44 lines
1.5 KiB
Scala
44 lines
1.5 KiB
Scala
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/**
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* Copyright (C) 2015 Typesafe Inc. <http://www.typesafe.com>
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*/
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package akka.cluster.ddata
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/**
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* INTERNAL API
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*
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* Optimization for add/remove followed by merge and merge should just fast forward to
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* the new instance.
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*
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* It's like a cache between calls of the same thread, you can think of it as a thread local.
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* The Replicator actor invokes the user's modify function, which returns a new ReplicatedData instance,
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* with the ancestor field set (see for example the add method in ORSet). Then (in same thread) the
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* Replication calls merge, which makes use of the ancestor field to perform quick merge
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* (see for example merge method in ORSet).
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*
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* It's not thread safe if the modifying function and merge are called from different threads,
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* i.e. if used outside the Replicator infrastructure, but the worst thing that can happen is that
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* a full merge is performed instead of the fast forward merge.
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*/
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private[akka] trait FastMerge { self: ReplicatedData ⇒
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private var ancestor: FastMerge = null
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/** INTERNAL API: should be called from "updating" methods */
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private[akka] def assignAncestor(newData: T with FastMerge): T = {
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newData.ancestor = if (this.ancestor eq null) this else this.ancestor
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this.ancestor = null // only one level, for GC
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newData
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}
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/** INTERNAL API: should be used from merge */
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private[akka] def isAncestorOf(that: T with FastMerge): Boolean =
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that.ancestor eq this
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/** INTERNAL API: should be called from merge */
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private[akka] def clearAncestor(): self.type = {
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ancestor = null
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this
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}
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}
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