[ https://issues.apache.org/jira/browse/CASSANDRA4598?page=com.atlassian.jira.plugin.system.issuetabpanels:alltabpanel
]
Julien Lambert updated CASSANDRA4598:

Description:
On a 2 nodecluster, if the two tokens are close enough, the ownership information displayed
will be 0.00% for each, instead of ~0% for one and ~100% for the other. The number of replicas
displayed is then 0, even if you have more.
Reproduce:
 Create a 2node cluster, using Murmur3Partitioner
 Move the tokens to two consecutive values
 Display ring with nodetool
Problem:
This line causing this problem is in {{describeOwnership()}} of {{Murmur3Partitioner.java}}
(lines 117 and 123):
{{float age = ((ti  tim1 + ri) % ri) / ri;}}
If {{ti  tim1}} (the difference of the two consecutive tokens) is too small, then the precision
of the float isn't enough to represent the exact numbers (because {{ri}}, the total range
of the ring, is a very big number).
For example, {{(float) (ri + 1) = (float) (ri  1) = (float) ri = 9.223372E18}}, so that {{((ri+1)%ri)/ri
= ((ri1)%ri)/ri = (ri%ri)/ri = 0}}. Whereas with a correct precision, the exact value for
{{(ri1)%ri}} should be {{ri1}} and {{(ri1)/ri ~ 1.0 (100%)}} instead of 0%.
Also, as the number of replica is determined by NodeCmd using the ownership percentages, it
is wrong too.
Solution:
We might want to use BigInteger or BigDecimal somewhere?
was:
On a 2 nodecluster, if the two tokens are close enough, the ownership information displayed
will be 0.00% for each, instead of ~0% for one and ~100% for the other.
Reproduce:
 Create a 2node cluster, using Murmur3Partitioner
 Move the tokens to two consecutive values
 Display ring with nodetool
Problem:
This line causing this problem is in {{describeOwnership()}} of {{Murmur3Partitioner.java}}
(lines 117 and 123):
{{float age = ((ti  tim1 + ri) % ri) / ri;}}
If {{ti  tim1}} (the difference of the two consecutive tokens) is too small, then the precision
of the float isn't enough to represent the exact numbers (because {{ri}}, the total range
of the ring, is a very big number).
For example, {{(float) (ri + 1) = (float) (ri  1) = (float) ri = 9.223372E18}}, so that {{((ri+1)%ri)/ri
= ((ri1)%ri)/ri = (ri%ri)/ri = 0}}. Whereas with a correct precision, the exact value for
{{(ri1)%ri}} should be {{ri1}} and {{(ri1)/ri ~ 1.0 (100%)}} instead of 0%.
Solution:
We might want to use BigInteger or BigDecimal somewhere?
> describeOwnership() in Murmur3Partitioner.java doesn't work for close tokens
> 
>
> Key: CASSANDRA4598
> URL: https://issues.apache.org/jira/browse/CASSANDRA4598
> Project: Cassandra
> Issue Type: Bug
> Affects Versions: 1.2.0
> Reporter: Julien Lambert
> Priority: Minor
>
> On a 2 nodecluster, if the two tokens are close enough, the ownership information displayed
will be 0.00% for each, instead of ~0% for one and ~100% for the other. The number of replicas
displayed is then 0, even if you have more.
> Reproduce:
>  Create a 2node cluster, using Murmur3Partitioner
>  Move the tokens to two consecutive values
>  Display ring with nodetool
> Problem:
> This line causing this problem is in {{describeOwnership()}} of {{Murmur3Partitioner.java}}
(lines 117 and 123):
> {{float age = ((ti  tim1 + ri) % ri) / ri;}}
> If {{ti  tim1}} (the difference of the two consecutive tokens) is too small, then the
precision of the float isn't enough to represent the exact numbers (because {{ri}}, the total
range of the ring, is a very big number).
> For example, {{(float) (ri + 1) = (float) (ri  1) = (float) ri = 9.223372E18}}, so that
{{((ri+1)%ri)/ri = ((ri1)%ri)/ri = (ri%ri)/ri = 0}}. Whereas with a correct precision, the
exact value for {{(ri1)%ri}} should be {{ri1}} and {{(ri1)/ri ~ 1.0 (100%)}} instead of
0%.
> Also, as the number of replica is determined by NodeCmd using the ownership percentages,
it is wrong too.
> Solution:
> We might want to use BigInteger or BigDecimal somewhere?

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