[Spread-users] spread daemon hangs after running for a few days

chanh hua dawginlife at yahoo.com
Tue Mar 11 18:04:11 EDT 2008


john, 

when a daemon goes into a bad state, it doesn't just stutter, but stops working completely; however, other daemon in the cluster still functions correctly.

i did some further testing and the massive drops only occur btw these two servers.  if i used spsend and sprecv against any one of this server and another machine not defined in the segment, the drop comes down to the amount you specified.  so the drops is somehow confined to this segment.  will need to do some more digging.

looking at sptmonitor output, the "retrans" to "sent pack" seems high. do you think there is a network issue or configuration problem?



============================
Status at as-phl-cbiis4 V 3.17. 3 (state 1, gstate 1) after 74354 seconds :
Membership  :  4  procs in 2 segments, leader is as-ny-cbapps2
rounds   :   42454      tok_hurry :   38124     memb change:       9
sent pack:       6      recv pack :    3040     retrans    :       0
u retrans:       0      s retrans :       0     b retrans  :       0
My_aru   :    2745      Aru       :    2745     Highest seq:    2745
Sessions :       0      Groups    :      33     Window     :      60
Deliver M:    1595      Deliver Pk:    3048     Pers Window:      15
Delta Mes:    1595      Delta Pack:    2745     Delta sec  :   74354
==================================

Monitor>
============================
Status at as-phl-cbiis1 V 3.17. 4 (state 1, gstate 1) after 73908 seconds :
Membership  :  4  procs in 2 segments, leader is as-ny-cbapps2
rounds   :   21796      tok_hurry :   37928     memb change:       4
sent pack:    1708      recv pack :    1137     retrans    :    1291
u retrans:      37      s retrans :       0     b retrans  :    1254
My_aru   :    2745      Aru       :    2745     Highest seq:    2745
Sessions :       9      Groups    :      56     Window     :      60
Deliver M:    1595      Deliver Pk:    2944     Pers Window:      15
Delta Mes:       0      Delta Pack:       0     Delta sec  :    -446
==================================

Monitor>
============================
Status at as-ny-cbsql3 V 3.17. 3 (state 1, gstate 1) after 74106 seconds :
Membership  :  4  procs in 2 segments, leader is as-ny-cbapps2
rounds   :   42313      tok_hurry :   37997     memb change:       6
sent pack:       5      recv pack :    3072     retrans    :       0
u retrans:       0      s retrans :       0     b retrans  :       0
My_aru   :    2745      Aru       :    2745     Highest seq:    2745
Sessions :       0      Groups    :      19     Window     :      60
Deliver M:    1595      Deliver Pk:    3040     Pers Window:      15
Delta Mes:       0      Delta Pack:       0     Delta sec  :     198
==================================

Monitor>
============================
Status at as-ny-cbapps2 V 3.17. 4 (state 1, gstate 1) after 73982 seconds :
Membership  :  4  procs in 2 segments, leader is as-ny-cbapps2
rounds   :   21797      tok_hurry :   37970     memb change:       4
sent pack:    1145      recv pack :    1714     retrans    :     739
u retrans:     109      s retrans :      37     b retrans  :     593
My_aru   :    2745      Aru       :    2745     Highest seq:    2745
Sessions :      20      Groups    :      56     Window     :      60
Deliver M:    1595      Deliver Pk:    3028     Pers Window:      15
Delta Mes:       0      Delta Pack:       0     Delta sec  :    -124
==================================


John Schultz <jschultz at spreadconcepts.com> wrote: On Tue, 11 Mar 2008, chanh hua wrote:

> Bring me to my question, what network property is the misses data 
> suppose to tell us?

The misses data tells you how many of the sent packets the receiver missed 
(i.e. - didn't receive).  From your report it looks like the sender sent 
10000 packets but the receiver only heard 1999 (10000 - 8001) of them 
before it got the last packet.  If correct, then that would be about an 
80% loss rate for your configuration.  A typical loss rate for LAN 
broad/multicast is well below 1%.

> The explanation he gave for why we might have observed all
> these misses was b/c the broadcast address used contains all
> network machines(i.e. desktops, printers, etc...) and not
> just servers and most of those machines ignore broadcast.
> But since he doesn't know what these results mean, he can't
> say for sure.

He is correct that broadcast will bother (i.e. - potentially increase 
load) all the machines on the associated subnet.  If you instead use 
multicast, then either your switch/router or you NICs should filter out 
the packets before an interrupt is generated on non-participating 
machines.  Multicast is preferable, however, occasionally some switches 
and routers don't implement multicast well or their multicast is 
misconfigured.  In such situations, broadcast sometimes works better due 
to its simplicity.

> If this is an issue, would using a multicast address be better? 
> However, when i used a multicast address for the test, i still saw a lot 
> of misses.

Typically, broadcast should not increase loss versus multicast unless your 
switch/router is biased against broadcast somehow for some weird reason.

> I talked to the network admin, and he's not seeing any drops
> btw the servers on the segments.  And he confirmed the
> broadcast address i used was correct.

Well, it definitely seems like something is wrong from your reports.  Try 
using spmonitor to view the status of the daemons as they are running. 
Like I said, if you see their retrans counts going up by more than a 
couple a second, then something is probably wrong in your network.

> would having a lot of drops lead cause daemon to be unresponsive?

Theoretically, it could.  If the daemons got stuck in a loop of trying to 
establish a membership due to intermittent / flaky communications with 
other daemons, then the system would appear to freeze as the daemons stop 
processing client communications in this state.  Usually, the "freeze"
wouldn't persist forever but rather you would see lots of daemon 
membership changes and progress would stutter forward.

Cheers!

---
John Schultz
Spread Concepts
Phn: 443 838 2200


       
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