Interval tree clock

Version: 0.1.0

Authors: Nyiro, Gergo (gergo.nyiro@gmail.com).

References

Interval tree clock (itc) is a good candidate for a logical clock in a distributed system where the members join and leave the cluster very often.

Itc offers the following actions:

Initialize a clock:

1> ClockA0 = itc:seed().
{1,0}

Create clock for a new cluster member:

2> [ClockA1, ClockB1] = itc:fork(ClockA0).
[{{1,0},0},{{0,1},0}]

The order of the clocks (ClockA0, ClockA1, ClockB1) cannot be determied.

3> itc:leq(ClockA0, ClockA1).
true
4> itc:leq(ClockA1, ClockA0).
true

An event has to be executed to increment the clocks.

5> ClockA2 = itc:event(ClockA1).
{{1,0},{0,1,0}}
6> ClockB2 = itc:event(ClockB1).
{{0,1},{0,0,1}}

So the clocks can be ordered:

7> itc:leq(ClockA0, ClockA2).
true
8> itc:leq(ClockA2, ClockA0).
false

If the cluster nodes are synchronized then the clocks can be joined

9> ClockC3 = itc:join(ClockA2, ClockB2).
{1,1}
10> itc:leq(ClockA2, ClockC3).
true

and the new clock can be used in the syncronized nodes.

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