[CASSANDRA-3833] support arbitrary topology transitions

• Type: New Feature
• Status: Resolved
• Priority: Normal
• Resolution: Later
• Assignee: Peter Schuller
• Reporter: Peter Schuller

Authors

Peter Schuller

• Created: 01/Feb/12 23:45
• Updated: 16/Apr/19 09:32
• Resolved: 09/Jul/13 16:18

Description

Once we have the locator abstracted (with the gossiper being a
particular concrete implementation), we want to change the locator
abstraction to not express changes in ring topology on a per-node
basis; rather we want to use an abstraction which communicates two
arbitrary ring states; one state for the read set, and one for the
write set.

Once this abstraction is in place, the (pluggable) locator will be
able to make bulk changes to a ring at once. Main points:

• Must be careful in handling consistency level during ring
  transitions, such that a given node in the read set corresponds to a
  specific node in the write set. This will impose some restrictions
  on completion of transitions, to avoid code complexity, so it is an
  important point.

• All code outside of gossip (and any other locator that works
  similarly) will be agnostic about individual changes to nodes, and
  will instead only be notified when new ring states are available (in
  aggregate). This makes the change non-trivial because all code that
  currently is oriented around individual node changes always
  producing a valid ring, will have to be changed.

Issue Links

• depends upon: CASSANDRA-3834 make locator pluggable/abstract
• is related to: CASSANDRA-3901 write endpoints are not treated correctly, breaking consistency guarantees
• is related to: CASSANDRA-3892 improve TokenMetadata abstraction, naming - audit current uses
• relates to: CASSANDRA-3483 Support bringing up a new datacenter to existing cluster without repair