(https://www.cloudping.co/ is a useful place to get inter-region latency in AWS)
On Tue, Oct 17, 2017 at 9:20 PM, Chris Lohfink <clohfin...@gmail.com> wrote: > An alternative if using >3.8 you can use the org.apache.cassandra. > metrics:type=Messaging,name=[DC]-Latency mbean where [DC] is the name of > the DC and you can get the inter DC latency per node (to that node). This > does not account for NTP drift though, just how long it takes messages (ie > mutations) take to get to a node from other DCs. > > Chris > > On Tue, Oct 17, 2017 at 7:18 PM, Jon Haddad <j...@jonhaddad.com> wrote: > >> I recommend figuring out the latency between your datacenters. Cassandra >> isn’t going to be any more than that barring JVM pauses on the remote >> coordinator. >> >> >> On Oct 17, 2017, at 4:17 PM, Bill Walters <billwalter...@gmail.com> >> wrote: >> >> Hi Everyone, >> >> I need some suggestions on finding the time taken for Cassandra >> replication to happen from east to west region for write and read >> operations on a multi DC cluster. >> Currently, below is our cluster setup. >> >> *Cassandra version:* DSE 5.0.7 >> *No of Data centers:* 2 (AWS East and AWS West regions) >> *No of Nodes:* 12 nodes (6 nodes in AWS East and 6 nodes in AWS West) >> *Replication Factor:* 3 in each data center. >> *Cluster size*: Around 40 GB on each node >> >> Sometime, next year we have an activity where our clients are going to be >> reading only from AWS West region. The data center in AWS east will be >> available but we do not want any reads to be done on this.(Our management >> wants to know the time it takes for Cassandra to replicate from one DC to >> the other) >> >> Here are some options I have thought of in finding the time taken for >> Cassandra replication to happen from AWS East DC to AWS West DC. >> >> 1. Setup a Java client to write/read a transaction with *"Local Quorum" >> *consistency >> level in* AWS East* region as Local data center, capture the time taken >> for this activity. Similarly use this client to perform read/write >> transaction with *"Local Quorum"* consistency level in *AWS West* region >> and capture the time. Then finally perform the same transaction with with >> *"Each >> Quorum" *consistency level and capture the time. >> >> *Inter DC latency* = *Time taken for Each Quorum transaction* *-* *(Time >> taken for Local Quorum transaction in AWS East as local dc)* *-** (Time >> taken for Local Quorum transaction in AWS West as local dc)*. >> >> >> 2. Utilize the https://github.com/gitaroktato/cassandra-replication- >> latency-tools open source project where a Python Cassandra clients >> writes in one Data Center and other client reads in other data center. >> >> >> Can you please suggest if my strategies above will help in finding the >> Inter DC latency or there are other ways I need to follow. >> >> >> Thank You, >> Bill Walters. >> >> >> > -- Ben Wood Software Engineer - Data Agility Mesosphere
