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From Eric Stevens <migh...@gmail.com>
Subject Re: Thrift client creates massive amounts of network packets
Date Tue, 24 May 2016 17:18:50 GMT
I'm not familiar with Titan's usage patterns for Cassandra, but I wonder if
this is because of the consistency level it's querying Cassandra at - i.e.
if CL isn't LOCAL_[something], then this might just be lots of little
checksums required to satisfy consistency requirements.

On Mon, May 23, 2016 at 7:22 AM Ralf Steppacher <ralf.vivates@gmail.com>
wrote:

> I remembered that Titan treats edges (and vertices?) as immutable and
> deletes the entity and re-creates it on every change.
> So I set the gc_grace_seconds to 0 for every table in the Titan keyspace
> and ran a major compaction. However, this made the situation worse. Instead
> of roughly 2’700 tcp packets per user request before the compaction, the
> same request now results in 5’400 packets. Which is suspiciously close to a
> factor or 2. But I have no idea wha to make of it.
>
> Ralf
>
>
> > On 20.05.2016, at 15:11, Ralf Steppacher <ralf.steppacher@vivates.ch>
> wrote:
> >
> > Hi all,
> >
> > tl:dr
> > The Titan 0.5.4 cassandrathrift client + C* 2.0.8/2.2.6 create massive
> amounts of network packets for multiget_slice queries. Is there a way to
> avoid the “packet storm”?
> >
> >
> > Details...
> >
> > We are using Titan 0.5.4 with its cassandrathrift storage engine to
> connect to a single node cluster running C* 2.2.6 (we also tried 2.0.8,
> which is the version in Titans dependencies). When moving to a
> multi-datacenter setup with the client in one DC and the C* server in the
> other, we ran into the problem that response times from Cassandra/the graph
> became unacceptable (>30s vs. 0.2s within datacenter). Looking at the
> network traffic we saw that the client and server exchange a massive number
> of very small packets.
> > The user action we were tracing yields three packets of type “REPLY
> multiget_slice”. Per such a reply we see about 1’000 of packet pairs like
> this going back and forth between client and server:
> >
> > 968   09:45:55.354613   x.x.x.30 x.x.x.98 TCP   181   54406 → 9160 [PSH,
> ACK] Seq=53709 Ack=39558 Win=1002 Len=115 TSval=4169130400 TSecr=4169119527
> > 0000   00 50 56 a7 d6 0d 00 0c 29 d1 a4 5e 08 00 45 00  .PV.....)..^..E.
> > 0010   00 a7 e3 6d 40 00 40 06 fe 3c ac 13 00 1e ac 13  ...m@.@..<......
> > 0020   00 62 d4 86 23 c8 2c 30 4e 45 1b 4b 0b 55 80 18  .b..#.,0NE.K.U..
> > 0030   03 ea 59 40 00 00 01 01 08 0a f8 7f e1 a0 f8 7f  ..Y@............
> > 0040   b7 27 00 00 00 6f 80 01 00 01 00 00 00 0e 6d 75  .'...o........mu
> > 0050   6c 74 69 67 65 74 5f 73 6c 69 63 65 00 00 3a 38  ltiget_slice..:8
> > 0060   0f 00 01 0b 00 00 00 01 00 00 00 08 00 00 00 00  ................
> > 0070   00 00 ab 00 0c 00 02 0b 00 03 00 00 00 09 65 64  ..............ed
> > 0080   67 65 73 74 6f 72 65 00 0c 00 03 0c 00 02 0b 00  gestore.........
> > 0090   01 00 00 00 02 72 c0 0b 00 02 00 00 00 02 72 c1  .....r........r.
> > 00a0   02 00 03 00 08 00 04 7f ff ff ff 00 00 08 00 04  ................
> > 00b0   00 00 00 01 00                                   .....
> >
> > 969   09:45:55.354825   x.x.x.98 x.x.x.30 TCP   123   9160 → 54406 [PSH,
> ACK] Seq=39558 Ack=53824 Win=1540 Len=57 TSval=4169119546 TSecr=4169130400
> > 0000   00 0c 29 d1 a4 5e 00 50 56 a7 d6 0d 08 00 45 00  ..)..^.PV.....E.
> > 0010   00 6d 19 dd 40 00 40 06 c8 07 ac 13 00 62 ac 13  .m..@.@......b..
> > 0020   00 1e 23 c8 d4 86 1b 4b 0b 55 2c 30 4e b8 80 18  ..#....K.U,0N...
> > 0030   06 04 3b d6 00 00 01 01 08 0a f8 7f b7 3a f8 7f  ..;..........:..
> > 0040   e1 a0 00 00 00 35 80 01 00 02 00 00 00 0e 6d 75  .....5........mu
> > 0050   6c 74 69 67 65 74 5f 73 6c 69 63 65 00 00 3a 38  ltiget_slice..:8
> > 0060   0d 00 00 0b 0f 00 00 00 01 00 00 00 08 00 00 00  ................
> > 0070   00 00 00 ab 00 0c 00 00 00 00 00                 ………..
> >
> > With very few exceptions all packets have the exact same length of 181
> and 123 bytes respectively. The overall response time of the graph query
> grows approx. linearly with the network latency.
> > As even “normal” internet network latencies render the setup useless I
> assume we are doing something wrong. Is there a way to avoid that storm of
> small packets by configuration? Or is Titan’s cassandrathrift storage
> backend to blame for this?
> >
> >
> > Thanks in advance!
> > Ralf
>
>

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