This is now my fourth attempt to get the message through. Apologies if you see
multiple copies.
I've tried to give as much relevant data as I can think of, but please let me
know if you need any other info. I spent the day getting jmxtrans to talk to
statsd with the cassandra JMX data, so I can provide graphs of just about
anything you want. I can also re-run the tests to replicate the problem if
need be. As always, thanks for taking a look!
I have a 4 host test cluster that I'm writing counters into running 0.8.1, and
I'm writing to it with hector with CL.ONE or CL.QUORUM (test was run with each
and both gave the same results). Partitioner is the RandomPartitioner, and
RF=3. nodetool ring shows that actual data is well balanced:
Address DC Rack Status State Load Owns
Token
127605887595351923798765477786913079296
10.0.0.57 datacenter1 rack1 Up Normal 1.59 GB 25.00% 0
10.0.0.56 datacenter1 rack1 Up Normal 1.39 GB 25.00%
42535295865117307932921825928971026432
10.0.0.55 datacenter1 rack1 Up Normal 1.24 GB 25.00%
85070591730234615865843651857942052864
10.0.0.54 datacenter1 rack1 Up Normal 1.34 GB 25.00%
127605887595351923798765477786913079296
I also tested against a 1-box test cluster with RF=1.
Both show the same results: high performance for a while, and then
ReplicateOnWrite backs way up (I've seen it as high as a million), the
cassandra process becomes unresponsive, and the hector client starts throwing
exceptions. High performance in this case equates to about 5-20k inserts/sec
on both the 4-box and 1-box cluster (I'm inserting one long row at a time, so
the performance is bounded by the one box owning the row). The cassandra
process never seems to recover, even if left for 24 hours. It's still chewing
through those ReplicateOnWrite pending tasks.
GC doesn't seem to be a factor. Logs show GCs completing in < 1s on all 4
boxes in the test cluster, as well as on the 1 standalone server.
I'm also seeing highly erratic performance from the cluster in general:
inserts/sec usually start at around 3k, but then maybe creep up towards 6k,
then drop back down to below 1k for an extended period of time, then maybe 1%
of the time they'll spike up to 8k or even 15k, but that doesn't last more than
30 seconds.
Here's the tpstats output from all 4 boxes:
Slowest/most problematic/highest cpu usage one:
This tpstats output is also representative of the one box cluster about 20
minutes into my insert run.
4 $ ./nodetool -h localhost tpstats
Pool Name Active Pending Completed
ReadStage 0 0 0
RequestResponseStage 0 0 59095840
MutationStage 0 0 31182942
ReadRepairStage 0 0 0
ReplicateOnWriteStage 32 928042 28246716
GossipStage 1 1 449464
AntiEntropyStage 0 0 0
MigrationStage 0 0 4
MemtablePostFlusher 0 0 445
StreamStage 0 0 0
FlushWriter 0 0 445
FILEUTILS-DELETE-POOL 0 0 38
MiscStage 0 0 0
FlushSorter 0 0 0
InternalResponseStage 0 0 4
HintedHandoff 0 0 0
Second highest cpu usage one:
3 $ ./nodetool -h localhost tpstats
Pool Name Active Pending Completed
ReadStage 0 0 0
RequestResponseStage 0 0 27413910
MutationStage 0 0 27523094
ReadRepairStage 0 0 0
ReplicateOnWriteStage 0 0 11111971
GossipStage 0 0 335422
AntiEntropyStage 0 0 0
MigrationStage 0 0 4
MemtablePostFlusher 0 0 66
StreamStage 0 0 0
FlushWriter 0 0 66
FILEUTILS-DELETE-POOL 0 0 31
MiscStage 0 0 0
FlushSorter 0 0 0
InternalResponseStage 0 0 4
HintedHandoff 0 0 0
The other 2 that see minimal cpu usage:
2 $ ./nodetool -h localhost tpstats
Pool Name Active Pending Completed
ReadStage 0 0 0
RequestResponseStage 0 0 9213999
MutationStage 0 0 33233114
ReadRepairStage 0 0 0
ReplicateOnWriteStage 0 0 0
GossipStage 0 0 336016
AntiEntropyStage 0 0 0
MigrationStage 0 0 4
MemtablePostFlusher 0 0 77
StreamStage 0 0 0
FlushWriter 0 0 77
FILEUTILS-DELETE-POOL 0 0 40
MiscStage 0 0 0
FlushSorter 0 0 0
InternalResponseStage 0 0 4
HintedHandoff 0 0 0
1 $ ./nodetool -h localhost tpstats
Pool Name Active Pending Completed
ReadStage 0 0 0
RequestResponseStage 0 0 13796875
MutationStage 0 0 36116662
ReadRepairStage 0 0 0
ReplicateOnWriteStage 0 0 0
GossipStage 0 0 336496
AntiEntropyStage 0 0 0
MigrationStage 0 0 4
MemtablePostFlusher 0 0 91
StreamStage 0 0 0
FlushWriter 0 0 91
FILEUTILS-DELETE-POOL 0 0 43
MiscStage 0 0 0
FlushSorter 0 0 0
InternalResponseStage 0 0 4
HintedHandoff 0 0 0
