#Module unsplit_vclock#
A simple Erlang implementation of vector clocks as inspired by Lamport logical clocks.
Copyright (c) 2007-2008 Basho Technologies
Authors: Justin Sheehy (justin@basho.com), Andy Gross (andy@basho.com).
References* Leslie Lamport (1978). "Time, clocks, and the ordering of events in a distributed system". Communications of the ACM 21 (7): 558-565.
- Friedemann Mattern (1988). "Virtual Time and Global States of Distributed Systems". Workshop on Parallel and Distributed Algorithms: pp. 215-226
##Data Types##
###counter()##
counter() = integer()
###node()##
node() = term()
Nodes can have any term() as a name, but they must differ from each other.
###timestamp()##
timestamp() = integer()
###vc_entry()##
vc_entry() = {node(), {counter(), timestamp()}}
The timestamp is present but not used, in case a client wishes to inspect it.
###vclock()##
vclock() = [vc_entry]
##Function Index##
| all_nodes/1 | Return the list of all nodes that have ever incremented VClock. |
| descends/2 | Return true if Va is a direct descendant of Vb, else false -- remember, a vclock is its own descendant! |
| equal/2 | Compares two VClocks for equality. |
| fresh/0 | Create a brand new vclock. |
| get_counter/2 | Get the counter value in VClock set from Node. |
| get_timestamp/2 | Get the timestamp value in a VClock set from Node. |
| increment/2 | Increment VClock at Node. |
| merge/1 | Combine all VClocks in the input list into their least possible common descendant. |
| prune/3 | Possibly shrink the size of a vclock, depending on current age and size. |
##Function Details##
###all_nodes/1##
all_nodes(VClock::vclock()) -> [node()]
Return the list of all nodes that have ever incremented VClock.
###descends/2##
descends(Va::vclock(), Vb::vclock()) -> bool()
Return true if Va is a direct descendant of Vb, else false -- remember, a vclock is its own descendant!
###equal/2##
equal(VClockA::vclock(), VClockB::vclock()) -> true | false
Compares two VClocks for equality. Not very fast.
###fresh/0##
fresh() -> vclock()
###get_counter/2##
get_counter(Node::node(), VClock::vclock()) -> counter()
Get the counter value in VClock set from Node.
###get_timestamp/2##
get_timestamp(Node::node(), VClock::vclock()) -> timestamp()
Get the timestamp value in a VClock set from Node.
###increment/2##
increment(Node::node(), VClock::vclock()) -> vclock()
###merge/1##
merge(VClocks::[vclock()]) -> vclock()
Combine all VClocks in the input list into their least possible common descendant.
###prune/3##
prune(V::vclock(), Now::integer(), BucketProps::term()) -> vclock()
Possibly shrink the size of a vclock, depending on current age and size.