32768:0% -66000:0%
  RX states:12974 probes:5918 naks:0 defs:0 dups:0
  TX states:12148 probes:6230 naks:0 acks:0 dups:0
  Congestion bearer:0 link:12  Send queue max:81 avg:0

Above is from testing with tipc-pipe. With the default link window at 50 I get 
one send EAGAIN when sending 100 msgs. When I increase link window to 100 I can 
burst 100 msgs without link congestion. If I then burst 1000 msgs I see lots of 
link congestion.


If we transfer this to opensaf it means a failed MDS send. MDS does not do any 
resends, neither does any service (IMMs FEVS not considered)

AMFd for example could loose a message to a node director which is very bad.

What I suggest is that messages should be resent, typically a loop with 3 
retries with a 100ms sleep in between.

There are some concerns, like:
* Can we put this in MDS or should it be done per service?
* What about MDS/TCP, same problem there?


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