observed-remove-map
v3.4.1
Published
Observed-Remove Map replicated data type.
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observed-remove-map
An "Observed-Remove Map" or "OR-Map", is a Map data type that can be modified concurrently and will eventually reach the same state everywhere (it is "eventually consistent").
Built with observed-remove-set.
example
var map1 = new OrMap('bob')
var map2 = new OrMap('alice')
// let's provide a "delay" function to simulate concurrency on a network
function delay (cb) {
setTimeout(cb, 3000) // 3 seconds of delay!
}
// let's "connect" our two maps
map1.on('op', op => delay(() => map2.receive(op)))
map2.on('op', op => delay(() => map1.receive(op)))
// both Bob and Alice simulatenously set "a" to different values
map1.set('a', 0) // {a:0}
map2.set('a', 1) // {a:1}
In a normal Map type, this would cause a conflict! However, these are Or-Maps and will handle conflicts for us. Once all operations have been delivered, both Bob and Alice are guaranteed to have the same data.
// after all operations have been received...
map1.get('a') // 0
map2.get('a') // 0
install
npm install observed-remove-map
<script src="dist/or-map.js"></script>
api
orMap = new OrMap(uuid, [opts])
Create a new OR-Map.
Required uuid
is some universally unique identifer for this map.
Optional opts
object is an object of the form:
{
serialize: (Object) => {}, // custom object serializer
parse: (String) => {}, // custom object deserializer
compareKeys: (Object, Object) => bool, // custom key comparator (returns true if objects are equal)
compareValues(Object, Object) => bool // custom value comparator
}
orMap.add(key)
Add a key to the map with a value of null
.
element
is any serializable Javascript object. Changes to within this object will NOT be replicated.
orMap.delete(key)
Remove a key and it's value from the map.
orMap.set(key, value)
Sets the value at key
. If key
does not exist, it will be added first.
orMap.has(key)
Returns true if the map contains the given key
.
orMap.get(key)
Returns the value associated with the given key
.
orMap.keys()
Returns an array with all keys.
orMap.values()
Returns an array with all values.
orMap.receive(op)
Receive an operation from a remote map. Must be called exactly once per remote operation.
orMap.getState()
Get the complete state of the system. Useful for complete replication to other sites. Not consistency safe without a 2-step sync.
orMap.setState(sate)
Set the complete state of the system (use the state object from getState
). Useful for complete replication to other sites. Not consistency safe without a 2-step sync.
orMap.on('op', function (op) {})
Fires when an operation needs to be sent to connected Maps. Operations can be delivered in any order and more-than-once, but must be delivered at-least-once. There may be multiple operation events for each call to a method.
op
is the operation object that needs to be passed into otherOrMap.receive(op)
for all other replicas.
orMap.on('add', function (key) {})
Fires when a new key is added to the map by a remote operation. (will not fire when orMap.add()
is called locally.)
orMap.on('delete', function (key) {})
Fires when a key is removed from the map by a remote operation. (will not fire when orMap.delete()
is called locally.)
orMap.on('set', function (key, value) {})
Fires when the value associated with a key is changed by a remote operation. (will not fire when orMap.set()
is called locally.)