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From Apache Wiki <wikidi...@apache.org>
Subject [Cassandra Wiki] Update of "ConfigurationNotes" by JonHermes
Date Fri, 25 Mar 2011 20:55:56 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Cassandra Wiki" for change notification.

The "ConfigurationNotes" page has been changed by JonHermes.
http://wiki.apache.org/cassandra/ConfigurationNotes?action=diff&rev1=5&rev2=6

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  Per-node options are loaded from yaml and held in !DatabaseDescriptor.
  
- Per-KS, per-CF, and per-Column options are loaded from the !MigrationsTable at startup and
are encapsulated with KSMetaData, CFMetaData, and ColumnDefinition objects, which are held
by !DatabaseDescriptor as well as !Tables and !ColumnFamilyStores respectively. When a migration
arrives, it writes to the !MigrationsTable, then propogates the changes out to the KS/CFMD
objects in the system.
+ Per-KS, per-CF, and per-Column options are loaded from the !MigrationsTable at startup and
are encapsulated with KSMetaData, CFMetaData, and !ColumnDefinition objects, which are held
by !DatabaseDescriptor as well as !Tables and !ColumnFamilyStores respectively. When a migration
arrives, it writes to the !MigrationsTable, then propogates the changes out to the KS/CFMD
objects in the system.
  
  Configuration can be changed at runtime without a restart (excluding the ones that change
on-disk format (which cannot be changed without clearing the cluster) and ones that change
routing). For per-node options, poke !StorageService via JMX (which in turn pokes !DatabaseDescriptor).
For per-KS options, poke the appropriate !Table. For per-CF and per-Column options, poke the
appropriate !ColumnFamilyStore. These ephemeral changes are stronger than migrations (they
stay set regardless of new config coming in), but do not persist between reboots.
  

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