support leader election for charms

Bug #1258485 reported by John A Meinel on 2013-12-06
20
This bug affects 4 people
Affects Status Importance Assigned to Milestone
juju-core
High
John A Meinel
cassandra (Juju Charms Collection)
High
Unassigned
postgresql (Juju Charms Collection)
Critical
Unassigned

Bug Description

It is difficult for charms to negotiate amongst each other to decide on a leader. (Unit A may see Units B and C but units B and C do not see eachother)

It should be easy to leverage the central nature of the Juju DB to provide a point of reference for them to collaborate.

The idea is outlined in this doc: https://docs.google.com/document/d/1zDnPK4ZSUI_Je4G2wOThFPqTYVLEJVBVweoSAzIrhHo/edit?pli=1

Marking this as High because we would like to see it in this cycle.

Stuart Bishop (stub) wrote :

Not so much difficult, but impossible. The separate sets of units elect different leaders, and you have a split-brain. You can't resolve this without arbitrarily throwing away information from one of the leaders.

Changed in postgresql (Juju Charms Collection):
status: New → Triaged
importance: Undecided → High
importance: High → Critical
Stuart Bishop (stub) wrote :

Document the limitation in the PostgreSQL charm. Use the new facilities once they are provided by juju.

JuanJo Ciarlante (jjo) on 2014-06-12
Changed in cassandra (Juju Charms Collection):
status: New → Triaged
importance: Undecided → High
Curtis Hovey (sinzui) on 2014-10-28
Changed in juju-core:
importance: High → Medium
Curtis Hovey (sinzui) wrote :
Changed in juju-core:
importance: Medium → High
milestone: none → 1.23-beta4
assignee: nobody → John A Meinel (jameinel)
status: Triaged → Fix Committed
Curtis Hovey (sinzui) on 2015-04-10
Changed in juju-core:
status: Fix Committed → Fix Released
Stuart Bishop (stub) on 2015-08-10
Changed in cassandra (Juju Charms Collection):
status: Triaged → Fix Released
Changed in postgresql (Juju Charms Collection):
status: Triaged → In Progress
Stuart Bishop (stub) on 2015-11-27
Changed in postgresql (Juju Charms Collection):
status: In Progress → Fix Released
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