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.viva...@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.steppac...@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 > >
