[jira] [Created] (CASSANDRA-7667) Improve migration

["Robert Stupp (JIRA)" <ji...@apache.org>]

Robert Stupp created CASSANDRA-7667:
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             Summary: Improve migration
                 Key: CASSANDRA-7667
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7667
             Project: Cassandra
          Issue Type: Improvement
            Reporter: Robert Stupp


Idea is to optimize migration especially for large clusters with multiple DCs.
 
Currently {{MigrationManager.announce()}} simply broadcasts to all nodes.
 
Idea is to not announce schema migration to every node.
 
*Against remote DCs*: only contact a single node in each remote DC. This could make migration faster, because network latency comes into play. And it lowers cross-DC network requirements (since 1-to-all communication creates a huge amount of TCP connections). Drawback: remote-DC-announcement must be reliable (receiver must ACK - if it doesn't, sender must retry another node).
 
*Within the local DC*: use some gossip approach - e.g. only contact N nodes at once. Not sure about this one  - it might be nice, if there are really many (~100) nodes in one DC. But it's a bit difficult to guarantee, that all nodes will receive the announcement without giving up the "fire-and-forget" approach.




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