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https://issues.apache.org/jira/browse/HADOOP-1395?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sameer Paranjpye updated HADOOP-1395:
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Component/s: mapred
> Implement a generic DFA
> ------------------------
>
> Key: HADOOP-1395
> URL: https://issues.apache.org/jira/browse/HADOOP-1395
> Project: Hadoop
> Issue Type: New Feature
> Components: mapred
> Reporter: Arun C Murthy
> Assignee: Arun C Murthy
> Fix For: 0.14.0
>
> Attachments: HADOOP-1395_1_20070521.patch
>
>
> Owen alluded to it HADOOP-1183 and Devaraj talked about this in HADOOP-1337
> ... I believe this will be a generally useful feature in other parts of
> hadoop too...
> The proposal is to implement a generic state machine which can be configured
> as needed and could be used to track states/transitions of various entities.
> This will hopefully make code less complex (for e.g. in the shuffle) and more
> maintainable/understandable since the state transitions of entities will be
> visible in one place (for e.g. where it is configured) and not scattered
> across myriad sections.
> The idea is quite simple:
> class StateMachine {
> // Register a legal 'transition' from pre to post state on a given event
> and
> // a user-provided hook/callback
> void registerTransition(State pre, State post, Event event, Hook hook)
> throws IllegalStateTransitionException;
> // Effect a transition from the state on the event, return the resulting
> state or
> // throw an exception if the transition is illegal.
> // cause/victim are user objects i.e. context/result of the transition.
> State doTransition(State state, Event event, Object cause, Object victim)
> throws IllegalStateTransitionException;
> }
> -*-*-
> Thoughts?
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