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Posted to commits@cassandra.apache.org by "mck (JIRA)" <ji...@apache.org> on 2019/08/05 17:18:00 UTC
[jira] [Updated] (CASSANDRA-15260) Add `allocate_tokens_for_dc_rf`
yaml option for token allocation
[ https://issues.apache.org/jira/browse/CASSANDRA-15260?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
mck updated CASSANDRA-15260:
----------------------------
Description:
Similar to DSE's option: {{allocate_tokens_for_local_replication_factor}}
Currently the [ReplicationAwareTokenAllocator|https://www.datastax.com/dev/blog/token-allocation-algorithm] requires a defined keyspace and a replica factor specified in the current datacenter.
This is problematic in a number of ways. The real keyspace can not be used when adding new datacenters as, in practice, all its nodes need to be up and running before it has the capacity to replicate data into it. New datacenters (or lift-and-shifting a cluster via datacenter migration) therefore has to be done using a dummy keyspace that duplicates the replication strategy+factor of the real keyspace. This gets even more difficult come version 4.0, as the replica factor can not even be defined in new datacenters before those datacenters are up and running.
These issues are removed by avoiding the keyspace definition and lookup, and presuming the replica strategy is by datacenter, ie NTS, with the introduction of an {{allocate_tokens_for_dc_rf}} option.
It may also be of value considering whether {{allocate_tokens_for_dc_rf=3}} becomes the default, as this is the replication factor for the vast majority of datacenters in production. I suspect this would be a good improvement over the existing randomly generated tokens algorithm.
Initial patch is available in [https://github.com/thelastpickle/cassandra/commit/fc4865b0399570e58f11215565ba17dc4a53da97]
The patch does not remove the existing {{allocate_tokens_for_keyspace}} option, as it still provides the codebase for handling different replication strategies.
was:
Similar to option in DSE `allocate_tokens_for_local_replication_factor`
Currently the [ReplicationAwareTokenAllocator|https://www.datastax.com/dev/blog/token-allocation-algorithm] requires a defined keyspace and a replica factor specified in the current datacenter.
This is problematic in a number of ways. Come version 4.0 the replica factor can not be defined in new datacenters before those datacenters are up and running. Previously even real keyspaces could not be used as a new datacenter has to, in practice, have all its nodes up and running before it has the capacity to replicate data into it. New datacenters, or lift-and-shifting a cluster via datacenter migration, can be done using a dummy keyspace that duplicates the replication strategy and factor of the real keyspace.
This issues are reduced by avoiding the keyspace definition and lookup, and presuming the replica strategy is by datacenter, ie NTS, with the introduction of an `allocate_tokens_for_dc_rf` option.
It may also be of value considering whether `allocate_tokens_for_dc_rf=3` is the default, as this is the replication factor for the vast majority of datacenters in production. I suspect this would be a good improvement over the existing randomly generated tokens algorithm.
Initial patch is available in https://github.com/thelastpickle/cassandra/commit/fc4865b0399570e58f11215565ba17dc4a53da97
> Add `allocate_tokens_for_dc_rf` yaml option for token allocation
> ----------------------------------------------------------------
>
> Key: CASSANDRA-15260
> URL: https://issues.apache.org/jira/browse/CASSANDRA-15260
> Project: Cassandra
> Issue Type: Improvement
> Components: Local/Config
> Reporter: mck
> Assignee: mck
> Priority: Normal
>
> Similar to DSE's option: {{allocate_tokens_for_local_replication_factor}}
> Currently the [ReplicationAwareTokenAllocator|https://www.datastax.com/dev/blog/token-allocation-algorithm] requires a defined keyspace and a replica factor specified in the current datacenter.
> This is problematic in a number of ways. The real keyspace can not be used when adding new datacenters as, in practice, all its nodes need to be up and running before it has the capacity to replicate data into it. New datacenters (or lift-and-shifting a cluster via datacenter migration) therefore has to be done using a dummy keyspace that duplicates the replication strategy+factor of the real keyspace. This gets even more difficult come version 4.0, as the replica factor can not even be defined in new datacenters before those datacenters are up and running.
> These issues are removed by avoiding the keyspace definition and lookup, and presuming the replica strategy is by datacenter, ie NTS, with the introduction of an {{allocate_tokens_for_dc_rf}} option.
> It may also be of value considering whether {{allocate_tokens_for_dc_rf=3}} becomes the default, as this is the replication factor for the vast majority of datacenters in production. I suspect this would be a good improvement over the existing randomly generated tokens algorithm.
> Initial patch is available in [https://github.com/thelastpickle/cassandra/commit/fc4865b0399570e58f11215565ba17dc4a53da97]
> The patch does not remove the existing {{allocate_tokens_for_keyspace}} option, as it still provides the codebase for handling different replication strategies.
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