On Wed, Jan 17, 2018 at 4:21 AM, kurt greaves <k...@instaclustr.com> wrote:
> I believe you are able to get away with just altering the keyspace to > include both DC's even before the DC exists, and then adding your nodes to > that new DC using the algorithm. Note you'll probably want to take the > opportunity to reduce the number of vnodes to something reasonable. Based > off memory from previous testing you can get a good token balance with 16 > vnodes if you have at least 6 nodes per rack (with RF=3 and 3 racks). > Alexander, Kurt, Thank you for the suggestions. None of them did work in the end, unfortunately: 1. Using auto_bootstrap=false always results in random token allocation, ignoring the allocate_tokens_for_keyspace option. The token allocation option is only considered if shouldBootstrap() returns true: https://github.com/apache/cassandra/blob/cassandra-3.0.15/src/java/org/apache/cassandra/service/StorageService.java#L790 if (shouldBootstrap()) { https://github.com/apache/cassandra/blob/cassandra-3.0.15/src/java/org/apache/cassandra/service/StorageService.java#L842 BootStrapper.getBootstrapTokens() (the only place in code using the token allocation option) https://github.com/apache/cassandra/blob/cassandra-3.0.15/src/java/org/apache/cassandra/service/StorageService.java#L901 else { ... 2. Using auto_bootstrap=true and allocate_tokens_for_keyspace=data_ks gives us balanced range ownership on the new empty DC. The problem though, is that rebuilding of an already bootstrapped node doesn't work: the node believes that it already has all the data. We are going to proceed by manually assigning a small number of tokens to the nodes in new DC with auto_bootstrap=false and only use the automatic token allocation when we need to scale it out. This seems to be the only supported way to use it anyway. Regards, -- Alex
