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@ -1,7 +1,11 @@
# Odering in OrbitList # Odering in OrbitList
Ordering in OrbitList is done with Interval Tree Clocks (https://github.com/ricardobcl/Interval-Tree-Clocks). Each node tracks a global sequence *seq* and a local version *ver*. When an item is added to a list, local version *ver* is increased by 1. Whenever a list is *joined* with another list (eg. upon sync), the global sequence *seq* is set to *Max(global.seq, local.seq)*. When adding an item to the list, the item has a reference to all *heads* where *head* is an item that is not referenced by any other item in the list.
### Graph
``` ```
A B C A B C
0.0 0.0
| |
0.0 0.1 0.0 0.1
@ -20,6 +24,7 @@
<--- Sync ALL <--- Sync ALL
``` ```
### Evolution of the state
Initial state: Initial state:
``` ```
A = [] A = []
@ -27,12 +32,13 @@ B = []
C = [] C = []
``` ```
Two nodes add events concurrently: ***Two nodes add events concurrently***
Add items to A: Add items to A:
``` ```
listA.add("mango") listA.add("mango")
listA.add("banana") listA.add("banana")
// "A": [ // "A": [
// { "id": "A", "seq": 0, "ver": 0, "prev": null} // { "id": "A", "seq": 0, "ver": 0, "prev": null}
// { "id": "A", "seq": 0, "ver": 1, "prev": ["A.0.0"]} // { "id": "A", "seq": 0, "ver": 1, "prev": ["A.0.0"]}
@ -44,6 +50,7 @@ Add items to C:
listC.add("apple") listC.add("apple")
listC.add("strawberry") listC.add("strawberry")
listC.add("orange") listC.add("orange")
// "C": [ // "C": [
// { "id": "C", "seq": 0, "ver": 0, "prev": null} // { "id": "C", "seq": 0, "ver": 0, "prev": null}
// { "id": "C", "seq": 0, "ver": 1, "prev": ["C.0.0"]} // { "id": "C", "seq": 0, "ver": 1, "prev": ["C.0.0"]}
@ -53,14 +60,15 @@ listC.add("orange")
B receives a 'sync' from A and C: B receives a 'sync' from A and C:
``` ```
Sync: B <--> A B.join(A)
Sync: B <--> C B.join(C)
``` ```
Add items to B: Add items to B:
``` ```
listB.add("pineapple") listB.add("pineapple")
listB.add("papaya") listB.add("papaya")
// "B": [ // "B": [
// { "id": "A", "seq": 0, "ver": 0, "prev": null} // { "id": "A", "seq": 0, "ver": 0, "prev": null}
// { "id": "A", "seq": 0, "ver": 1, "prev": ["A.0.0"]} // { "id": "A", "seq": 0, "ver": 1, "prev": ["A.0.0"]}
@ -74,11 +82,12 @@ listB.add("papaya")
A receives a 'sync' from B: A receives a 'sync' from B:
``` ```
Sync: A <--> B A.join(B)
``` ```
``` ```
listA.add("kiwi") listA.add("kiwi")
// "B": [ // "B": [
// { "id": "A", "seq": 0, "ver": 0, "prev": null} // { "id": "A", "seq": 0, "ver": 0, "prev": null}
// { "id": "A", "seq": 0, "ver": 1, "prev": ["A.0.0"]} // { "id": "A", "seq": 0, "ver": 1, "prev": ["A.0.0"]}
@ -93,11 +102,12 @@ listA.add("kiwi")
C receives a 'sync' from A: C receives a 'sync' from A:
``` ```
Sync: C <--> A C.join(A)
``` ```
``` ```
listC.add("blueberry") listC.add("blueberry")
// "C": [ // "C": [
// { "id": "A", "seq": 0, "ver": 0, "prev": null} // { "id": "A", "seq": 0, "ver": 0, "prev": null}
// { "id": "A", "seq": 0, "ver": 1, "prev": ["A.0.0"]} // { "id": "A", "seq": 0, "ver": 1, "prev": ["A.0.0"]}
@ -113,11 +123,11 @@ listC.add("blueberry")
A receives a 'sync' from C, B receives a 'sync' from C: A receives a 'sync' from C, B receives a 'sync' from C:
``` ```
Sync: A <--> C A.join(C)
Sync: B <--> C B.join(C)
``` ```
Data set converged (after sync ALL): Converged data set:
```json ```json
{ "id": "A", "seq": 0, "ver": 0, "prev": null}, { "id": "A", "seq": 0, "ver": 0, "prev": null},
{ "id": "A", "seq": 0, "ver": 1, "prev": ["A.0.0"]}, { "id": "A", "seq": 0, "ver": 1, "prev": ["A.0.0"]},