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The "Hbase/MasterRewrite" page has been changed by stack. http://wiki.apache.org/hadoop/Hbase/MasterRewrite?action=diff&rev1=4&rev2=5 -------------------------------------------------- Initial Master Rewrite design came of conversations had at the hbase hackathon held at StumbleUpon, August 5-7, 2009 ([[https://issues.apache.org/jira/secure/attachment/12418561/HBase+Hackathon+Notes+-+Sunday.pdf|Jon Gray kept notes]]). The umbrella issue for the master rewrite is [[https://issues.apache.org/jira/browse/HBASE-1816|HBASE-1816]]. Timeline is hbase 0.20.1. == What does the Master do now? == + Here's a bit of a refresher on what Master currently does: - * Splitting - * Should be distributed * Region Assignment - * Balancing + * On startup and balancing as regions are created and deleted as regions grow and split. * Scan root/meta * Make sure Regions are online * Delete parents if no reference * Manage schema alter/online/offline * Admin + * Distributes out administered close, flush, compact messages - * Close region - * Flush - * Compact/Major compact * Watches ZK for its own lease and for regionservers so knows when to run recovery + + == Problems with current Master == + * Balancer is not testable unless you spin up full cluster + * State transitions are not atomic; various messaging sequences can produce confused cluster state. == Design ==
