mirror of https://github.com/schoebel/mars
179 lines
9.0 KiB
Plaintext
179 lines
9.0 KiB
Plaintext
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===================================== CLUSTER ======================================================================
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action pre-conditions post-conditions
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================ ================================================== =============================================
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--------------------------------------------------------------------------------------------------------------------
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1. create no cluster present cluster created
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mars module not inserted /mars mounted
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/mars mounted
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--------------------------------------------------------------------------------------------------------------------
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2. join (1.) on primary host cluster joined
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cluster not joined /mars mounted
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mars module not inserted
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/mars mounted
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--------------------------------------------------------------------------------------------------------------------
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3. leave (1.) or (2.) no cluster present
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no resources existent
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===================================== RESOURCE =====================================================================
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The state of a resource comprises the states of 3 objects (role, disk, replication) taking the following values:
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role: primary secondary
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----
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disk:
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----
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detached : underlying device may be used by other applications
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outdated : role = secondary
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AND consistent
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AND [ not all logfiles have been fetched from the primary
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OR primary_unreachable ]
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uptodate : consistent
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AND [ role = primary OR [ role = secondary
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AND no logfiles are to be fetched
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AND repl != primary_unreachable] ]
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inconsistent: none of the three states above (a sync, restore or similar action is necessary
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to reach a consistent state)
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repl:
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----
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notjoined : role = secondary AND resource exists on the primary only
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replaying : consistent disk
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AND [ [ role = primary AND can "send" logfiles ]
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OR [ role = secondary AND can receive logfiles ] ]
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primary_unreachable : what the name means
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paused_sync : interrupted while syncing
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syncing : what the name means
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paused_replay : able to replay, but interrupted
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disconnected : not used until now, probably not necessary
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For data consistence the states of the following objects are important too:
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device (the "underlying" device):
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------
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locked : cannot be opened by other applications
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unlocked: usable as a normal block device by other applications
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unused : not used by any application
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mars_device:
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-----------
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usable : can be used in "normal" ways
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invisible: what the name means
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undef : not existent
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===========
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Hint: Of course the states are not independent, e.g.:
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disk != detached => device = locked
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repl = synching && role = secondary => disk inconsistent
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These action independent rules will not be regarded here and must be guaranteed by tests.
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===========
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In the following table the states which are of no interest in the specific
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action are omitted or their values are marked with *.
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The disk state "consistent" is an abreviation for outdated || uptodate
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action pre-conditions post-conditions
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============= ================================================== =================================================
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--------------------------------------------------------------------------------------------------------------------
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4. create
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(1.)
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mars module inserted role : primary
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device: unused disk : uptodate
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repl : replaying
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mars_device : usable
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device : locked
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--------------------------------------------------------------------------------------------------------------------
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5. join
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(4.) on primary host, (2.) role : secondary
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mars module inserted disk : uptodate
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repl : notjoined repl : replaying
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device : unused mars_device : invisible
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device : locked
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--------------------------------------------------------------------------------------------------------------------
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6. leave
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(4.) or (5.) disk : detached
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disk: uptodate mars_device : undef
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outdated device : unlocked
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-> wait | force
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repl: disconnected
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--------------------------------------------------------------------------------------------------------------------
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7. switch primary -> secondary
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(4.) or (5.) role : secondary
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role : primary disk : uptodate
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--------------------------------------------------------------------------------------------------------------------
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8. switch secondary -> primary
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(4.) or (5.) role: primary
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no other primary host (evtl. locking (two mounts!))
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role : secondary
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disk : uptodate
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outdated
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-> wait | force
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--------------------------------------------------------------------------------------------------------------------
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9. pause_sync
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(4.) or (5.) repl: paused_sync
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repl: synching
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!synching
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-> hint
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--------------------------------------------------------------------------------------------------------------------
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10. pause_replay
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(4.) or (5.) repl: paused_replay
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repl: replaying
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!replaying
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-> hint
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--------------------------------------------------------------------------------------------------------------------
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11. invalidate
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(4.) or (5.) disk: inconsistent
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--------------------------------------------------------------------------------------------------------------------
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12. logrotate
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(4.) or (5.) log rotated
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--------------------------------------------------------------------------------------------------------------------
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13. logdelete
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(4.) or (5.) log deleted
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logfile closed
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AND logfile received from all secondaries
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===================================== DEVICES ======================================================================
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--------------------------------------------------------------------------------------------------------------------
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14. attach
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(4.) or (5.) disk: if no "out of mars changes" occured since detach
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disk: detached state = state before detach
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else
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state = inconsistent
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--------------------------------------------------------------------------------------------------------------------
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15. detach
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(4.) or (5.) disk: detached
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--------------------------------------------------------------------------------------------------------------------
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===================================== FURTHER INFOS NEEDED =========================================================
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1. all state infos from remote hosts are to be provided with a timestamp indicating their actuality
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2. replication states like synching, replaying need a "progress bar"
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3. useless actions (e.g. primary on a resource beeing already primary) should be handled as tolerant as possible
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