On-disk formats, or even data structure formats, may be changed during an upgrade. Services wishing to do so, may so do it via the PaxosService::upgrade_format() call path. There is no formalized, unified format versioning; the PaxosService class keeps track of its format_version through a key in the store, assumed an unsigned int, but it will be the service’s responsibility to give meaning to those versions.



versions are represented with a single unsigned int. By default, the value zero represents the absence of a formal upgraded format. The first format version was introduced in Dumpling; clusters upgrading to Dumpling saw their format version being increased from zero to one.:

0 to 1 - introduced in v0.65, dev release for v0.67 dumpling
1 to 2 - introduced in v12.0.2, dev release for luminous
2 to 3 - introduced in mimic

0 - all clusters pre-dumpling
1 - all clusters dumpling+ and pre-luminous
2 - all clusters luminous+ and pre-mimic
3 - all clusters mimic+

version 1: introduces new-style monitor caps (i.e., profiles)
version 2: introduces mgr caps and bootstrap-mgr key
version 3: creates all bootstrap and admin keys if they don't yet exist


format_version set on PaxosService::refresh()::

- initially called from Monitor::refresh_from_paxos
  - initially called from Monitor::init_paxos()
    - initially called from Monitor::preinit()

AuthMonitor::upgrade_format() called by PaxosService::_active()::

- called from C_Committed callback, from PaxosService::propose_pending()
- called from C_Active callback, from PaxosService::_active()
- called from PaxosService::election_finished()

- on a freshly deployed cluster, upgrade_format() will be first called
  *after* create_initial().
- on an existing cluster, upgrade_format() will be called after the first

- upgrade_format() is irrelevant on a freshly deployed cluster, as there is
  no format to upgrade at this point.

boil down

  • if format_version >= current_version then format is uptodate, return.
  • if features doesn’t contain LUMINOUS then current_version = 1
  • else if features doesn’t contain MIMIC then current_version = 2
  • else current_version = 3

if format_version == 0::

- upgrade to format version 1
  - move to new-style monitor caps (i.e., profiles):
    - set daemon profiles for existing entities
    - set profile for existing bootstrap keys

if format_version == 1::

- upgrade to format version 2
  - for existing entities:
    - add new cap for mgr
  - for existing 'mgr' entities, fix 'mon' caps due to bug from kraken
    setting 'allow \*', and set 'allow profile mgr' instead.
  - add bootstrap-mgr key.

if format_version == 2::

- upgrade to format version 3
  - create all bootstrap keys if they don't currently exist