问题
As a follow up of this Data Partition in Cassandra, I got the idea of the vNodes. Thanks to 'Simon Fontana Oscarsson'
When I try to explore the data partitioning using vNodes, I have few questions,
I try to observe the partition distribution in 2 node (./nodetool ring)
Two seed nodes (2 node)
172.30.56.61 rack1 Up Normal 105.19 KiB 100.00% -9207297847862311651
172.30.56.61 rack1 Up Normal 105.19 KiB 100.00% -9185516104965672922
172.30.56.61 rack1 Up Normal 105.19 KiB 100.00% -9135483708655236026
172.30.56.60 rack1 Up Normal 102.77 KiB 100.00% -9106737079237505681
172.30.56.61 rack1 Up Normal 105.19 KiB 100.00% -9078521344187921602
172.30.56.61 rack1 Up Normal 105.19 KiB 100.00% -9051897156173923903
172.30.56.61 rack1 Up Normal 105.19 KiB 100.00% -9049800264451581717
172.30.56.61 rack1 Up Normal 105.19 KiB 100.00% -9039572936575206977
172.30.56.60 rack1 Up Normal 102.77 KiB 100.00% -9019927187583981555
172.30.56.60 rack1 Up Normal 102.77 KiB 100.00% -9006071175095726599
172.30.56.60 rack1 Up Normal 102.77 KiB 100.00% -8995415525773810853
172.30.56.60 rack1 Up Normal 102.77 KiB 100.00% -8949342263103866059
172.30.56.61 rack1 Up Normal 105.19 KiB 100.00% -8880432529087253108
172.30.56.61 rack1 Up Normal 105.19 KiB 100.00% -8859265089807316498
172.30.56.61 rack1 Up Normal 105.19 KiB 100.00% -8844286905987198633
172.30.56.61 rack1 Up Normal 105.19 KiB 100.00% -8832739468389117376
So as per my observation in two nodes, The Node 61 has the values from -9207297847862311651 to -9185516104965672922 as one range goes on...
NOTE : Partition range from '-9039572936575206977' to '-9019927187583981554' is currently handled by Node 61.
Now I am adding one more node to the cluster (not the seed node) and I ran ./nodetool ring,
Two seed nodes with one new node (3 node)
172.30.56.61 rack1 Up Normal 104.12 KiB 64.73% -9207297847862311651
172.30.56.61 rack1 Up Normal 104.12 KiB 64.73% -9185516104965672922
172.30.56.61 rack1 Up Normal 104.12 KiB 64.73% -9135483708655236026
172.30.56.60 rack1 Up Normal 102.77 KiB 63.57% -9106737079237505681
172.30.56.61 rack1 Up Normal 104.12 KiB 64.73% -9078521344187921602
172.30.56.61 rack1 Up Normal 104.12 KiB 64.73% -9051897156173923903
172.30.56.61 rack1 Up Normal 104.12 KiB 64.73% -9049800264451581717
172.30.56.61 rack1 Up Normal 104.12 KiB 64.73% -9039572936575206977
172.30.56.62 rack1 Up Normal 103.7 KiB 71.70% -9031848008695747480
172.30.56.62 rack1 Up Normal 103.7 KiB 71.70% -9028974600706382491
172.30.56.60 rack1 Up Normal 102.77 KiB 63.57% -9019927187583981555
Now I observed that same partition range is given to the new node Node 62, i.e, range from -9039572936575206977 to -9031848008695747480 is handled by Node 61 but -9031848008695747480 to -9019927187583981555 is handled by Node 62 (New node),
1) So does this mean that, adding a new node in the cluster will distribute the existing partition range?
2) Is there a way to observe the replicated partitions in Cassandra using any utility like nodetool?
3) I have 3 nodes with RF as 2, How to see the data's available in a node 62 alone?
回答1:
1) When adding a node Cassandra will start by choosing good ranges for the new node to take over. It will then create 256 new token ranges that are just portions of the already existing ones. This means the new node takes tokens from many nodes (instead of only one per RF when not using vnodes) in the cluster which makes streaming alot faster.
2 and 3) Does this answer your questions? determine node of a partition in Cassandra
来源：https://stackoverflow.com/questions/47628499/data-re-partitioning-in-cassandra