> I don't think these are exposed by any nodetool commands though, but you can > use any JMX client to read them. They are sort of shown by nodetool proxyhistograms though not in aggregate.
Cheers ----------------- Aaron Morton Cassandra Consultant New Zealand @aaronmorton http://www.thelastpickle.com On 30/07/2013, at 2:16 AM, Richard Low <rich...@wentnet.com> wrote: > On 29 July 2013 14:43, Langston, Jim <jim.langs...@compuware.com> wrote: > > Running nodetool and looking at the cfstats output, for the > counters such as write count and read count, do those numbers > reflect any replication ? > > For instance, if write count shows 3000 and the replication factor > is 3, is that really 1000 writes ? > > The counts are the number of operations that particular node has processed. > So if you sum up all the write counts across all node's cfstats output, it > will be a factor of replication factor too high, assuming all replicas > received all writes. (A write message will be sent to all replicas, but if > one is down or busy it may not get processed.) > > If your cluster is balanced, then you can estimate the total number of write > operations from one cfstats output as > > count * num_nodes / replication_factor > > So, as in your example, if one node shows write count 3000 and you have RF 3 > with e.g. 3 nodes, your cluster will have processed about 3000 writes. > > Reads are a bit harder, because, unlike writes, not all nodes necessarily > receive all read requests. It depends on consistency level, snitch and value > of read_repair_chance. You can estimate how many nodes will be involved in > each read request though to figure out how many reads have actually been > submitted. > > However, I think the numbers exposed by StorageProxyMBean > getWriteOperations() and getReadOperations() would give you the true number > (when summed up over all nodes). These numbers don't over count for > replication since they count client requests. I don't think these are > exposed by any nodetool commands though, but you can use any JMX client to > read them. > > Richard.
